replacing trans fluid


Staff member
Wanderwilly said:
I am going to change the fluid and filter on my 1994 Vette auto transmission .From what I have read I will drain about four quarts when I drop the pan. When I refill it will mix with the remaining fluid which if I understand the book correctly is a large amount.Is this O.K.? My friend next door,another car nut, gave me 5 qts. of Mobil 1 Synthetic ATF multi vehicle trans fluid. Can I use this? This is all new to me.My Vette is my hobby car.
its CRITICAL to keep the trans fluid clean and ideally changed about every 70K miles and use of a auxiliary cooler that keeps the fluid temp under about 170F is going to extend service life a good deal longer
heres a few related thread links, you might want to read thru, and Id also point out that almost any automatic transmission will have about 1/2 its fluid capacity in the transmission itself and 1/3rd-to-1/2 its fluid capacity or more in the connecting lines and the torque converter , but it could be significantly more if you installed remote mount filters and a fluid cooler , as both will potentially add a good deal more durability and fluid cooling capacity to the system.
Id also point out that adding an additional , properly sized trans cooler with the correct fluid transfer line sizes,with a powered fan,can very easily maintain the trans fluid temps in the 150F-170F range even under high stress performance application conditions

measure very carefully youll need to mount the transmission cooler in a location that allows clearance for both the cooler and its supply lines and in a location with easy access to outside air flow so the heated air can rapidly be replaced with cooler outside air, for effective heat reduction to the fluid to effectively take place.
ID suggest no smaller than AN#8 line (1/2") size and a 24000 lb weight rated cooler if you have the room to mount one on a serious race application, with a high stall speed torque converter.



keep in mind automatic transmissions tend to add a significant amount of heat to radiators that use the lower section to cool the transmission, adding a large efficient trans fluid cooler to the car can also significantly reduce the heat loads on the radiator

many guys don,t realize that adding an oil and/or a transmission fluid cooler, with its own fan and radiator that allows those liquids to be cooled separately, to your engine and drive train, significantly reduces the heat load on the radiator, and generally allows the engine temps to decline noticeably. in fact just adding a high volume oil pan and a transmission cooler can drop your engine coolant temps 20F-30F in many cases, Id also point out that theres generally 3-5 quarts in the transmission oil pan and an additional 5-6quarts in the converter and lines to the trans cooler


remote mounted oil filters can be used along with an oil cooler to to increase transmission cooler efficiency, and the remote filter and cooler used on a transmission also tends to increase fluid capacity ,and as a result the systems cooling efficiency as the longer the fluid remains in transit outside the trans dissipating its absorbed heat, the use of a auxiliary fan equipped fluid cooler on a performance transmission with a high stall speed converter tends to significantly increase its potential durability.

a rather common issue with adding oil coolers, is that many of the coolers available can significantly restrict fluid flow because of the small restrictive internal cross section of the internal tubing, AN #6 and 3/8" tube coolers can be quite restrictive, the AN#8 are better but DUAL AN#8 coolers and AN#10 lines generally work the best, and there's also frequently limited space to position a cooler in the outside cool air flow mandating a powered fans.
the solution to both issues can and frequently does require use of two different oil coolers but placed in series this can further increase flow restrictions, the solution is in use of larger internal cross sectional area,transfer lines and mounting the twin coolers in parallel thus doubling the effective cross sectional area reducing the flow restriction the cooler potentially could produce if used in series ... olers2.htm


viewtopic.php?f=80&t=10514&p=44478#p44478 ... ansmission



viewtopic.php?f=71&t=2817&p=7265&hilit=transmission+fluid#p7265 ... enance.htm


and go to a local NAPA and get a WIX trans fluid filter, as they are decent quality and cheap, and should be replaced at each fluid change Id also strongly suggest a magnet in the oil pan ... e=58904-EA


1994 CHEVROLET CORVETTE 5.7L 8-cyl Engine Code [P]
Engine Oil
Grade 1......API*[1]

Maximum Performance SAE 5W-30 Signature Series 100% Synthetic Motor Oil (ASLQT)

Performance Plus XL 5W-30 Synthetic Motor Oil (XLFQT)

