matching the drive train to the engine combo

grumpyvette

Administrator
Staff member
HEY GRUMPYVETTE?

I'm building a mild performance, 9:1 static CR, 350 for my 55 and looking into camshaft choices...I understand the intake closing point (degrees) will affect the dynamic compression ratio (DCR)....My question is what DCR should I be shooting for? and what rear gear and stall speed should I get?
heat, torque levels and shock loads are what kills transmissions
be wary of places that advertise transmission strength based on HORSEPOWER and not TORQUE CAPACITY
while a 2.87:1-3.08:1 rear gear if far from ideal for a performance application,and yes displacement does mater,as does the transmission gearing and/or converter stall speed, a great deal of the throttle response and the effect your carbs flow rate has on the torque curve,will be related too the cam timing, the engines
If your running an automatic transmission and torque converter, that torque converter does not know if you have it installed behind a mild 307 SBC or a performance 502 BBC, the effective stall will depend a great deal on the available torque the engine produces, and yes the mild 307 SBC will stall out at a lower rpm than a performance 502 BBC,with the same torque converter.
one very good reason to talk with the torque converter manufacturers tech dept before selecting a converter and NOT just looking at the rated stall speeds listed in a catalog.
compression ratio, the intake manifold design, and how your throttle is employed (IE an experienced driver can do a great deal to influence the way the car responds, an experienced driver that knows his cars characteristics can do a good deal to maximize acceleration.)
yes you can improve acceleration with a higher numerically rear differential ratio like a 3.73:1-4.11:1 gear especially with an over drive transmission, and a 2600 rpm-3200 rpm stall converter,
yes I have to admit that when I personally swapped from a stock stall speed converter
,in my 383 sbc corvette and a 3200 rpm stall speed converter the difference in performance was amazingly better.
swap too a 3.73:1 rear gear and you've noticeably further enhanced that seat of the pants and slam in the back acceleration.
people tend to not fully appreciate the fact that the performance cars drive train gearing, power to weight ratio and the converter stall
(in the case of automatic transmission) must match the engine torque curve if the car is to perform to anything close to its best potential.
while a manual transmission like a muncie has traditionally been used in performance muscle cars , the current technology with a higher than stock stall speed converter and a decently strong auto transmission like a properly built TH400 or $l80E makes the rather common 450-500 hp 383 small block a much more reasonable combo, with decent durability.
Ive built dozens of 383-406 SBC engines and properly configured and assembled 383-406 SBC engines are fully able to shred a stock 700r4/700r style auto transmission, over time as both transmissions were designed to operate with engines providing no more than 400 ft lbs of torque.

reading links and sub links will help
(and yes its likely to take a day or two to do so!)

generally youll want the transmission first gear ratio multiplied times the rear gear ratio to fall in the 10:1-10.75:1 range
as a general guide its usually suggested that for street performance use, the transmission first gear ratio times the rear gear ratio falls in the 10:1-10.75:1 range
most current auto transmissions have one or even two, over drive gear ratios, thus a rear gear ratio that would severely limit top speeds with a 1 to 1 top gear are no longer as big an issue
and ideally the 70 mph cruise rpm to fall at the lower end of the most effective torque curve, and yes this usually requires an over drive top gear ratio.
but its the driver who controls a good deal of the cars ability to put power effectively to the pavement. and the ability to match the cam timing, intake design and properly tune the combo you have is critical.
READ THE LINKS AND USE THE CALCULATORS PROVIDED
http://vexer.com/automotive-tools/1-4-mile-ET-HP-MPH-calculator

http://www.wallaceracing.com/et-hp-mph.php


http://garage.grumpysperformance.co...late-gear-ratios-and-when-to-shift-calcs.555/

http://garage.grumpysperformance.co...-info-worth-reading-through.11528/#post-53210

https://robrobinette.com/et.htm


http://hotrodworks.net/hotrodmath/quarter.html

http://www.ajdesigner.com/fl_horsepower_elapsed_time/horsepower_elapsed_time.php

http://www.tuneruniversity.com/blog/2012/03/power-to-weight-ratio/


https://www.ringpinion.com/calculators/Calc_RPM.aspx

the formula for HORSEPOWER is
torque/times/ rpm divided by 5252=hp

think about that a second

350 ft lbs at 6500 rpm= 433 hp

500 ft lbs at 4500 rpm=428 hp
the stock 700r4 trans is rated at 350 ft lbs


http://www.5speedtransmissions.com/calculators.html

Gear comparisons for 700R4 vs. other GM Transmissions:
.............................1st.......2nd....3rd....4th
Power Glide..............1.76......1.0
TH350 .....................2.52.....1.52....1.0
TH400......................2.48.....1.48....1.0
700-R4/4L60..............3.06.....1.63....1.0.....70
200-R4.....................2.74.....1.57....1.0.....67
4L80E......................2.48.....1.48....1.0.....75


http://www.magneticlynx.com/carfor/transc.htm

THESE CALCULATORS COME CLOSE, and may be very useful, that question, of Which gears to go with comes up frequently.
(youll generally want to select a rear gear ratio that multiplied times your transmission first gear ratio falls in the 10:1-10.5:1 range, for performance cars used on the street, with tires in the 24"-28" tall range)reading thru this thread and sub linked info should help, and yes, knowing your engines power curve and tire size and transmission gearing can help a great deal in selecting the correct rear gear ratio, and the use of over drive ratios adds to the flexibility of the choices.
your obviously going to need to consider tire diameter, rear gear ratio and transmission gearing, generally your want the first gear in the transmission multiplied times the rear differential gear ratio to fall in the 10:1-10.5:1 range and cruise at a bit higher rpm that the torque converter stall speed in 1:1 gearing, if you have a over drive gear having a lock-up converter sure helps and a trans fluid cooler is almost mandatory if you have a high stall speed torque converter.
EXAMPLE
if your transmission has a 3.00 low first gear you would take the average of 10.25 and divide by 3 and find a 3.4 gear is close to ideal,
do the same calc with a 2.48:1 first gear and you get a 4.11 rear gear., you can easily calculate rpms at 70mph and top speed in over drive gear if you know the transmission, rear gear and tire diameter. from info in the links below


USE THE LINKED CALCULATORS
http://www.wallaceracing.com/gear-speed.php
http://www.race-cars.net/calculators/et_calculator.html
http://www.wallaceracing.com/calc-rgr.php
http://www.datsuns.com/Tech/whentoshift.htm
http://www.frontrange4x4.com/forums/sho ... nformation
http://www.carcraft.com/techarticles/cc ... to_01.html
http://purplesagetradingpost.com/sumner ... index.html
http://www.tciauto.com/tc/gear-ratios
http://www.5speeds.com/ratios.html
if its a street driven muscle car, youll generally want to select a rear gear ratio that lets the car go thru the lights at the end of the 1/4 mile without having reached the extreme upper rpm range, of your engines power band in top gear, yet allow you to be taking full advantage of the power curve available, yet still maintain a semi reasonable 70mph cruise rpm level,
as an example
lets assume your car has 27" tall tires and a 4l80e transmission, and your engines max efficient rpm is 6200rpm
now if you have a 4L80E auto transmission , it has Gear ratios:
1 2 3 4 R
2.48 1.48 1.00 0.75 2.07
you generally want a 10:1-10.5:1 first transmission gear to rear gear ratio, so if we divide 10.25 by 2.48 we get 4.13:1
if we look at 70 mph with a 0.75 cruise we get a couple calculators to work with,the choice you make here is rather dependent on the intended power band and possibly the converter stall speed
http://www.wallaceracing.com/calc-rgr.php
http://www.wallaceracing.com/gear-speed.php
lets say we look at that 4.13:1 ratio, a 4.30 and a 3.73:1,
gearray.png

index.php


HERES A VERY COMMON RESPONSE I SEE POSTED ABOUT A REAR GEAR SWAP RESULT,S ESPECIALLY WHEN USING AN OVER DRIVE TOP GEAR TRANSMISSION
" GRUMPY, I Installed the Richmond 3:54 gears for my Dana 36 from Summit Racing. The part number was RMG-4901431.
Good choice, the vette woke up and runs like a bat out of hell."

