muncie transmission info

grumpyvette

Administrator
Staff member
new_m22.jpg

Since the M21's come with either 10 spline in /27 spline out
or
26 spline in /32 spline out input/output spline counts

http://www.5speeds.com/racing/m22x.html

http://www.5speeds.com/case.html (SUPER CASE UPGRADE)

http://www.nastyz28.com/index.php?page= ... ansmission

http://www.drivetrain.com/parts_catalog ... umber.html

http://www.drivetrain.com/parts_catalog ... l_kit.html

http://www.5speeds.com/muncie2.htm

http://www.4speeds.com/video.html

http://www.tbtrans.com/muncie_4_speed.htm

http://www.highperformancepontiac.com/t ... index.html

http://www.yearone.com/updatedsinglepag ... muncie.asp

http://www.hemmings.com/mus/stories/200 ... ure18.html

http://www.4speeds.com/muncie2.htm

http://www.4speeds.com/muncie3.htm

http://www.4speeds.com/newm22.html
gmtrow.png

keep in mind theres three common throw out bearing heights and youll need the correct height for your particular application to get proper clutch function
Case casting numbers, relating production years and ratios available

Casting: 3831704 Years: 1963 Only Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3851325 Years: 1964 - 1965 Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3885010 Years: 1965 - 1967 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925660 Years: 1968 - 1970 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925661 Years: 1970 - 1974 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st

Ratios of the M20 , M21 , M22

Year 1963-1965 Type: M20 Rings: None Ratio: 2.56 / 1.91 / 1.48 / 1.00 / 3.16
Year 1966-1974 Type: M20 Rings: Two Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Rings: One Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
Year 1967-1974 Type: M22 Rings: None Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27

Input Shaft Tooth and Spline Count Related to Year

Year 1963-1965 Type: M20 Rings: None Spline: 10 Tooth Count: 24
Year 1966-1970 Type: M20 Rings: Two Spline: 10 Tooth Count: 21
Year 1970-1974 Type: M20 Rings: Two Spline: 26 Tooth Count: 21
Year 1963-1970 Type: M21 Rings: One Spline: 10 Tooth Count: 26
Year 1970-1974 Type: M21 Rings: One Spline: 26 Tooth Count: 26
Year 1967-1970 Type: M22 Rings: None Spline: 10 Tooth Count: 26
Year 1969-1974 Type: M22 Rings: None Spline: 26 Tooth Count: 26
Please note that there are 7 different Muncie input shafts. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. A common mistake is thinking that all "fine spline" 26 spline input shafts are M22 heavy duty types. This is not true. An M22 gearbox has a 20 degree helix angle on the gearset as opposed to a 30 degree angle. It's roughly a 10 degree difference. From time to time I get people disputing what exact angles are on the gears. Personally, I think the angles vary from gear to gear. 1st gear on an M22 may be 19 degrees, 3rd may be 20 degrees. Also M22 gear sets were of a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "rockcrusher". The higher nickel alloy allowed for more impact of the gears. Another misconception is if you have a drain plug you have an M22. Again this was only true when the first M22 boxes were created. But all 3925661 castings had drain plugs.

Reading Serial and VIN Numbers

Serial numbers for Muncie 4 speeds always begin with the letter "P". P stands for Muncie Plant. Not for passenger car as some self proclaimed specialists may think. The letter M was used to ID the Muncie plant for the Muncie 3 speed, so P was the next logical letter. The letter O would add confusion since it resembles zero. The serial number is a date code the transmission was built for a particular year. Serial numbers from 1963 to 1966 included only the month and day. P0101 would indicate January 1st. From 1967 to 1968 the serial number got a year designator and a letter designator for the month such as P8A01, meaning January 1st 1968. One important point is that if you have a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13. This is for a 1968 production car. The T stands for December and 13 is the day. To confirm this simply look at the VIN number. It will usually begin with a 18S101350 or a 28N12950. This means the Muncie was assembled December 13, 1967 for the 1968 model year. The VIN number will usually be a low number. 1969 to 1974 Muncies got a ratio designator at the end of the serial number. An example would be P4D23B. This equates to April 23, 1974, M21 ratio.


Month Code Chart


January Letter: A May Letter: E September Letter: P
February Letter: B June Letter: H October Letter: R
March Letter: C July Letter: K November Letter: S
April Letter: D August Letter: M December Letter: T

Ratio Code Chart


Letter: A M20 Ratio
Letter: B M21 Ratio
Letter: C M22 Ratio
Important Notes
Some input shafts produced by the aftermarket and General Motors have no identifying rings on them. The rings originally corresponded with rings or grooves on the counter gear so that the assembler matched a one or two ring input with a one or two ring cluster. When manufacturing was stopped, GM stopped making inputs with these marks, probably to save machining operations. Also 3831704 and 3851325 castings come with a 7/8" counter shaft all others come with a 1 inch counter shaft. There are some odd ball castings out there produced in 1963 to 1966 years. I've left them out since they really are not common.




Several things are needed to identify a Muncie correctly. The first is a main case casting number. Second a count of the input shaft and output shaft splines and if any rings or grooves exist around the input shaft splines. Third are date codes and VIN numbers that help confirm that the above case and gears belong together. Tooth counts on the input shaft will help confirm a certain gear ratio, but you may not have access to this information if the transmission is still in the car or an unwilling vendor at a swap meet won't remove the cover.


Case casting numbers, relating production years and ratios available


Casting: 3831704 Years: 1963 Only Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3851325 Years: 1964 - 1965 Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3885010 Years: 1965 - 1967 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925660 Years: 1968 - 1970 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925661 Years: 1970 - 1974 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Ratios of the M20 , M21 , M22


Year 1963-1965 Type: M20 Rings: None Ratio: 2.56 / 1.91 / 1.48 / 1.00 / 3.16
Year 1966-1974 Type: M20 Rings: Two Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Rings: One Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
Year 1967-1974 Type: M22 Rings: None Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
Input Shaft Tooth and Spline Count Related to Year


Year 1963-1965 Type: M20 Rings: None Spline: 10 Tooth Count: 24
Year 1966-1970 Type: M20 Rings: Two Spline: 10 Tooth Count: 21
Year 1970-1974 Type: M20 Rings: Two Spline: 26 Tooth Count: 21
Year 1963-1970 Type: M21 Rings: One Spline: 10 Tooth Count: 26
Year 1970-1974 Type: M21 Rings: One Spline: 26 Tooth Count: 26
Year 1967-1970 Type: M22 Rings: None Spline: 10 Tooth Count: 26
Year 1969-1974 Type: M22 Rings: None Spline: 26 Tooth Count: 26
Please note that there are 7 different Muncie input shafts. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. A common mistake is thinking that all "fine spline" 26 spline input shafts are M22 heavy duty types. This is not true. An M22 gearbox has a 20 degree helix angle on the gearset as opposed to a 45 degree angle. Also M22 gear sets were of a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "rockcrusher". The higher nickel alloy allowed for more impact of the gears. Another misconception is if you have a drain plug you have an M22. Again this was only true when the first M22 boxes were created. But all 3925661 castings had drain plugs.