Performance OE 5W30 Synthetic Motor Oil (OEFQT)
Above 0 F......10W-30
All TEMPS......5W-30
Manual Transmission,S6-40/ML9......GLS [2]
All TEMPS......
Synthetic Synchromesh Transmission Fluid (5W-30) (MTFQT)
Automatic Transmission,4L60-E......AF6 [3]
Signature Series Fuel-Efficient Synthetic Automatic Transmission Fluid (ATL) (ATLQT)
OE Fuel-Efficient Synthetic Automatic Transmission Fluid (OTLQT)
Standard Differential, Rear......GL-5
All TEMPS......80W-90
SEVERE GEAR 75W-90 Synthetic EP Lubricant (SVGQT)
75W-90 Synthetic Long Life Gear Lube (FGRQT)
SEVERE GEAR 75W-110 Synthetic EP Lubricant (SVTQT)
SAE 80W-90 Synthetic Gear Lube (AGLQT)
Limited Slip Differential, Rear......GL-5*
All TEMPS......80W-90 [4]
SAE 80W-90 Synthetic Gear Lube (AGLQT)
SEVERE GEAR 75W-90 Synthetic EP Lubricant (SVGQT)
75W-90 Synthetic Long Life Gear Lube (FGRQT)
SEVERE GEAR 75W-110 Synthetic EP Lubricant (SVTQT)
Brake Fluid......HB
AMSOIL Brake Fluid DOT-3 (BF3SN) [5]
Power Steering Fluid......PS
Power Steering Fluid (PSFCN) [6]
[1] Oil must be formulated to meet GM standard GM4718M.
[2] GM P/N 1052931.
[3] This specification has been updated from Dexron II or III to
Dexron VI per a Technical Service Bulletin from the
[4] Limited slip identification: tag under cover-attaching
bolt. Models with limited slip use 4 oz & 4.7 oz on 2007-08
XLR, 2006-08 Corvette Except Z06, 2006-08 Z06 6.8 oz
GM P/N 1052358 additive or equivalent when fluid is
[5] Hydraulic Brake Fluid, DOT 3 P/N 12377967, Spec. 9986121
[6] GM P/N 1052884, Spec 9985010
Oil Filter 25,000-Mile Ea Oil Filter (EAO23)
Oil Filter WIX 51036 Oil Filter
Transmission Filter WIX 58904 Trans Filter
6-8 Fittings, 0 Plugs..........LB
Synthetic Multi Purpose #2 (GLC3P)
Synthetic Water Resistant #2 (GWR3P)
DOMINATOR Synthetic Racing Grease NLGI#2 GC/LB (GRGCR)
Engine, with filter..........4.8 quarts [1]
Cooling System, Initial Fill..........14.8 quarts
AMSOIL Antifreeze and Engine Coolant
Automatic Transmission, 4L60-E Initial Fill..........5 quarts
Automatic Transmission, Total Fill
4 speed 4L60-E..........11.2 quarts

Manual Transmission, S6-40/ML9..........4.4 pints
Differential, Rear..........3.2 pints
[1] After refill check oil level.
Oil Drain Plug.....16 ft/lbs
Manual Transmission
Fill Plug 26 ft/lbs
Drain Plug 26 ft/lbs

If you simply are removing your transmission oil pan and replacing the transmission oil filter will replace approximately 5 quarts of the total of 11 quarts as the converter and other areas hold about 6 quarts , that won,t drain, so if you don,t intend to mix old trans fluid and new fluid youll need to fill and run and drain and refill or flush the torque converter.
First, normal operating temps, without adding an additional large effective trans fluid cooler can rise to be as high as 245F-250F, which can rapidly burn the clutches,

with a high stall speed converter,being installed, you need to find and install a more effective trans fluid cooler or youll find that higher average fluid temp will reduce the transmission life span noticeably, lots of guys ignore this and find that they eventually need to replace the transmission, they get it rebuilt, replaced and the new trans doesn,t hold up for the same reason the original trans failed...the trans fluid is too hot!
rather than find this out the way many guys do and pay for several transmissions its smarter to instal an effective trans fluid cooler with a fan, and AN# 8 lines to the cooler. have a trans shop flush the trans converter, lines and replace the filter at reasonable intervals and if you can YOU SUPPLY THE TRANS FLUID AND WATCH IT BE USED, so they don,t substitute far less expensive inferior transmission fluid.