http://www.wallaceracing.com/gearcalc.php

http://www.wallaceracing.com/gear-speed.php

http://www.summitracing.com/parts/rmg-4901431
keep in mind the rear gear ratio you select depends on BOTH the tire diameter and type of transmission you run, over drive ratios tend to help.Also depends on what size rear tires you plan to use.
here just for grins is what DD2000 makes its wild guess at my current corvettes combo, RUNNING WITHOUT THE NITROUS,notice torque peaks before the hp peak, and I must shift at 6300rpm because its starting to drop off by that point in the power curve (AS I DESIGNED IT TOO)as the engine combos designed to run nitrous from 3500rpm-6000rpm, if required but thats rarely been necessary for brisk performance on the street
gearrangec.png

you should ideally select a cam , tire diam. converter stall speed and differential gearing that put the engine rpm range in your power curve about 90% of the time
my383com.jpg

heres the resulting power band, of my corvettes 383 with an extensively ported custom stealthram intake and other mods like ported trickflow twisted wedge heads, erson roller rockers and a crane 119661 roller cam, with a 3200 stall converter stall and shifting at about 6350rpm N/A
my383dcom.jpg

notice changing the stall speed and shift points , by about 1000rpm, on both ends of the power band on the identical engine , being used on the transmission allows you to access a great deal more power from the engine far faster , the drive train change can easily result in 30% plus more power reaching the rear wheels, but it also allows you to select a longer duration cam, and is usually further enhanced with a matching change in rear gear ratio, from lets say a stock 2.87:1-3.08:1 to a more power transfer friendly 3.54:1-4.11:1 rear gear.
If you look at the graph the first stock converter power ranges from about a low of near 175 hp to near 500 hp, average near 338hp
If you look at the graph the second aftermarket,higher stall converter power ranges from about a low of near 300 hp to near 475 hp, average near 388hp, close to 80% more initial and easily 50 more average HP, yes that a bit mis-leading because in reality you can,t use the more effective cam with the lower stall speed converter so in reality the difference is FAR GREATER once the matched components are used, as the power curve on the stock engine would much lower


my383dacom.jpg

Example:lets say you run a muncie 4 speed manual transmission, M20 (1:1 4th gear), 27" diameter tires, 4.11 rear gear, and 60 MPH means the engine is running at 3090 PRM. If the tires are 26" then it's at 3200 RPM. 25" goes to 3300. If you want to actually keep up with traffic at 70 MPH then the numbers are 3600, 3700, and 3870, respectively.

http://users.erols.com/srweiss/calcrpm.htm

viewtopic.php?f=71&t=4696&p=12731#p12731

http://garage.grumpysperformance.co...electing-a-torque-converter-stall-speed.1715/

powerband.png

in a drive train set up for max efficiency the converter stall speed , and rear gear ratio will match the engines power curve and will be set up to have the trans let the converter spin up and grab at the lower end of the power band, and too shift to match the upper end to the most effective part of the torque curves upper end (a )and the transmission shift point will be set up near the upper end of the torque curve but past the peak power (b) set up that way, the engine can transfer power during the vast majority of its operation at near peak torque levels, looking at this engines power curve charted above that would be about a 3200rpm stall speed and about a 6400 rpm shift rpm point
Another example: M20, 27" diameter tires, 3.31 rear gears, and 60 MPH has the engine spinning at near 2400 RPM's, at 70 MPH it's at 2890.
gearratioch.png


RPM-Calcs-1.jpg

RPM-Calcs-2.jpg

now if you have a 4L80E auto transmission , it has Gear ratios:
1 2 3 4 R
2.48 1.48 1.00 0.75 2.07
as a general rule youll want about a 10:1-10.5:1 ratio with the transmission rear gear multiplied so 10/2.48=4.03:1 rear gear ratio, but the over drive ratio drops the effective cruise rpm to .75, so what would be near 3900rpm with the 4 speed manual trans above drops to 2925rpm

two engines producing the same HP at different RPMs will, given appropriate matching gearing, produce EXACTLY the same torque and EXACTLY the same HP at the wheels - provided, of course, equal amounts are lost within the drive train.
and thats true, but in most cases, cars are geared to maximize mileage to some extent the big block tends to have a broader torque curve that comes in at lower rpm making the gearing far more effective, its not PEAK power that counts its AVERAGE POWER. in the useable RPM BAND.
I constantly see guys who want to build a small block that will make 500hp at 7500rpm, then gear the car so the engine spends 90% of its time in the 1500-5500 power band, then they as why the cars a dog.
gmtransgeart.png

automatic-transmission-pans-2.gif

keep in mind , that if you select the cars rear gear and transmission gearing , correctly that your engines power band should be easily accessed by the cars gearing and allow the car to operate most of the time in or near its peak torque curve.
If you have an automatic transmission your converter stall speed should allow near instant access to the lower rpm end of your most efficient torque band , and the car should shift gears allowing the rpms to drop back near the peak torque level for max acceleration, if you engine can potentially make power from lets say 3200rpm to lets say 6700rpm but your transmission shifts at 5600rpm , and your converter stall speed limits you to 2500rpm, your not going to benefit from that combos efficient use of the power your engine can potentially produce., match that same engine to a 3300rpm stall converter and a trans programed to shift at 6800rpm, and you'll see a noticeable improvement in efficient use of your power band

READ THRU THIS RELATED THREAD

viewtopic.php?f=71&t=1715

http://www.grimmjeeper.com/gears.html
Realistically youll want to think thru the entire combo of engine and transmission, gear ratios, tires sizes etc.
and keep in mind , that if the engine in front of the transmission and its rear gear ratio makes decent power , the ratio of gearing the car has will be of less concern, to your cars acceleration, potential.
yes you should ideally get as close to 10:1 with the first gear ratio x final differential ratio,as you can to maximize the potential ,but if you have built a well matched combo with decent compression (usually near 10:1 if your going to use pump octane gas)and as much displacement as you can easily afford (383-406 in most small blocks and 454-496 on most big blocks when your trying to keep costs down) youll have little trouble spinning the tires with minimal effort even with less than ideal gearing , many guys fail to match the cars gearing to the engines power band, but just as many fail to build a well thought thru combo with matched components.
RELATED THREADS
viewtopic.php?f=69&t=7722&p=26767&hilit=logical+plan#p26767

viewtopic.php?f=50&t=428

http://garage.grumpysperformance.co...hysics-of-racing-info-lots-of-good-stuff.373/