Reading Serial and VIN Numbers


Serial numbers for Muncie 4 speeds always begin with the letter "P". P stands for Muncie. Why.... I have no idea. The serial number is a date code the transmission was built for a particular year. Serial numbers from 1963 to 1966 included only the month and day. P0101 would indicate January 1st. From 1967 to 1968 the serial number got a year designator and a letter designator for the month such as P8A01, meaning January 1st 1968. One important point is that if you have a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13. This is for a 1968 production car. The T stands for December and 13 is the day. To confirm this simply look at the VIN number. It will usually begin with a 18S101350 or a 28N12950. This means the Muncie was assembled December 13, 1967 for the 1968 model year. The VIN number will usually be a low number. 1969 to 1974 Muncies got a ratio designator at the end of the serial number. An example would be P4D23B. This equates to April 23, 1974, M21 ratio.


Month Code Chart


January Letter: A May Letter: E September Letter: P
February Letter: B June Letter: H October Letter: R
March Letter: C July Letter: K November Letter: S
April Letter: D August Letter: M December Letter: T
Ratio Code Chart


Letter: A M20 Ratio
Letter: B M21 Ratio
Letter: C M22 Ratio
Important Notes


Some input shafts produced by the aftermarket and General Motors have no identifying rings on them. The rings originally corresponded with rings or grooves on the counter gear so that the assembler matched a one or two ring input with a one or two ring cluster. When manufacturing was stopped, GM stopped making inputs with these marks, probably to save machining operations. Also 3831704 and 3851325 castings come with a 7/8" counter shaft all others come with a 1 inch counter shaft. There are some odd ball castings out there produced in 1963 to 1966 years. I've left them out since they really are not common.
Main Case

3831704 1963 Only small 6207NR Front Bearing ,Pat. Pending, 7/8" Bore
3839606 1963 - 1964 Regular Bearing Pat. Pending, 7/8" Bore
3864_____ 1964 Milled off last 3 digits 7/8" Bore Patent Pending
3851325 1964 -1965 7/8" Bore Patent Pending Mostly 1964
3851325 1964 –1965 7/8" Bore Patent Number
3885010 1966 -1967 1" Bore Patent Number
3925660 1968 – 1970 1" Bore Patent Number
3925661 1970 – 1974 (some early 1975 cars) 1" Bore Patent Number


Tailhousing

3831731 1963 "Thin Fin Tail" Driver speedo 27 spline
3846429 1963 "Thin Fin Tail" Driver speedo 27 spline
3846429 1963-1965 Regular thick web, driver speedo, 27 spline
9779246 1964 – 1965 Pontiac Catalina Long Tail Driver Speedo 27 Spline
3857584 1966 – 1970 Passenger side speedo, 27 spline
3978764 1970 – 1974 passenger speedo, 32 spline output


Side Cover

3831707 1963-1965 Early side cover stud type shift shafts
3884685 Cover issued with "584" tail stud type shift shafts
3950306 Short boss with bolt on type shift shafts - no switches
3952642 Long boss bolt on type w/ TCS switch on 3-4
3952648 Short boss bolt on type w/ TCS switch on 3-4

335308 Long boss bolt on type with neutral safety switch. Some have a boss for the switch that is cast but not machined on 1-2.
 
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http://www.highperformancepontiac.com/t ... index.html

http://www.garagemotorsports.com/muncie.htm

http://tbtrans.com/muncie_4_speed.htm#diagram

http://www.tbtrans.com/muncie_4_speed.h ... parts_list

http://www.wolferacecraft.com/pinionangle.aspx

http://www.hotrodhotline.com/conten...ancellation-jim-clark-hot-rod-md#.WRKEkfnyvcc

http://www.5speeds.com/muncie2.htm

http://www.5speeds.com/muncie3.htm

http://www.gearvendors.com/hrgm4sm.html

http://www.5speeds.com/case.html (SUPER CASE UPGRADE)

http://www.superchevy.com/how-to/additional-tech/1606-how-to-identify-a-muncie-four-speed/

http://www.chevydiy.com/muncie-4-speed-the-complete-history/

http://www.secondchancegarage.com/public/muncie-4-speed.cfm

https://www.midwestmuncie.com/

http://www.superchevy.com/how-to/tr...-speed-build-date-codes-vins-and-input-shaft/


viewtopic.php?f=45&t=1674&p=4065&hilit=+linkage#p4065

viewtopic.php?f=71&t=2936&p=7698&hilit=hurst+linkage#p7698
Main Case
3831704 1963 Only small 6207NR Front Bearing ,Pat. Pending, 7/8" Bore
3839606 1963 - 1964 Regular Bearing Pat. Pending, 7/8" Bore
3851325 1964 -1965 7/8" Bore Patent Pending Mostly 1964
3851325 1964 –1965 7/8" Bore Patent Number
3864848 1965 7/8" Bore Patent Number ( rare )
3864_____ 1965 Milled off last 3 digits 7/8" Bore Patent Number
3885010 1966 -1967 1" Bore Patent Number
3925660 1968 – 1970 1" Bore Patent Number
3925661 1969 – 1974 (some early 1975 cars) 1" Bore Patent Number

Tailhousing
3831731 1963 "Thin Fin Tail" Driver speedo 27 spline
3846429 1963 "Thin Fin Tail" Driver speedo 27 spline
3846429 1963-1965 Regular thick web, driver speedo, 27 spline
Used up to 1970 in some Pontiac Models
384362 1963 – 1964 Long Tail Driver Side Speedo 27 Spline
9779246 1964 – 1965 Pontiac Catalina Long Tail Pass. Speedo 27 Spline
3857584 1966 – 1970 Passenger side speedo, 27 spline
3978764 1970 – 1974 passenger speedo, 32 spline output

Side Cover
3831707 1963-1965 Early side cover stud type shift shafts
3884685 Cover issued with "584" tail stud type shift shafts
3950306 Short boss with bolt on type shift shafts - no switches
3952642 Long boss bolt on type w/ TCS switch on 3-4
3952648


Short boss bolt on type w/ TCS switch on 3-4
335308 Long boss bolt on type with neutral safety switch.
Some have a boss for the switch that is cast but not machined on 1-2.