viewtopic.php?f=50&t=1249

viewtopic.php?f=69&t=519

viewtopic.php?f=69&t=9930

viewtopic.php?f=71&t=10690&p=46305#p46305

viewtopic.php?f=69&t=5123

http://www.offroaders.com/info/tech-cor ... ph-rpm.htm

http://garage.grumpysperformance.com/index.php?threads/matching-the-combo.11020/#post-48707

difratiox.png

gear-chart.gif

http://www.jekylhyderacing.com/HeightofTires.htm

http://vexer.com/automotive-tools/speed-rpm-calculator

http://www.angelfire.com/fl/procrastination/rear.html

http://www.frontrange4x4.com/forums/sho ... nformation

http://www.carcraft.com/techarticles/cc ... index.html

the main idea of matching the drive train gear ratios is to keep the engine in its intended power band during the vast majority of its operation.
if youve got a 2.87:1 rear gear you'll spend a great deal more time in the 1500rpm-4500rpm band than if you have a 3.73:1 rear gear ratio simply because the engine can accelerate faster thru its power curve with the 3.73:1 rear gears.
It should be obvious that knowing the engines effective torque curve will be critical, and keep in mind that horsepower (THE ABILITY OF THE ENGINE TO DO WORK) goes up as the AVERAGE rpm band goes up if the torque remains constant or even similar.
you would ideally like the transmissions first gear ratio multiplied by your cars rear gear ratio to fall in the 10:1-10.5:1 ratio, and have a tire diameter that allows the car to cruise in the range between your engines stall and peak torque but much closer to stall speed.On most street performance cars the stall speed falls in the 2600rpm-3200rpm range and ideally the cruise speed at about 70 mph should fall a couple hundred rpm higher that the cars stall speed.there's several calculator links posted lower in the thread, to help you to figure it out

OBVIOUSLY theres a huge range of potential SBC builds possible and you'll want to select one that best fits your goals, If your intent on building a race 383-406 on a semi limited budget, for a light car Id at least look at these parts, installed on about a 10.5:1 compression short block, with a manual transmission and a 3.73:1-3.90:1 rear gear and 26'-28" slicks, some full length 1 3/4" headers and 1.6:1 ratio roller rockers,and a good 850 cfm holley carb, while that would not be my choice for a car designed for street use where you need some low and mid range, it would certainly produce good peak power

OBVIOUSLY KNOWING YOUR TIRE HEIGHT HELPS IN CALCULATIONS
Tire_markings_sm.gif

http://www.brodix.com/heads/ik210dyno.php

http://www.summitracing.com/expertadvic ... calculator

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=5078

http://forum.grumpysperformance.com/viewtopic.php?f=69&t=3814

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=181

http://www.quickperformance.com/Suspens ... ep_44.html

you will find these threads useful if you read thru and look thru sub links most people don,t take the time to research and plan their engine builds to match the application, and as a result they tend to think they all want 500-600 plus hp from reading the magazine articles , but the truth is that a responsive engine with massive torque in the useable rpm range make for a far better choice if the cars street driven, now thats not saying you can,t have both impressive horsepower and a great torque curve but just keep in mind every choice is a compromise and if you concentrate on building an engine that works in the rpm band you actually use rather than getting mesmerized by peak hp numbers alone youll have better results youll also need to keep in mind it does no good to build a killer engine that produces 500-700 plus hp at 6700rpm and match it to a rear gear ratio and transmission gearing, and shift points or converter stall speed, that keeps the engine in the 1600rpm-6000rpm power range 90% of the time, if your smart your not competing for peak hp bragging rights your trying to build , impressive and instantly responsive torque in the useable rpm band, you also want to remember DURABILITY trumps PEAK POWER, you can,t win in the long term if the cars constantly needing repair and replacement of parts

AS A GENERAL RULE, a good compromise on a street strip cars gearing, will be found if youll match the transmission first gear multiplied by the rear gear ratio, to fall in the 10:1-10.8:1 range
as a rough guide
if the tire height is under about 28"
rear gear ratio x first gear ratio should be close to 10:1
if the tire height is over about 28"
rear gear ratio x first gear ratio should be close to 11:1 and match the tire size/diam. on the car, and rear gear ratio in top gear or OVER DRIVE to allow the car to cruise in the 2300rpm-2800rpm at 70 mph range...find the best compromise that gets as close to both as you can

read this

viewtopic.php?f=44&t=1010&p=1829&hilit=+horsepower#p1829

Duration_v_RPM-Range_wIntakeManifold01.jpg


tirespeed.jpg

tirespeed1.jpg


TireSpeedRatings01.jpg


http://www.datsuns.com/Tech/torquehp.htm

http://www.coastdriveline.com/htmlfolde ... ator2.html

viewtopic.php?f=44&t=1010&p=1829#p1829

viewtopic.php?f=71&t=741

http://www.prosystemsracing.com/calculate.html

That answer depends on the fuel octane, cylinder head temp. and several other variables but generally 8.0-8.5:1 dynamic works out well if your going to run mid grade pump gas

0311phr_compress_07_z.jpg


READ THIS THREAD!
http://www.chevytalk.org/fusionbb/showt ... tid/92966/


http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

HERES OTHER INFO LINKS

http://www.wallaceracing.com/reargear.htm

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://users.erols.com/srweiss/transc.htm#tabtop

http://users.erols.com/srweiss/transc.htm#Auto
heres some different calculators

http://www.kb-silvolite.com/calc.php?action=comp2

http://www.wallaceracing.com/dynamic-cr.php

http://www.smokemup.com/auto_math/compression_ratio.php

http://drag-zone.com/calculators.html#6

viewtopic.php?f=55&t=6546&p=20829#p20829

http://not2fast.wryday.com/turbo/compre ... sure.shtml
average the results
http://www.geocities.com/z_design_studi ... zx_tt.html

gear spread sheet that comes in handy THANKS TO 1FATGMC

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

HERES OTHER INFO LINKS

http://www.datsuns.com/Tech/whentoshift.htm

http://www.wallaceracing.com/reargear.htm

http://www.converter.com/vigilante.htm

http://transmissioncenter.net/4L80E.htm ... 7AodDjIACQ

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://www.gearvendors.com/hrgmratios.html

http://www.hotrod.com/how-to/transmissi ... axle-swap/

http://users.erols.com/srweiss/transc.htm#tabtop

http://users.erols.com/srweiss/transc.htm#Auto

http://www.thirdgen.org/calculations

http://www.corvetteactioncenter.com/tec ... scalc.html

viewtopic.php?f=32&t=430

IDEALLY you would sellect the horsepower goal, and the displacement,youll work with too reach that goal. then the cylinder heads, intake and exhaust are sellected that supply the necessary flow rates,in that rpm band, you pick the cam too match the intended rpm band,and flow rates and power range for the application, you then match the compression ratio, to the cam timing too maintain the correct dynamic compression ratio, and you sellect the matching drive train and gearing to keep the engine IN the matched rpm band the vast majority of the time.
naturally if your limited to a set displacement or compression ratio the other factors must be sellected with those limits in mind

30228b.gif

IM reasonably sure this charts based on a 350-383 chevy or similar size engine, but its a good rought guide on most engines under 400cid displacement on matching the duration to the intended operational rpm band

In most cases the upper rpm band limit is either limited by valve float with the more common hydraulic lifters, or the auto transmissions shift rpm point,(yes there adjustable in some cases but rarely shift higher than 5500rpm-6000rpm even with a shift kit installed) theres not much point in designing a combo that runs into potentially higher rpms if you'll seldom reach, or can,t reach them., the lower rpm limits set by the necessary minimum lower rpm band the cam and compression ratio , and engine displacement will allow the engine to smoothly produce power from.
most performance cams list a MINIMUM converter rpm or cruise rpm



" GRUMPY?? I plan on adding a mild cam into the mix on my TPI corvette?.

whats the ideal power range in the TPI? "



a 2800rpm-3000rpm stall converter and ideally a 3.54:1-3.73:1 rear gear really wake up even a stock tpi corvette engine, but become almost mandatory when you upgrade the cam.
the stock TPI starts to get restrictive at about 4500rpm with the stock cam, by about 5500rpm its pretty much a lost cause UNLESS you do a bit of porting, add a better cam and ideally better cylinder heads, theres a nearly endless list of improvements that can be made, but to get the power efficiently to the pavement it helps top have the engine spend most of its time in the 3500rpm-5000rpm power band, thats what the higher stall converter, and rear gearing do.
trust me ask around to those guys who have done it, adding a 2800rpm-3000rpm stall converter and ideally a 3.54:1-3.73:1 rear gear really make the car come alive!
yes it helps even more if you install a better set of heads a better intake etc, but its the gears and converter allow you to stay in the engines sweet part of the power band
if you look around youll find guys that forgot that, fact, and concentrated totally on engine upgrades, they eventually find that the car just never responds correctly or they eventually learn and get the drive train matching the engines power curve.

heres your trans gears

2.74 1.57 1.00 0.67

rear gear 3.55:1

tires 27" tall


all the info you need to calculate gear ratios, speeds and engine rpms is here, or in the sub linked info


http://www.geocities.com/z_design_studi ... zx_tt.html

viewtopic.php?f=71&t=555




lets look at your particular

plug in your specs to the calculator and links, and look nup your cam specs for the suggested cruise or operational rpm band

heres free cam selection software

http://www.compcams.com/Camquest/default.asp

btw once you use it to find that approximate lift ,duration and lca, you can buy any companies cams with similar specs.

BTW HINT, with that rear gear and compression ratio , ID STRONGLY SUGGEST YOU stay UNDER 218-220 duration at .050 lift and with a 108-112 LCA

Most auto transmissions are either adjustable,OR PROGRAMMABLE in some cases, or there are aftermarket shift kits available too alter the shift points or convert to manual operation, but in most cases you'll still find 5500rpm-6000rpm about the max possible shift point, and frequently you can,t get quite that high with the less expensive kits.
for a street car the shift points are lower so the cam selected should be milder to match the realistic rpm band that's actually in use!

http://store.summitracing.com/egnsearch ... &y=13&x=26

http://www.jegs.com/webapp/wcs/stores/s ... 9_-1_10529
 
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we've all made mistakes its how most of us learn, at times, I spent several hours when I was 18 years old replacing a pressure plate and clutch disk in my 1967 firebird Id just installed a 455 Pontiac stroker engine in, unfortunately I managed to have the wrong side face the fly wheel, face the clutch pressure plate, so the clutch would not function, I had to pull it all back out, flip the disc and reassemble, converting what is normally a 2-3 hour job into a 5-6 hour job.
then, I absolutely cooked the clutch because the disc Id purchased was not top quality, and the pressure plate was a stock diaphragm style not suited to race use, like the 3800 lb borg and beck that I replaced it with, (not knowing the difference at that time, cost me a good deal of time and cash doing something over that I should have researched nd done correctly the first time, but hey I was 18 and knew everything at that time!) so I had to repeat the job with-in weeks but it was a huge learning experience and I learned a great deal about how things worked, what parts to buy and how to check out things along with a great deal more info, like large sticky slicks and a high torque 455 Pontiac engine (stroker crank this was before the factory 455) with a 4 speed and a 3.36:1 rear gear are not the ideal combo for long clutch life.
the 3800 lb borg and beck pressure plate, Zoom disc, lake wood bell housing, hays flywheel, and 4.11:1 rear gears that I replaced it with,lasted several years until I eventually sold the car.
Gears, Mph, And Tire Height,
its all a learning process, you want too simply want to mentally take a step back, take a deep breath or two,
and start testing to find out whats working correctly,in your current combo,
whats not working up to your expectations,and if its not meeting your goals, logically calculate what should change,
and then calculate what can be adjusted or if necessary parts that can be logically replaced, and re-tested,
if that required too improve the performance.
don,t make the all too common mistake of thinking adding horsepower is the only route to improved performance.
suspension mods, better shocks, better brakes, a stiffer frame, larger diameter and wider tires, and drive train gearing and removing weight,
and correctly setting up the cars chassis to more effectively apply weight transfer ratios,
swapping to lower weight parts,or stronger , or more durable parts, use of stronger drive train components, better matched gear ratios, all help


After you've figured out how fast you want to go, you need to find the weight of the car and determine how much horsepower you'll need to accomplish your goal. The formula to estimate amount of horsepower for a terminal mph in the quarter-mile is: hp = (mph / 234)3 x weight. As an example, if your car weighs 3,000 pounds, you'll need about 500 hp to run 130 mph, and if your car weighs 4,000 pounds, you'll need about 685. This is simply a power-to-weight calculation, and experience has shown us it is a little conservative, much depends on the engines torque potential. There are a lot more factors involved in goin' fast, but this is a good place to start, and it shows why weighing less is better.

The next thing you need to do is find out where your engine will make peak horsepower and pick a rear gear that will put the engine at about 200 rpm above that number going through the traps in High gear. Here is the math: gear ratio = (rpm x tire diameter) / (mph x 336). This is closely tied to the size of the tire you are going to run, so before picking a rear gear ratio, find the largest tires that will fit under the rear. You should also note that an automatic transmission in High gear will exhibit about 5 percent slippage, so you will need to add that to equation.

Even a correctly rebuilt TH350 or 200r4 should easily handle a t-bucket or light weight car,due to the light weight, but as car weight is increased the stress levels and heat increase also. , but a good trans cooler is mandatory on a high stall converter equipped transmission, for durability.
I would point out that a well built TH400 or a 4L80E IS STRONGER than a similar TH350 so even if you go with a stock trans Id go with the TH400,or 4L80E, it weights a bit more and will absorb a bit more power but durability is more important in the long run than a couple hundredths of a second in et.especially in a light weight car that should have little problem scaring the hell out of you if properly built!


viewtopic.php?f=45&t=437

viewtopic.php?f=71&t=447

viewtopic.php?f=33&t=769

viewtopic.php?f=44&t=362&p=2778&hilit=pontiac+info#p2778[

viewtopic.php?f=44&t=450&p=554&hilit=pontiac+info#p554

http://www.superchevy.com/how-to/tr...g-the-ultimate-4l60e-with-better-gear-ratios/

http://garage.grumpysperformance.com/index.php?threads/select-a-gear-ratio-or-trans-or-both.10493/

viewtopic.php?f=44&t=368&p=450&hilit=pontiac+info#p450

http://bmracing.com/wp-bnmcont/uploads/117101.pdf

http://www.phoenixtrans.com/html/gmtrans.html

the links above are worth reading thru

I got EMAILED asking how and why swaping gear ratios works and why if your using the same engine does it even matter?