GTR1999 POSTED THIS INFO
Muncie and ST-10 trans are not up to the level of power you might want want to use. They just won't handle the abuse. I believe but haven't looked it up, they are rated about 300 ft/lb torque. My son has blown up 2-3 trans in the past 2 years. He's looking into better trans now and of course they're costly.

The super case is made better but I don't know if they're rated for levels in the 500+ range. Some have said they bear them up pretty good but I haven't tested one to say for sure. A new built super case is about $2000.

Here's a super T-10 after some abuse in the 450hp range.

crackedtailhousing.jpg


CrackedRHcase.jpg



crackedcase1.jpg


brokenmidplate.jpg


brokencountershaft.jpg



eature Article from Hemmings Muscle Machines
April, 2004

We have mentioned several transmission swaps over the last 6 months, but another one definitely worth mentioning involves using the Muncie 4-speed. They are a very popular transmission with Chevrolet enthusiasts, and are easily adaptable for a wide range of GM and other non-GM vehicles.
First appearing in the 1963 Chevrolet full-size cars and Corvettes, they were originally available with two first-gear ratios, 2.20:1 and 2.56:1. As GM phased out use of the Borg-Warner T-10 in 1963, the 2.56:1 ratio became standard equipment for 4-speed applications in the 1964 Chevelle, Nova and Olds F-85/Cutlass. These early units went through design changes in their youth, and the 1963-65 units, because of the smaller input shaft, are not the best transmissions to use in a swap, but it is possible. The easier solution would be to find one of the more standardized 2.52:1 or 2.20:1 Muncies that were used from 1966-74. This is when GM made the production change to the Borg-Warner Super T-10.
When looking for a Muncie 4-speed, there are many available at local swap meets or Chevy car shows. The first thing to look for with the Muncie is the side cover. Seven bolts hold on the side cover, 2 bolts on the bottom, 3 bolts on the top and one down each side. There are 2 -3/8-inch studs for the shifter levers protruding from the side cover. Similar in appearance to the Saginaw 4-speed, the Muncie's side cover is more irregular shaped, the top of the cover being noticeably wider than the bottom. Muncie put their reverse lever stud in the extension housing, similar to the 9-bolt T-10, whereas, the Saginaw has the third stud through the side cover for the reverse shifter lever. All Muncie transmission cases are made of aluminum, which helps in identifying it as well.
These 5 casting numbers identify all aluminum Muncie main cases:

3831704 - 1963 only
3851325- 1964-65
3885010- 1965-67
3925660- 1968-70
3925661- 1971-74


The 2.20 ratio is commonly designated as the M21 transmission, while the 2.56 ratio is commonly referred to as an M20. Muncie also had a second close-ratio transmission called an M22, which enthusiasts christened Rockcrusher; this was used in performance big-block engines and Corvettes and is a highly sought-after performance transmission today, and is the heavy-duty version of the 2.20 ratio M21 4-speed. The later-model 1971-74 units are more popular with drag racers, because the 27-spline output is stronger, and better absorbs the higher rpms required when the cars first launch away from the staging lights.
Early models (1963-70) had a 10-spline input shaft configuration; 1971-74 used a 26-spline input shaft. The tailshaft spline also changed in 1971. The later 27-spline output is the same as was used on the automatic transmissions; however, the yokes are not always the same in length. This makes it a good idea to try to purchase the entire assembly of transmission, shifter, bellhousing and driveshaft whenever possible. It will save you from having to hunt down the correct component pieces after you are into the installation. Clutch discs, flywheels, tailshaft yokes, and in some cases starters, will be different on some applications. Grooves on the spline of the input shaft can identify all three of these units. GM marked these units in this way so they could be told apart on the production line during assembly and installation. Some rule-of-thumb spline-groove identification information:

1963-65 M20 2.56 ratio 10-spline 7/8-in. shaft - no grooves- 27-spline output shaft
1966-70 M20 2.52 ratio 10-spline 1-in. shaft - 2 grooves - 27-spline output shaft
1971-74 M20 2.52 ratio 26-spline 1-in. shaft - 2 grooves - 32-spline output shaft
1963-65 M21 2.20 ratio 10-spline 7/8-in. shaft - 1 groove - 27-spline output shaft
1966-70 M21 2.20 ratio 10-spline 1-in. shaft - 1 groove - 27-spline output shaft
1971-74 M21 2.20 ratio 26-spline 1-in. shaft - 1 groove - 32-spline output shaft
1965-70 M22 2.20 ratio 10-spline 1-in. shaft - no groove - 27-spline output shaft
1971-74 M22 2.20 ratio 26-spline 1-in. shaft - no groove - 32-spline output shaft


GM made it a little easier to identify these transmissions when they started using a letter designation on the end of the build code on 1969 models:

A- M20 2.52 ratio (wide)
B- M21 2.20 ratio (close)
C- M22 2.20 ratio HD (close)


Normally, cars with a rear end ratio less than 3.55 would not come originally with the M22 close-ratio. The main case oil pans on the M20 and M21 did not have a fluid drain plug before 1970, whereas the M22 came with the drain plug in all years. Because aftermarket input shafts do not have the "grooves" designations, the only true way to know if you have the M22 Rockcrusher ratio is to open the unit and check the cluster gear. If the helix angle is shallow (around 20 degrees), chances are you have the M22, or someone has upgraded to the M22 gears. The M22 gears are also made of a higher-grade nickel alloy. The M20 and M21 cluster gears are cut at a 45-degree angle, and this smaller gear angle created a problem with noise (hence the name Rockcrusher). Performance seekers decided to live with the noise when the performance benefits of the gear cut outweighed the gravelly clatter. If you are not able to locate one of these units, and you really have your heart set on one, there are parts available to upgrade your M20 or M21 to an M22 Rockcrusher from several Muncie parts specialists.
So now that we know what we are looking for, the question is where do we find them? For the most part, any mid-size A-, G-, X- or F-Body GM vehicle from 1964-74 could potentially have the transmission you are looking for.
10-spline units came in these vehicles:

1964-70 Chevy Corvettes and Pontiac Tempest
1967-70 Buick Special, Firebird and Camaro
1969-70 Grand Prix
1963-69 Impala
1965-70 Nova and Olds Cutlass/F-85 and Chevelle (except 1970 w/454-cu.in. V-8)
1970 Monte Carlo

26-spline units came in these vehicles:


1970 Chevelle 454
1971 Grand Prix and Monte Carlo
1971-72 Special and Tempest
1971-73 Nova, F85 and Cutlass
1971-74 Firebird, Camaro, El Camino, Corvette, Chevelle and Sprint
1973 Buick Century
1973-74 Pontiac Le Mans


Used units can be found at your local salvage yard for between $400 and $900 depending on year, ratio and condition. A recent ad in Hemmings Motor News priced a rebuilt M21 at $1,250, and new aftermarket M22s are selling in the $1,400 to $2,500 range. This means that even with a $150 rebuilding kit, you can save some big money by getting your hands a little dirty and spending an afternoon counting splines and grooves.
Some additional swap information to help you determine how easily a Muncie will fit into your GM car:
GM vehicles with a Turbo 350 or Powerglide automatic can use a Muncie 4-speed without having to modify your original driveshaft. Other GM automatic transmissions sharing the same 27-spline output are the Turbo 350, 200-4R and 700R-4.
The Turbo 400 uses a 32-spline output and the case is 3-inches longer, so it would be a more difficult swap. The TH400 yoke will work on the 1971-74 M22s however the driveshaft would have to be shortened.
Aftermarket shifters are still readily available for the Muncie, as well as clutch components and flywheels.
In the case of GM automatics, the transmission mount is the same for the Muncie as the Turbo 350, 200-4R and the 700-R4.
For all you non-GM readers, thanks for reading on; thought I wasn't going to get to you, didn't you? There are adapters available from Bendtsen's, Hayes and Wilcap, or your local speed shop that make the swap into your car possible as well. Adapter kits allow the Muncie to be put behind many different engines. Here are some adapter kits and adapter bell housings that are available:

AMC V-8
Buick V-6
Buick Nailhead
Cadillac Flathead
Buick Straight-8
Chrysler 1951-53 Hemi
Chrysler 1954-59 Hemi
Chrysler 1954-59 Polys
Chrysler Flathead
Ford FE V-8
Pontiac Straight-8
Ford small-block and 351 Cleveland (6-bolt block mount)
Chrysler small-block

There are even transfer case adapters available to allow you to use the Muncie in 4-wheel drive applications.
So, as you can see, it is possible to put a Muncie in your Mustang or Barracuda as well as your De Soto or Chieftain. These adapters are expensive; some are as much as an additional $700. But for the advantages to a bracket racer or the boulevard cruiser for that matter, the money to invest for a quicker machine is well worth it.

This article originally appeared in the April, 2004 issue of Hemmings Muscle Machines.
 
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I recently helped my brother-in-law replace the clutch in his 1974 corvette project car, now if youve never replaced the clutch in a C3 corvette I can assure you that its not all that easily done as the cross member makes removing the transmission a P.I.T.A.
The car came with a 11" clutch and pressure plate when we got it, I don,t know if it was original but it looked like OEM Chevy parts so it was not designed for high performance use!
he didn,t want to spend the cash for a billet flywheel or blow proof bell housing which I feel is a huge mistake, but hey, its his feet and car!
anyway I got a decent quality diaphragm 11" clutch, pressure plate disc and throw out bearing installed ,purchased from hays clutches and eventually got the clutch and shifter linkage correctly adjusted so he can speed shift and destroy the rear tires after it was correctly tuned.
we also upgraded the distributor and replaced the points with a newer ignition.

TOM at DZAUTO posted this good info
BTW All muncies have a place to install a drain but few are factory drilled and tapped
mun1m.jpg

drill a properly centered 1/8" hole
mun2m.jpg

drill the hole to 11/16"
mun5m.jpg

The hole is then tapped with a 1/2in pipe tap.
mun3m.jpg

mun6m.jpg

mun4m.jpg

With a magnetic drain plug installed, the oil can be drained and changed, BUT, it also permits removal of any metal particles which can continue to circulate in the tranny and cause continued wear to gear teeth and bearings.

viewtopic.php?f=45&t=1674&p=4065&hilit=shifter+adjusting+linkage#p4065

viewtopic.php?f=71&t=447

viewtopic.php?f=71&t=3544&p=9417&hilit=u+joints+corvette#p9417

viewtopic.php?f=33&t=80&p=5408&hilit=u+joints+corvette#p5408

viewtopic.php?f=71&t=1538&p=3540&hilit=u+joints+corvette#p3540
 
There was a different 1st gear ratio for the 1965 Muncie M22 than listed as 2.20 to 1 as often published.
1965 M22 was an option for the 1965 Chevelle Z11 396 BBC & 1965 Corvette 396 solid lifter BBC.
I am going to research in my old 1980's car magazines but I recall the 1965 M22 had a 1st gear ratio of somewhere of 2.42 to 2.64 to 1.
So the the 1965 M22 had a very unique clutch gear input shaft & counter gear tooth count assembly, 7/8 inch diameter counter shaft.

Very comprehensive listing & detailed information on 1963 to 1974 Muncie 4-speeds I have never seen before in 1 place as posted here on Grumpy's site.