well, thats a reasonable question if your not up on the basics of how it works so Ill try and explain it in basic terms
first you need to under stand that the rear gear ratio and the transmission work as a combined team to provide the transfer of rotary force from the engine to the pavement.

first you need to understand that horsepower is simply a mathematical way to express the RATE at which TORQUE is available and applied
and torque is basically the force in the cylinders thats trannsfered to the crankshaft thru the connecting rods and the leverage in the cranks throw TIMES the NUMBER of POWER STROKES PER SECOND and that the current design of auto engines make thier best power over a narrow rpm range, usually in the 4000-6000rpm range, below that rpm range theres just not quite as effective of cylinder filling and torque is still building, since theres less power strokes per second theres less total torque,and above the engines power band,efficiency falls off rapidly after the 4000rpm-6000rpm zone,(depends on components used)
so the KEY is both KEEPING the engine IN that effective torque production range and having the most power strokes applied to the pavement thru the drive train.

example
a 3.07 rear gear allows the engine to spin 3.07 times in direct drive or top gear in a NON-OVERDRIVE type trans
but in first gear,which could have a 2.52 first gear ratio like a TH 350

http://www.oldengine.org/unfaq/leadfoot/trans.htm

we see it has a 2.52 too 1 ratio in first gear
with that 3.07 rear gear we effectively have a 7.74 :1 ratio so if the tires turn over once the engine has spun over and applied approximately 7.75 times in low gear,swap to a 4.11 rear and youve just increased the number of power strokes applied to 10.35 timesor 34% more torque avalible at the rear wheels, from the same engine
the down side is that the engine runs above its effective rpm range at a lower top speed and gets less efficient mileage

http://users.erols.com/dmapes/GEARCLC.HTM


http://users.erols.com/srweiss/calcmph.htm

below is a closely related post/thread

we have all heard it, " you need massive low rpm tq" "you need a screaming high rpm hp peak" well heres some info,
More in-depth description:
http://www.revsearch.com/dynamometer/torque_vs_horsepower.html
http://www.dynacam.com/Product/Torque_vs__Horsepower/torque_vs__horsepower.html
http://vettenet.org/torquehp.html
http://auto.howstuffworks.com/horsepower4.htm
http://homepage.mac.com/dgiessel/engine/hpvstq.html

first thing to keep in mind is that theres no such "thing" as horsepower, horsepower is a mathmatical formula for the RATE at which TORQUE can be applied the formula for hp is (tq x rpm/5252=hp
example
450 ft lbs of torque at 3000rpm=257hp
450 ft lbs of torque at 6000rpm=514hp
because the torque at the higher rpm useing gearing can be applied faster
here read this

http://www.69mustang.com/hp_torque.htm

http://www.ubermensch.org/Cars/Technical/hp-tq/

http://vette.ohioracing.com/hp.html

where most guys go wrong is in not correctly matching the cars stall speed and gearing to the cars tq curve, if you mod the engine for increased high rpm performance but fail to also match the stall speed and gearing to that higher rpm tq curve much of the potential improvement is wasted.
example

chart8.gif

in the close to stock engine above, the engine should be geared to stay in the 3500rpm-5000rpm range for max acceleration (lower in the rpm range if mileage is a big factor)
chart2.gif

in the moded engine above the rpm range moved to 4000rpm-6500rpm requireing differant rear gears and slightly higher stall speeds to gain max acceleration in the same car,
you should readily see that a trans that shifts at 5000rpm will work in the first example but would waste most of the power curve in the second example,where shifting at 6500rpm under full power acelleration would make more sence.
a 3.08 rear gear and 700r4 trans matches the first example well but it would take a swap to a 3.73-4.11 gear to allow the engine in the second example to keep its most effective power band matching that second power curve well.

links youll need to figure out correct rear gear ratios

http://www.miata.net/garage/tirecalc.html

http://www.wallaceracing.com/reargear.htm

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://www.prestage.com/Car+Math/Ge...io/default.aspx

http://www.geocities.com/z28esser/speed.html

http://server3003.freeyellow.com/gparts/speedo.htm

http://www.pontiacracing.net/trannyratios.htm

http://www.tciauto.com/tech_info/gear_ratios.htm

yes I,m only too well aware most of those reading the thread will never bother to read the links and sub-links but its your lost opportunity, to learn a great deal if you do ignore the linked info
http://www.bgsoflex.com/crchange.html

http://www.hotrod.com/techarticles/hrdp ... ewall.html

http://www.race-cars.net/calculators/co ... lator.html
http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

HERES OTHER INFO LINKS

http://www.wallaceracing.com/reargear.htm

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://users.erols.com/srweiss/transc.htm#tabtop

http://users.erols.com/srweiss/transc.htm#Auto
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php

http://www.epi-eng.com/piston_engine_te ... torque.htm
gmtransgeart.png

POWER (the rate of doing WORK) is dependent on TORQUE and RPM.
TORQUE and RPM are the MEASURED quantities of engine output.
POWER is CALCULATED from torque and RPM, by the following equation:

HP = Torque x RPM ÷ 5252
epg1.gif

Figure 3

Note that, with a torque peak of 587 lb-ft at 3000 RPM, the pink power line peaks at about 375 HP between 3500 and 3750 RPM. With the same torque curve moved to the right by 1500 RPM (black, 587 lb-ft torque peak at 4500 RPM), the peak power jumps to about 535 HP at 5000 RPM. Again, moving the same torque curve to the right another 1500 RPM (blue, 587 lb-ft torque peak at 6000 RPM) causes the power to peak at about 696 HP at 6500 RPM

Using the black curves as an example, note that the engine produces 500 HP at both 4500 and 5400 RPM, which means the engine can do the same amount of work per unit time (power) at 4500 as it can at 5400. HOWEVER, it will burn less fuel to produce 450 HP at 4500 RPM than at 5400 RPM, because the parasitic power losses (power consumed to turn the crankshaft, reciprocating components, valvetrain) increases as the square of the crankshaft speed.

The RPM band within which the engine produces its peak torque is limited. You can tailor an engine to have a high peak torque with a very narrow band, or a lower peak torque value over a wider band. Those characteristics are usually dictated by the parameters of the application for which the engine is intended.