Brian
 
muncie m21 rear drive shaft seal

Muncie & Saginaw Extension Tail Housing REAR SEAL & BUSHING Transmission

http://www.ecklerscorvette.com/corvette ... -1977.html

http://stores.ebay.com/THE-GEAR-BOX?_tr ... 7675.l2563

GM Tail Shaft Seal Muncie Powerglide Corvette Camaro Chevelle 1243402
munn1.jpg

munn2.jpg

munn3.jpg


THE manual transmission in the 1974 big block corvette I was working on needed a rear seal replaced,
I pulled out the old one and found embossed on the seal was the numbers 18658 ,
its internal seal diam. is 1.875",
the outer diameter that presses into the tail shaft measures 2.75"
the listed part number at Bennett auto parts is #472572
sop this is a totally different seal than the one listed at ecklers and several other vendors
the cost was $19.95

I found this info listed
18658
Manufactured by CR OIL BATH SEALS
CHICAGO RAWHIDE
OIL SEAL 1.875 X 2.750 X .313INCH
Weight: 0.026 lbs
OBSOLETE
 
its a real good idea when you buy brakes, belts or hoses, spark plugs, freeze plugs, wheel studs, etc. to bring the old pads or shoes , belts or hoses to the store so you can visually compare the parts the guys selling you , I don,t know why but I have seen several times where the package of brake pads or brake shoes,hoses, plugs etc. or belts bare little or no resemblance to the old ones, your replacing.
if you are buying bearings or bearing seals , or suspension components , wheel bearings and a dozen other components having a caliper handy to measure and actually comparing the parts side bye side is a good idea also, its also a good idea to clean the older parts in a good solvent and brush and dry them so you can look for part numbers or brand names.
Feeler-Gauge.jpg

calipersaa.jpg


Saginaw Transmission Gear Ratio Identification.

Saginaw 3-speed 1st 2nd 3rd
No Lines (grooves) 2.85 1.68 1.00
1 Line (groove ) 2.54 1.50 1.00
2 Lines (grooves) 3.11 1.84 1.00
3 Lines (grooves) 3.50 1.89 1.00
Others found but not with complete specs:
------------------2.54 1.88 1.00

Saginaw 4-speed 1st 2nd 3rd 4th
No lines (grooves) 2.84 2.01 1.35 1.00
1 Line (groove ) 2.54 1.80 1.44 1.00
2 Lines (grooves) 3.11 2.20 1.47 1.00
3 Lines (grooves) 3.50 2.47 1.65 1.00
Others found but not with complete specs:
-------------------2.20 1.64 1.47 1.00

Muncie Transmission Gear Ratio Identification

Transmission Year 1st 2nd 3rd 4th
M-20 wide ratio 63-65 2.56, 1.91, 1.48, 1.00
M-20 wide ratio 66-70 2.52, 1.88, 1.46, 1.00
M-20 wide ratio 71-74 2.52, 1.88, 1.46, 1.00
M-21 close ratio 63-65 2.20, 1.64, 1.28, 1.00
M-21 close ratio 66-70 2.20, 1.64, 1.28, 1.00
M-21 close ratio 71-74 2.20, 1.64, 1.28, 1.00
M-22 close ratio 65-69 2.20, 1.64, 1.28, 1.00
M-22 close ratio 70-74 2.20, 1.64, 1.28, 1.00
Others found but not with complete specs:

Borg Warner Transmission Gear Ratio Identification

Transmission Years 1st, 2nd, 3rd, 4th Spline
T-10 Close Ratio 57-62 2.20, 1.66, 1.31, 1.00
T-10 Close Ratio 62-65 2.20, 1.64, 1.31, 1.00 aka T10C, T10F, T10K
T-10 Wide Ratio 61-62 2.54, 1.92, 1.51, 1.00 aka T10A
T-10 Wide Ratio 62-65 2.54, 1.89, 1.51, 1.00 aka T10D, T10E, T10G
T-10 Close Ratio 64-65 2.20, 1.64, 1.31, 1.00
Others found but not with complete specs:
2.36 1.62 1.20 1.00 aka T10M
2.54 1.74 1.30 1.00 aka T10N
2.36 1.78 1.41 1.00 aka T10B
2.36 1.76 1.41 1.00 aka T10J T10L
2.73 2.04 1.50 1.00 aka T10H



ST-10 74-95 2.43, 1.61, 1.23, 1.00 aka T10S
ST-10 74-95 2.64, 1.75, 1.33, 1.00 aka T10W
ST-10 74-95 2.88, 1.91, 1.33, 1.00 aka T10CC
ST-10 74-95 3.42, 2.28, 1.46, 1.00 aka T10Z
Others found but not with complete specs:
2.43 1.76 1.47 1.00 aka T10P
3.44 2.28 1.46 1.00 aka T10U
2.23 1.77 1.35 1.00 aka T10V
2.64 1.60 1.23 1.00 aka T10X
2.88 1.74 1.33 1.00 aka T10Y
3.29 1.72 1.00 0.80 aka T10AA
4.17 2.28 1.46 1.00 aka T10BB
2.64 2.10 1.60 1.00 aka T10Q
2.64 2.10 1.46 1.00 aka T10T
2.23 1.77 1.35 1.00 aka T10V
2.99 1.86 1.33 1.00 aka ST10-99
3.08 1.86 1.33 1.00 aka ST10-99

Borg Warner T56 Transmission Gear Ratio Identification

Part# 1st 2nd 3rd 4th 5th 6th Torque Rating
-003 2.66 1.78 1.30 1.00 0.74 0.50 330 lbs/ft
-006 3.36 2.07 1.35 1.00 0.80 0.62 350 lbs/ft
-007 2.97 2.07 1.43 1.00 0.80 0.62 350 ft/lbs
-011 2.97 2.07 1.43 1.00 0.80 0.62 450 ft/lbs
-012 2.97 2.07 1.43 1.00 0.80 0.62 450 ft/lbs
-016 2.66 1.78 1.30 1.00 0.74 0.50 450 ft/lbs
-017 2.66 1.78 1.30 1.00 0.74 0.50 450 ft/lbs
-018 2.66 1.78 1.30 1.00 0.74 0.50 450 ft/lbs
-019 2.66 1.78 1.30 1.00 0.74 0.50 450 ft/lbs
-020 2.66 1.78 1.30 1.00 0.74 0.50 450 ft/lbs
-021 2.66 1.78 1.30 1.00 0.79 0.63 450 ft/lbs
-022 2.66 1.78 1.30 1.00 0.74 0.50 350 ft/lbs
-023 2.66 1.78 1.30 1.00 0.74 0.50 375 ft/lbs
-024 2.66 1.78 1.30 1.00 0.74 0.50 375 ft/lbs
-025 2.97 2.07 1.43 1.00 0.84 0.56 385 lbs-ft

Tremec Transmission Gear Ratio Identification

Standard 350 lbs-ft....3.27 1.98 1.34 1.00 0.64
Standard II 375 lbs-ft.3.27 1.98 1.34 1.00 0.83
TKO 425 lbs-ft...........3.27 1.98 1.34 1.00 0.64
TKO II 475 lbs-ft........3.27 1.98 1.34 1.00 0.83
500..........................2.87 1.89 1.28 1.00 0.64
600..........................2.87 1.89 1.28 1.00 0.82 -
----6-speed............. 3.27 1.98 1.34 1.00 0.83 0.50
----6-speed..............3.18 2.06 1.39 1.00 0.65 0.50

66FC55F.jpg

READ THIS RELATED THREAD
http://garage.grumpysperformance.com/index.php?threads/muncie-spline-count.11255/#post-57518

http://legendgt.com/Products/lgt-700/
 
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https://www.5speeds.com/muncie3.htm
https://www.5speeds.com/video.html
Identifying Muncie 4 Speeds III by Paul Cangialosi
The most popular question has to be that everyone thinks they have the famous "rockcrusher" M22 4 speed. This had the same gear ratios as the M21 but with a heavy duty gearset. The reason you may ask? Well it wasn't designed so that you could go drag racing on Saturday night or impress girls in front of Burger King by doing massive hole shots. It was primarily designed as a road race transmission. The straighter angle of the gearset produced less heat and less end loading of the gear train. Combined with high impact alloy gears this 4 speed really pushed the limits of it's aluminum case in drag race applications. Although the gears are not spur gears ( completely straight ) they still produced a fair amount of gear noise thus the "Rockcrusher" name. These 4 speeds sound like a blower drive. For the real gear head the best documented movie that sports a real M22 in a car is the famous movie " Two Lane Black Top ". You can really hear this gear box howl in the background as James Taylor and Dennis Wilson talk at a little over 3 minutes in this youtube clip. Later on we get to see the same car with new paint in the classic film "American Graffiti" with Harrison Ford at the helm. Since they used a dummy car for inside dialog shots you miss the flavor of the M22 in that flick.

pinion_angle_transmission_anle.PNG

The dead 2.20 first gear ratio which is the same in the M21 is not that good for off the line acceleration. You would need at least a 4.56 rear end gear to compensate for the dead first gear. That was OK when gas was cheap in 1967 and you did not mind pulling 3000 RPM at 50 MPH while going to work. Times and requirements have changed making both the M21 and M22 the closest ratio production 4 speeds ever produced but also not practical for today's driving habits unless road racing is your thing. The new Muncies being built today have some better ratios.Today's examples of the new car gear set ups are Mustang GT's with a 3.35 1st gear and 3.08 rear. New Camaros with a 2.68 1st gear, 3.73 rear gear and .59 overdrive. ZR1's with a 2.68 1st gear, 3.54 rear gear and a .59 overdrive. Get the picture? If you want to learn about this stuff DOWNLOAD our RPM Calculator software for windows its free.

Top countergear is an M22. Lower gear is an M20. Notice the different helix angles of the gears.

clusters.jpg



http://www.5speeds.com/cart/index.php?route=product/product&product_id=51


Below left is an M22 1st gear. Right is an M20 / M21 1st gear.

macrom22.jpg


Identifying Muncie 4 Speeds II by Paul Cangialosi
https://www.5speeds.com/muncie.htm

Muncie 4 Speed Rebuilding DVD is available now. Click here for information.
Paul's Intro
Many people are always calling me or asking me at shows on how to identify Muncie 4 speeds. Not too many people actually know what type Muncie they have and most publications have done a fantastic job of giving out wrong information. This includes performance parts books from GM as well as a multitude of poorly written "How To" articles in just about every car magazine and website around. Swap meets and the internet , especially Ebay are filled with "experts" that learn from other "experts" who learn from a great deal of misinformation on websites and forums. I also realize that as you are reading this, you probably saying, "why should I believe this guy?". I also get a great deal of crap from "experts" and those people writing those idiot articles, especially the MuncieMen and KajonMuncie Kings who just love copying my text from this website. I don't claim that my 32 years is longer than anyone elses or that I've rebuilt more units than anyone else. However we do sell more new Muncie 4 speeds than anyone else and actually design and make several transmissions and a load of parts. My new book published by Cartech publications allowed me the time to visit many shops to compile data on muscle car transmissions and photograph odd ball parts.

How to become a Muncie King
Swap meets are a great place to look at transmissions. So, print out this page along with the page on castings. Rather than take my word for things simply take your print out to a show and make notes. It's a fun thing, discovering all things Muncie. You can let yourself be the judge if what I have written proves out or not.
Several things are needed to identify a Muncie correctly. The first is a main case casting number. Second a count of the input shaft and output shaft splines and if any rings or grooves exist around the input shaft splines. Third are date codes and VIN numbers that help confirm that the above case and gears belong together. Tooth counts on the input shaft will help confirm a certain gear ratio, but you may not have access to this information if the transmission is still in the car or an unwilling vendor at a swap meet won't remove the cover.
Case casting numbers, relating production years and ratios available

Casting: 3831704 Years: 1963 Only Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3851325 Years: 1964 - 1965 Ratios: M20 2.56 1st , M21 2.20 1st
Casting: 3885010 Years: 1965 - 1967 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925660 Years: 1968 - 1970 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st
Casting: 3925661 Years: 1970 - 1974 Ratios: M20 2.52 1st , M21 2.20 1st, M22 2.20 1st

Ratios of the M20 , M21 , M22

Year 1963-1965 Type: M20 Rings: None Ratio: 2.56 / 1.91 / 1.48 / 1.00 / 3.16
Year 1966-1974 Type: M20 Rings: Two Ratio: 2.52 / 1.88 / 1.46 / 1.00 / 3.11
Year 1963-1974 Type: M21 Rings: One Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27
Year 1967-1974 Type: M22 Rings: None Ratio: 2.20 / 1.64 / 1.28 / 1.00 / 2.27

Input Shaft Tooth and Spline Count Related to Year

Year 1963-1965 Type: M20 Rings: None Spline: 10 Tooth Count: 24
Year 1966-1970 Type: M20 Rings: Two Spline: 10 Tooth Count: 21
Year 1970-1974 Type: M20 Rings: Two Spline: 26 Tooth Count: 21
Year 1963-1970 Type: M21 Rings: One Spline: 10 Tooth Count: 26
Year 1970-1974 Type: M21 Rings: One Spline: 26 Tooth Count: 26
Year 1967-1970 Type: M22 Rings: None Spline: 10 Tooth Count: 26
Year 1969-1974 Type: M22 Rings: None Spline: 26 Tooth Count: 26
Please note that there are 7 different Muncie input shafts. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. A common mistake is thinking that all "fine spline" 26 spline input shafts are M22 heavy duty types. This is not true. An M22 gearbox has a 20 degree helix angle on the gearset as opposed to a 30 degree angle. It's roughly a 10 degree difference. From time to time I get people disputing what exact angles are on the gears. Personally, I think the angles vary from gear to gear. 1st gear on an M22 may be 19 degrees, 3rd may be 20 degrees. Also M22 gear sets were of a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "rockcrusher". The higher nickel alloy allowed for more impact of the gears. Another misconception is if you have a drain plug you have an M22. Again this was only true when the first M22 boxes were created. But all 3925661 castings had drain plugs.