An example of that is shown in Figure 4 below. It is the same as the graph in Figure 3 (above), EXCEPT, the blue torque curve has been altered (as shown by the green line) so that it doesn't drop off as quickly. Note how that causes the green power line to increase well beyond the torque peak. That sort of a change to the torque curve can be achieved by altering various key components, including (but not limited to) cam lobe profiles, cam lobe separation, intake and/or exhaust runner length, intake and/or exhaust runner cross section. Alterations intended to broaden the torque peak will inevitable reduce the peak torque value, but the desirability of a given change is determined by the application.

ept2.gif


https://robrobinette.com/et.htm

http://www.cprparts.com/HPcalculator.html

https://www.gregraven.org/hotwater/calculators/qm-from-wt-hp.html

https://www.tciauto.com/racing-calculators

https://teamcsr.net/Racing Calculator.htm

https://racingcalcs.com/horsepower-hp-required-for-elapsed-time-et-goal-calculator/

calculators like those linked above assume you have close to ideal,
traction
(suspension, tires, weight transfer)
and gearing
( transmission gearing, stall speed and shift between gears effectively in the ideal power band)
to maximize the cars acceleration potential
 
Last edited by a moderator:
BTW the factory 700r4 that comes in some corvettes is designed for about 350 ft lbs of tq, it can be strengthened, but its not and never will have the strength of the 4L80E. or TH400.
the factory 700r4 should work for quite awhile if your trans fluid temps are kept under about 210F MAX, its HEAT more than TORQUE that kills transmissions when were talking about mildly modified engines, the transmissions designed to work with 350ft lbs according to G.M. but theres thousands of them working at the 400 ft lb levels, remember only your PEAK hp/tq levels will even come close to exceeding the design limits.
I generally suggest upgrade if your exceeding 450-500 ft lbs regularly, as that level tends to cause problems after a short time if your also subjecting the trans to shock loads like hard launches
while thats good info and theres no doubt that the stock 700r4 can be improved with aftermarket components, if your building a 500hp sbc based engine beefing up the stock trans makes a great deal of sense.but your basically beating a dead horse if your using a 700r4 with an engine that exceeds about 600 ft lbs of torque,at 500 plus hp,its torque loads and heat, not horse power that kills a transmission, youll be far ahead swapping to a 4L80E or a manual shift version if you build a serious engine
the required stall has little to do with the type of lifter your using, its need, to be used, or changed is determined by the rpm range of the cam you select and your car weight,the cars automatic transmission first gear ratio, tire diameter and rear gear ratio.
a mild roller cam would work with a stock stall converter just as a mild flat tappet lifter cam will.
the whole idea of swapping to a higher stall speed torque converter is to allow the engine UNDER LOAD to jump in rpm up into the engines most efficient power range or the most effective part of the torque curve.
craneq2.gif

Duration_v_RPM-Range_wIntakeManifold01.jpg


http://garage.grumpysperformance.co...electing-a-torque-converter-stall-speed.1715/


http://garage.grumpysperformance.co...hing-the-drive-train-to-the-engine-combo.741/

http://garage.grumpysperformance.co...electing-a-torque-converter-stall-speed.1715/

http://garage.grumpysperformance.com/index.php?threads/more-converter-stall-speed.12964/

http://garage.grumpysperformance.co...mbers-or-a-good-street-combo-your-after.5078/

http://garage.grumpysperformance.co...d-high-spring-pressures-don-t-work-well.1489/

http://garage.grumpysperformance.com/index.php?threads/matching-parts-and-a-logical-plan.7722/

http://garage.grumpysperformance.co...gine-to-match-the-cam-specs.11764/#post-55651
one factor thats frequently over looked is the oil feed and return line internal size and line heat rating,THINK IT THRU, now it should be obvious that fittings tend to have smaller more restrictive holes thru them than the hose internal dimensions of the fittings used with that hose, a fitting designed for 3/8" hose wont allow full 3/8"hose or component oil flow rates, AN-6 is normally considered about equal to 3/8" but thats doesn,t tend to be true, AN-8 size fittings are usually used to get decent flow in a 3/8" oil cooler , if your oil cooler has 3/8" internal passages youll want an AN#8 line size too insure the MINIMUM 3/8" internal passage size is maintained , and you really NEED a full 1/2" or AN#10 size fittings and internal fluid transmission cooler lines to a fan cooled trans fluid cooler rated at at least a 24000 lb vehicle weight for race /performance use, and not restricted by use of the internal passage size of AN#6 fittings which are at best minimal and only delay the heat build-up related problems.
oilcoolq3.jpg

http://www.summitracing.com/parts/prm-13182

If I did it again Id select this trans cooler (pictured below) as the larger line size would help reduce flow restriction, its smaller width would make it easier to install,
THATS IMPORTANT!, MEASURE VERY CAREFULLY BEFORE ORDERING
I know several people that ordered trans coolers and found they would not fit into the originally intended location because they failed to correctly measure the intended location space, in ALL three dimensions,and over the whole space, before ordering , I know I failed to measure carefully so I was forced to place it where the spare tires normally mounted

http://www.summitracing.com/parts/FLD-DB30901/?rtype=10
Fluidyne High Performance DB30901 - Fluidyne Oil Cooler with Fan Kits

fld-db30901_w.jpg


READ THE LINKS AND SUB LINKS
http://garage.grumpysperformance.co...late-gear-ratios-and-when-to-shift-calcs.555/
gmtransgeart.png

do a few calculations, think about the rpm band
YOUR engine makes its best power in,
and YOUR tire diameter
and YOUR cars weight
and YOUR rear gearing,
and YOUR trans GEARING
as a general rule if your looking for brisk street performance,
(especially with an over drive transmission)
youll want the transmission first gear . multiplied times the rear gear ratio to fall in the 10:1-10.6:1 range
and youll want the engine to cruse at 70 mph in the lower end of the engines effective torque curve, If you take the time and effort to do all the math and accurately match the rear differential gear ratio, transmission gearing and tire diameter youll eventually find a clear consistent advantage to use of a transmission with an over drive top gear ratio of near .70-.75 in most cars and a rear gear ratio in the 3.73:1-4.11:1 range for performance cars.

http://garage.grumpysperformance.co...late-gear-ratios-and-when-to-shift-calcs.555/

http://www.wallaceracing.com/gear-speed.php

http://vexer.com/automotive-tools/speed-rpm-calculator

https://www.summitracing.com/expertadviceandnews/calcsandtools/gear-ratio-calculator

http://spicerparts.com/calculators/transmission-ratio-rpm-calculator

http://www.differentials.com/technical-help/differential-gear-ratio-calculator

http://vexer.com/automotive-tools/1-4-mile-ET-HP-MPH-calculator
you know its great feeling to find your dealing with someone who actually takes the effort to read links and understand the basic concepts posted!
Ive been trying to point out stuff like that for 40 years and you might be absolutely amazed but Id bet 90% of the guys looking at those two graphs , would instantly pick choice (B) based on only seeing the higher peak numbers alone and in about 90% of the cases (A) would make the better choice for an engine designed for street use and Id bet a great deal of money 99% of the readers would bother to actually compare the two graphs point vs point.

Id also point out that a good street/ strip engine combo tends to have torque numbers peak at roughly the same levels (with-in about 15%) as the hp does and with at least 1000rpm or greater between the peaks and all after 3500rpm and before 6500rpm , thats assuming the rear gearing and converter stall match the engines effective power band of course .
when the two peaks occur earlier in the rpm band you tend to need to constantly shift gears, when it hangs on above 6500rpm you tend to develop long term valve train durability issues..

EXAMPLE

114681q.jpg

something like this would normally result it a fun street combo in your average muscle car with a 3.54:1-3.90:1 rear gear a 4 speed and 26"-28" tires, having an over drive trans is also a big help.