Reading Serial and VIN Numbers

Serial numbers for Muncie 4 speeds always begin with the letter "P". P stands for Muncie Plant. Not for passenger car as some self proclaimed specialists may think. The letter M was used to ID the Muncie plant for the Muncie 3 speed, so P was the next logical letter. The letter O would add confusion since it resembles zero. The serial number is a date code the transmission was built for a particular year. Serial numbers from 1963 to 1966 included only the month and day. P0101 would indicate January 1st. From 1967 to 1968 the serial number got a year designator and a letter designator for the month such as P8A01, meaning January 1st 1968. One important point is that if you have a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13. This is for a 1968 production car. The T stands for December and 13 is the day. To confirm this simply look at the VIN number. It will usually begin with a 18S101350 or a 28N12950. This means the Muncie was assembled December 13, 1967 for the 1968 model year. The VIN number will usually be a low number. 1969 to 1974 Muncies got a ratio designator at the end of the serial number. An example would be P4D23B. This equates to April 23, 1974, M21 ratio.

Month Code Chart

January Letter: A May Letter: E September Letter: P
February Letter: B June Letter: H October Letter: R
March Letter: C July Letter: K November Letter: S
April Letter: D August Letter: M December Letter: T

Ratio Code Chart

Letter: A M20 Ratio
Letter: B M21 Ratio
Letter: C M22 Ratio
Important NotesSome input shafts produced by the aftermarket and General Motors have no identifying rings on them. The rings originally corresponded with rings or grooves on the counter gear so that the assembler matched a one or two ring input with a one or two ring cluster. When manufacturing was stopped, GM stopped making inputs with these marks, probably to save machining operations. Also 3831704 and 3851325 castings come with a 7/8" counter shaft all others come with a 1 inch counter shaft. There are some odd ball castings out there produced in 1963 to 1966 years. I've left them out since they really are not common

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look over the links
notice theres an over drive top gear ratio,
for the muncie 4th gear conversion

USE A GOOD GEAR LUBE, MANY PEOPLE SAY THE NON-SYNTHETIC LUBE WORKS MARGINALLY BETTER,
ie SHIFTES A BIT SMOOTHER, BUT THE SYNTHETIC GEAR OIL HAS A MUCH HIGHER TEMPERATURE LIMIT,

BUY TWO QUARTS YOUR MUNCIES USES ABOUT 1.75 QUARTS




READ LINKS

http://www.gearvendors.com/hrgm4sm.html
http://www.gearvendors.com/hrgmratios.html

343saginaw.jpg

Standard Saginaw 3-speed transmission

hd3-speed.jpg

Heavy Duty full synchromesh 3-speed Borg Warner T16 delivered as the base transmission when the SS396 series was ordered.

The special 3-speed H.D. transmission was standard on SS396 series and optional under RPO M13 in other series and the shifter was floor mounted whether a console was ordered or not.

Gear Ratio 283 V8 and 6-cyl engines 327 and 396 V8 engines
First 2.86:1 2.41:1
Second 1.72:1 1.57:1
Third 1.00:1 1.00:1
Reverse 2.86:1 2.41:1
4_speed_speedo_exit.jpg

4spdmuncie.jpg

Muncie 4-speed manual transmission. Note the speedometer cable exit on the passenger side. Because the speedometer cable exited on the passenger side, an extra hole was required in the firewall to accommodate the speedometer cable.

4-spd-speedo-hole.jpg


p0221.jpg

P0221 (February 21) date stamping on 1966 Muncie 4-speed transmission.

p7c09.jpg

P7C09 (March 9) date stamping on a 1967 Muncie 4-speed transmission; (1967 was the first year to have the year stamped in the date code and the month represented by a letter code).

451muncie.jpg
452muncie.jpg

1964 to 1968 Muncie 4-speed transmissions can be identified from later models by the way the transmission arms attach. Early Muncie side covers had a stud and the shift arm attached with a nut on the stud while the 1969 and later model side covers had a hole and the shift arms attached with a bolt.

441saginaw.jpg

The Saginaw 4-speed transmission was also used and shown for "M20 PROD V-8 ENG & R.P.O. L30". Easily identified by the reverse gear being on the main case instead of the tail housing.

Muncie 4-Speed Identification

Casting Year(s) Ratio Ratio Ratio
3831704 1963 Only M20 2.56 1st M21 2.20 1st
3851325 1964 - 1965 M20 2.56 1st M21 2.20 1st
3885010 1965 - 1967 M20 2.52 1st M21 2.20 1st M22 2.20 1st
3925660 1968 - 1970 M20 2.52 1st M21 2.20 1st M22 2.20 1st
3925661 1970 - 1974 M20 2.52 1st M21 2.20 1st M22 2.20 1st

Years Type Ring(s) Ratio Reverse
1963 - 1965 M20 None 2.56 / 1.91 / 1.48 / 1.00 3.16
1966 - 1974 M20 Two 2.52 / 1.88 / 1.46 / 1.00 3.11
1963 - 1974 M21 One 2.20 / 1.64 / 1.28 / 1.00 2.27
1967 - 1974 M22 None 2.20 / 1.64 / 1.28 / 1.00 2.27

Years Type Ring(s) Spline Input Shaft
Tooth Count
1963 - 1965 M20 None 10 24
1966 - 1970 M20 Two 10 21
1970 - 1974 M20 Two 26 21
1963 - 1970 M21 One 10 26
1970 - 1974 M21 One 26 26
1967 - 1970 M22 None 10 26
1969 - 1974 M22 None 26 26
There are 7 different input shaft possibilities on a Muncie. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. It is commonly mistaken that all "fine spline" 26 spline input shafts are M22 transmissions. The M22 transmission has a 20 degree helix angle on the gear set as opposed to a 45 degree angle found on the M20 and M21 and were made with a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "Rock Crusher" was born. Another misconception is if you have a drain plug you have a M22. This was only true when the first M22 boxes were created; all 3925661 castings (1970-1974) had drain plugs. The M22 was only produced in a close ratio version.