383mildtpi.jpg

in the same car something like this would drive you crazy constantly needing to shift gears, its designed for an auto trans an 2.57:1-3.07:1 rear gears

sbcrollerdy.jpg

something like this in the same car would be miserable to drive on the street, and your sure to be having valve train durability issues eventually if you put a great deal of street time on an engine set up like this
these threads should provide you with a great deal of differential related info

viewtopic.php?f=45&t=166&p=1875#p1875

viewtopic.php?f=45&t=273

http://garage.grumpysperformance.co...electing-a-torque-converter-stall-speed.1715/

viewtopic.php?f=45&t=757

viewtopic.php?f=71&t=1261

viewtopic.php?f=71&t=945
 
Last edited by a moderator:
anyone tried swapping to a 6 speed auto yet?

here the new heavy duty 6 speed automatic transmissions

Type: six speed RWD / AWD, electronically controlled automatic overdrive transmission with torque converter clutch. Clutch-to-clutch architecture, with integral Electro / Hydraulic Controls Module.

Engine Range: 6.6L

Max Gearbox Torque: 885 lb.-ft.

Weight: 240 lbs.

Assembly Site: Ypsilanti, MI

Applications: Chevrolet Suburban, Chevrolet Silverado HD, GMC Yukon, GMC Sierra HD
6l90.jpg



Type: Six speed rear-wheel-drive, electronically controlled, automatic overdrive transmission with torque converter clutch. Clutch-to-clutch architecture with integral electro/hydraulic control module

Engine Range: 4.4L-6.2L
Max Gearbox Torque: 664 lb.-ft.

Weight: 225 lbs.

Assembly Site: Ypsilanti, Michigan

Applications: Cadillac STS-V, XLR-V, Escalade; Chevrolet Corvette; GMC Yukon

6l80.jpg


information confirming that the 6L80 is a "conventional" planetary gearset, torque converter equipped transmission

The 6L80 has "clutch to clutch" shifting except for the 1-2 shift. Thi.s means that only first gear has a sprag or one way clutch. I assume the intent of this is to eliminate the drag of the one way clutch. It also means more sophistication required to control the clutches

.


Here's a few excerpts from a document I found titled 09_6L80_MYC_n.doc

(Quote)
While the basic aluminum housing for 6L80 transmissions can remain identical for a wide variety of applications, including front- and rear-mounting, car and truck applications, and rear- or four-wheel-drive applications, the case extensions and bell housings can be modified for nearly any longitudinal drivetrain vehicle. The modular concept of the new Hydra-Matic 6L80 six-speed automatic centers on the desire for common components and manufacturing tooling for four different size variants of the new 6-speed family. The main case uses three main components, and those components are the same for all variants of the transmission. For the first applications of the new transmission, the 6L80-E contains three gearsets, a conventional input planetary gearset with four pinion gears. There is one compound output gearset and one simple output gearset. The compound output gearset uses three sets of pinion gear pairs, with one set of pinions meshing with the sun gear and the other set with the ring gear. This arrangement allows for optimal ratio steps with a 6.04 overall ratio spread.

There are two torque converter sizes, 258mm and 300mm. The 258mm applications use a twin-plate torque converter lockup clutch, while the 300mm applications use a single-plate torque converter lock-up clutch. Both types of clutches make use of GM’s proprietary electronic controlled capacity clutch (ECCC) technology, which uses a small, regulated amount of slip to dampen out engine pulses. This creates a smoother running drivetrain, especially during shift events.


A wide overall ratio spread of 6.04:1 allows a “steep” first gear, as well as very “tall” overdrive top gear for low-rpm highway cruising. Acceleration is maximized, as is fuel economy. Engine noise is also lower during cruising. Both fifth and sixth gears are “overdrive” gears, for example.

Gear changes from second to sixth gears are accomplished with clutch-to-clutch control, where an oncoming clutch is engaged and an “offgoing” clutch is released in a precise manner to achieve the ratio change. The first-to-second upshift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds. The clutch-to-clutch shifting and single freewheeler allows significant reductions in packaging requirements and, as a result, the new six-speed is nearly identical in size to the four-speed transmission it replaces.

A wide overall ratio spread of 6.04:1 allows a “steep” first gear, as well as very “tall” overdrive top gear for low-rpm highway cruising. Acceleration is maximized, as is fuel economy. Engine noise is also lower during cruising. Both fifth and sixth gears are “overdrive” gears, for example.

Gear changes from second to sixth gears are accomplished with clutch-to-clutch control, where an oncoming clutch is engaged and an “offgoing” clutch is released in a precise manner to achieve the ratio change. The first-to-second upshift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds. The clutch-to-clutch shifting and single freewheeler allows significant reductions in packaging requirements and, as a result, the new six-speed is nearly identical in size to the four-speed transmission it replaces.


The Hydra-Matic 6L80 is produced in Ypsilanti, Michigan.
(End Quote)
 
HEY GRUMPYVETTE, my th350 is on its last legs and I want to upgrade to an over drive transmission, I can get a 700r4 or 200r4 for about the same price, whats a better transmission?



this debate on the difference in strength between the rebuilt 200r4 and 700r4 has gone on for years, both transmissions have guys that say they can build them to handle outrageous power levels , but the evidence I see it that the well built 200r transmissions seem to hold up longer once you start hitting them with over 500-600 ft lbs of torque on a regular basis. and neither of the transmissions can equal the heavier built 4l80e once you start using that power level on the drive train.
both the 700 and 200 transmissions were factory designed for under 400 ft lbs of torque
the 200r4 has a better gear split
TH350 2.52 1.52 1.00 --- 1.94
TH400 2.48 1.48 1.00 --- 2.07
TH200-4R 2.74 1.57 1.00 0.67 2.06
TH700-R4 3.06 1.62 1.00 0.70 2.29
4L80E 2.43 1.49 1.00 0.75 2.07

or put a different way, Ive seen a lot more 700r4 transmissions that failed than the 200r4s but they both lack the strength and parts mass/size of the 4l80e, but that also posses a problem in that the 4l80e is larger and heavier and more difficult to fit in a trans tunnel and can require a expensive control module, so you might want to think thru your goals, and cost if your swapping transmissions to hold a significantly more powerful engine swap in your car, as its rather foolish to need to go thru the process TWICE or THREE times in a quest to find a transmission that won,t grenade on you once you start beating on it!
but be aware that ALL performance transmissions wear due to torque loads, impact loads and heat levels, so a large transmission cooler is your first defense against ANY transmission problems



RELATED INFO

http://www.cbtransmission.com/page/page/5480419.htm

http://www.ckperformance.com/resources/ ... NENTS.html

viewtopic.php?f=39&t=3094&p=12845&hilit=4l80e#p12845

viewtopic.php?f=57&t=176

http://www.nyracer.com/trannygear.htm

viewtopic.php?f=87&t=10429
 
BTW I recently advised a guy on his engine combo,suggesting both engine and drive train components but suggested he do the drive train mods FIRST as they would make a huge improvement in the cars drive-ability once the new engine components were installed, I suggested a 3000rpm stall converter and strongly suggested he swap from a 2.87:1 rear gear to a 3.73:1 rear gear in his 1986 corvette
well as unlikely as it is most times, he actually followed that advice and installed the 3.73:1 rear gear and 3000rpm stall converter, heres what he had to say after just those components were changed with no engine mods yet done!