If you are lucky and find the transmission tag (generally found on a lower bolt of the side cover), it will help identify a 1966 Muncie transmission. Unfortunately these metal tags are often discarded when repair or maintenance work is performed.

Engine Tag Number
RPO L34/L35 3870357 - M20
RPO L78 3890534 - M20 (after 11/5/65)
Optional 3879668 - M21 (prior to 11/5/65)
Optional 3877459 - M21
Optional 3890567 - M22 (prior to 11/4/65)
Optional 3879993 - M22 (limited sales)
Production V8 3884602 - 4 speed
RPO L30 3884603 - 4 speed
RPO L35 3890533 - M13
RPO L34/L78 3890536 - M13

3870357_trans_tag.jpg



3890534_trans_tag.jpg

The serial number is a date code and indicates the particular year the transmission was built for. Serial numbers from 1963 to 1966 included only the month and day. P0101 indicates January (first 01) 1st (second 01). In 1967 and 1968, the serial number got a year designator and a letter designator for the month such as P8A01, meaning 1968 (8), January (A) 1st (01). Note that a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13, meaning 1968 (8), December (T), 13th. The transmission was assembled December 13, 1967 for the 1968 model year. The 1969 to 1974 Muncie got a ratio designating letter at the end of the serial number. An example would be P2R25B. This decodes to 1972 (2), October (R), 25th, M21 (B).

Date Codes: A ~ January, B ~ February, C ~ March, D ~ April, E ~ May, H ~ June
K ~ July, M ~ August, P ~ September, R ~ October, S ~ November, T ~ December

Type Codes: A ~ M20, B ~ M21, C ~ M22 (1969 and newer)

Assembly Date Code Location

Transmission Code Location
3-speed (except Heavy Duty) Left side of main case, on boss below and to the rear of the side cover.
3-speed (Heavy Duty) Right side of main case, just in front of extension housing.
4-speed Right side of main case, just in front of extension housing.
Date code example:
Muncie 4-speed: P1025 P (Muncie), 1025 (October 25th)

TRANSMISSION GEAR'S RATIO 1ST 2ND 3RD 4TH
GM Standard 3-Speed Manual (L6/283) 2.85 1.68 1.00 n/a
GM Standard 3-Speed Manual (327) 2.54 1.50 1.00 n/a
GM H.D. 3-Speed Manual (L6/283) 2.86 1.72 1.00 n/a
GM H.D. 3-Speed Manual (327/396) 2.41 1.57 1.00 n/a
GM Muncie (M20) 63-65 2.56 1.91 1.48 1.00
GM Muncie (M20) 66-74 2.52 1.88 1.46 1.00
GM Muncie (M21/M22) 63-74 2.20 1.64 1.28 1.00

Transmission Gear Ratio Drop Between Gears
Standard 3-speed (L6/283) 1st to 2nd - 41.05% 2nd to 3rd - 40.48%
Standard 3-speed (327) 1st to 2nd - 40.95% 2nd to 3rd - 36.71%
H.D. 3-speed (L6/283) 1st to 2nd - 39.87% 2nd to 3rd - 41.87%
H.D. 3-speed (327/396) 1st to 2nd - 34.85% 2nd to 3rd - 36.31%
M20 (early) 1st to 2nd - 25.39% 2nd to 3rd - 22.51% 3rd to 4th - 32.43%
M20 (late) 1st to 2nd - 25.39% 2nd to 3rd - 22.34% 3rd to 4th - 31.51%
M21/M22 1st to 2nd - 25.45% 2nd to 3rd - 21.95% 3rd to 4th - 21.88%
Manual transmission part numbers

Part Number Reference Fitment
3901103 AIM - M20/A1 RPO M20 with production V-8 engine
3901104 AIM - M20/A1 RPO M20 - Optional
3890533 AIM - M20/A1 RPO M20 with RPO L30 327/275hp engine
3870357 AIM - M20/A1 RPO M20 13817-867 & RPO L35 396/325hp engine
3879668 * AIM - M20/A1 RPO M21
3879993 AIM - M20/A1 RPO M22
3873892 AIM - M10/A3 RPO M10 3-speed with overdrive
* 3879668 was 3877459 - revised in 1967 but date unreadable


Muncie 4-Speed Casting Numbers

Main Case
3831704 1963 Only small 6207NR Front Bearing ,Pat. Pending, 7/8" Bore
3839606 1963 - 1964 Regular Bearing Pat. Pending, 7/8" Bore
3864_____ 1964 Milled off last 3 digits 7/8" Bore Patent Pending
3851325 1964 -1965 7/8" Bore Patent Pending Mostly 1964
3851325 1964 –1965 7/8" Bore Patent Number
3885010 1966 -1967 1" Bore Patent Number
3925660 1968 – 1970 1" Bore Patent Number
3925661 1970 – 1974 (some early 1975 cars) 1" Bore Patent Number
Tail Housing

3831731 1963 "Thin Fin Tail" Driver speedometer 27 spline
3846429 1963 "Thin Fin Tail" Driver speedometer 27 spline
3846429 1963-1965 Regular thick web, driver speedometer, 27 spline
9779246 1964 – 1965 Pontiac Catalina Long Tail Driver Speedo 27 Spline
3857584 1966 – 1970 Passenger side speedometer, 27 spline
3978764 1970 – 1974 passenger speedometer, 32 spline output
Side Cover

3831707 1963-1965 Early side cover stud type shift shafts
3884685 Cover issued with "584" tail stud type shift shafts
3950306 Short boss with bolt on type shift shafts - no switches
3952642 Long boss bolt on type w/ TCS switch on 3-4
3952648 Short boss bolt on type w/ TCS switch on 3-4
335308 Long boss bolt on type with neutral safety switch. Some have a boss for the switch that is cast but not machined on 1-2.
 
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