"I just thought I'd let you know how much of a difference there is in the feel of my corvette after swapping to the 3.73:1 gear ratio . I usually drive my car only around town, short trips like to the store, and rarely get on the interstates where I have to run 55 - 70 mph ,so the change was great, but My stock TPI engine seems to have gained a great deal more power, and the cars much more fun to drive, I was worried about the 3000 stall, but your correct, its not that bad if you drive like a sane person and only really allows the car to rev a great deal higher than stock if I floor it, yes theres some obviously higher converter slip but nothing drastic..
Between the higher stall converter speed and rear gears, The motor really revs up much faster now, and under WOT and breaks the tires loose on the 1-2 shift and 2-3 leaving two long black tire marks that are about 4 1/2 car lengths on the 1-2 shift and 2 car lengths on the 2-3 shift before the changes it barely spun the tires in first and only chirped them on the 2-3 shift"


the difference is in both the available power transmitted to the rear wheels and where in the power curve the engine starts to deliver that torque to the drive train


gs039_dyno.jpg

heres an example of a mildly modified TPI dyno, now it should be rather obvious that
if you apply the engine torque starting at about 2000rpm with a stock converter , you start out with about 260 ft lbs multiplied by a 2.87 rear gear you have about 745 ft lbs at the rear wheels
if you just start by flooring the car from a standing start
, but with a 3000rpm stall converter and a 3.73 rear gear that jumps to a useable 290ft pounds times a 3.73:1 rear gear to about 1081ft lbs at the rear wheels even with a mild nearly stock engine.....now with the correct cam, a better intake and heads, that moves the whole power curve higher and further up the rpm band the difference can be far more impressive, if you measure average power at the rear wheels, that nearly instant 335 ft lb advantage matters


related info
http://www.circletrack.com/enginetech/c ... index.html

http://www.revsearch.com/dynamometer/to ... power.html

http://www.epi-eng.com/piston_engine_te ... torque.htm



Knowing how much torque you are applying (this assumes you have perfect traction with only a 10% slippage at your slick) to the axel here is a chart of aftermarket axels listing their failure points (on average).



28 spline axel________1.200" dia. ________ 4,571 lbs.-ft. stock (GM test data)
28 spline axel stub ___1.250" dia. ________ 3,787 lbs.-ft. stock Corvette (Dana 44)
30 spline axel________1.250" dia. ________ 6,473 lbs.-ft. stock (GM test data)
31 spline axel________1.315" dia. ________ 7,000 lbs.-ft. (Ford 8.8" rear)
33 spline axel________1.370" dia. ________ 8,200 lbs.-ft. (GM 14 bolt truck)
35 spline axel________1.500" dia. _______ 9,600 lbs.-ft. (Dana 60)
40 spline axel________1.710" dia. _______ 12,000 lbs.-ft.

Here is a web site with a great graphic that shows why spline count is so important.
http://performanceunlimited.com/documen ... guide.html
 
http://purplesagetradingpost.com/sumner ... index.html

HERES OTHER INFO LINKS that were posted elseware but I found them useful

http://www.wallaceracing.com/reargear.htm

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://users.erols.com/srweiss/transc.htm#tabtop

http://users.erols.com/srweiss/transc.htm#Auto

Beach Bum said:
think a lot of people do not understand the effect of gearing the 700R4 has on the most important gear for acceleration, which is 1st gear. To give people a better idea of the effect, the bestway is to compare it to the th350 or th400 with the type of gears they ran yesteryear..... and look at the final ratio assuming the same tire height.

Going out of memory, the th350 has a 2.52 first gear ratio, thus here are few of the final gear ratio's of 1st gear:

2.52 x 3.23 = 8.13
2.52 x 3.45 = 8.69
2.52 x 3.73 = 9.39
2.52 x 4.11 = 10.35
2.52 x 4.56 = 11.49

Here are the same gear ratio's plus a few common C4 ratio's with a 700R4:

3.06 x 2.59 = 7.92
3.06 x 2.73 = 8.35
3.06 x 3.07 = 9.39
3.06 x 3.23 = 9.88
3.06 x 3.45 = 10.55
3.06 x 3.73 = 11.41
3.06 x 4.11 = 12.57
3.06 x 4.56 = 13.95

As you can above, a 3.07 gear with a 700R4 is actually equalivent to the old muscle years utilizing a 3.73 gear...... thus, the 3.07 gear is really the modern 3.73 gear. 3.45 gears are actually more gear than 4.11s with a th350.......

With a stock L98 motor that makes its HP peak even before 5000 rpm...... you just do not need much gear, you can actually be over gearing your motor to the point it accelerates too fast through your torque curve. Its hard for me to describe, but it happens all the time.

As a note, years ago, I did a before and after in-depth dragstrip test on a 3.07 vs 3.45 gears. I had been bracket racing the 3.07 gears for many years and knew my car to the hundredths.... I switched to the 3.45 gears, on the street after it was done, I would have swore my car was going to be faster at the strip...... then the weekend came and reality hit in the form of a timeslip that showed no difference in et's or traps at all..... in fact, I might have slowed down a hundredths, but hard to tell. This was on a 383 Superram motor that made a little over 400 HP with a HP peak in the mid 5000's. It too was a torque laden motor, but without a lot of HP and a tight rpm band, just like your TPI motor.

The 3.07's are probably best for pure performance in your set-up if you have a slightly loose torque converter......which incidently, a good converter is more important than gear with your TPI motor.

good luck with whatever you choose !
 
:mrgreen:

I like many of your old readings Grumpy.
Lots of info. Like a Long Lost Treasure Discovered again.
Bookmarked.
 
The Bolt on Overdrive Units have always been an option I like Grumpy.
Gear Vendors comes to mind. Some minor fabrication to use one.
Always wanted one for the 70 TA.
Best of both worlds. Low Rear End Gears. 4.30-4.88. Hit overdrive button. 3 series gear again.
Expensive still. But good to 2,000 HP.
Awriteup on them by you recommended.
Someday I want One.
 
heres a darn good couple of chart's showing the effect on the cars lap time's that the selection of the correct rear gear ratio had, keep in mind this will need to be tested with every engine and drive train combo, and obviously the type of track, or speeds and tire diameter , your engines power curve, the car weight and the suspensions and tires will effect the results

FInal%2BDrive%2Bgraph%2B-%2Bgingerman.JPG


Final%2BDrive%2BGraph%2B-%2Bwaterford.JPG
 
heres a darn good couple of chart's showing the effect on the cars lap time's that the selection of the correct rear gear ratio had, keep in mind this will need to be tested with every engine and drive train combo, and obviously the type of track, or speeds and tire diameter , your engines power curve, the car weight and the suspensions and tires will effect the results

FInal%2BDrive%2Bgraph%2B-%2Bgingerman.JPG


Final%2BDrive%2BGraph%2B-%2Bwaterford.JPG
Hi grumpy, I am close to putting 4.09 gears into my truck to replace the 3.54 ring and pinion that currently is in there. Motor is a 400 sbc with a t700r. I have a 28 " tire. My understanding is that the new ratio will feel like a 3.80 with a 26" tire. I have achieved this math by dividing 26 by 28 which equates to .93 , then multiplying by 4.09 which equates to 3.80 . This is for a 1:1 drive ratio in third, with the .7 overdrive in drive this final drive ratio equates to 2.66 . Does this sound about right? With my current setup the 3.54 with the 28" tire definitely feels like the 3.28 the maths works out to be which is a mismatch for the lunati cam I have. Cheers
 
Thanks Grumpy, those calculators justified my maths. Cant wait to get them installed.
Will post results. Kind Regards,
 
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