be sure you accurately measure the available room in the location you plan to install an aux trans fluid cooler , get as large a cooler as you can fit in the car with a powered fan, because keeping the trans fluid down near 170F significantly extends trans life

if you race the car as the extra rpms and stress quickly build higher heat, which can quickly destroy the internal clutches in a transmission, depending on if you race auto cross etc. EVEN Normal driving, can result in 220F. This goes for any year and model c4 corvette with a torque converter clutch.
Transmission fluid hydraulically Transfers power within the torque converter, provides almost all the cooling to your transmission AND LUBRICATES.
keep in mind that all oil and transmission fluids breakdown over time,and heat increases the rate it degrades , The lubrication properties are critical to friction band, clutches,and bronze bushings within the transmission.
Remember that fluid does almost all of the work in the automatic transmission,and as it wears it should ideally be changed about every 30K-35K miles along with the filter,AT A MINIMUM, and IDEALLY ONCE A YEAR or every 15K if you drive the car hard! a trans shop will generally charge about $100 to flush out all 11 quarts and replace it with new trans fluid, the more frequently the fluids replaced the less crap builds up as flushing the trans with new fluid removes a significant percentage of metallic dust and built up varnish.
therefore, less chance that your will experience problems.

yes you can remove the transmission oil pan, replace the trans filter and replace both,the filter and fluid, then disconnect the trans fluid cooler line and allow the engine to run for a few seconds to pump remaining fluid out into a catch pan and refill the trans several times to do a D.I.Y. trans flush but theres a minimal chance if your not careful youll burn clutches if you let it run low on trans fluid, a trans shop pumps new fluid thru flushing out the oil fluid as the trans is flushed under constant pressure
DO NOT, use a generic brand of Dexron 3 ATF. These cheaper trans fluids are not the same quality as the better brands and just above Dexron 3 standards, and will not have the lubricity, or cleaning , or heat resistive additive packages to correctly work within your transmission for the life of the fluid.
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fitsp2.png ... nstall.htm ... _donts.asp


if the lines on the cooler look like this (below)

coolers with aux fans tend to be far more effective

you generally feed the fluid in the bottom and out the top line connection to prevent air trapped in the lines
naturally youll want to route all lines as far from headers as you can to prevent burns on the lines

Cooler Fittings
General Motors Ford Chrysler

GM Transmission Cooler Fittings

Powerglide - OEM
Fitting Location Thread Size Flow Direction
Upper â…›" Pipe Return/in
Lower â…›" Pipe Cooler feed/out

Powerglide - Dedenbear
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

TH200C Metric, 2004R
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Cooler feed/out
Lower ¼" Pipe Return/in

TH350, TH250
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

4L80E (1991-1996)
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

4L80E/4L85E (1997 & later)
Fitting Location Thread Size Flow Direction
Rear ¼" Pipe Return/in
Front ¼" Pipe Cooler feed/out

Ford Transmission Cooler Fittings

C3, C4, C5, C6
Fitting Location Thread Size Thread Size Flow Direction
Front ¼" Pipe Cooler feed/out
Rear ¼" Pipe Return/in

Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Cooler feed/out
Lower ¼" Pipe Return/in

Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

Fitting Location Thread Size Flow Direction
Front ¼" Pipe Cooler feed/out
Rear ¼" Pipe Return/in

Chrysler Transmission Cooler Fittings
All Torqueflite
Fitting Location Thread Size Flow Direction
Front â…›" Pipe Cooler feed/out
Rear â…›" Pipe Return/in

LOOK THIS OVER ... _Where.htm

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investing in a couple high heat tolerance magnets to place in any transmission oil pan certainly won,t hurt durability either
proper magnets trap metallic debris
SmCo Samarium Cobalt Disc Magnets

Samarium Cobalt MAGNETS HELP
magnets are ceramic and glass hard, don,t try to drill or grind them, as they can shatter
adding a deeper trans pan will generally improve the trans cooling a bit but it also tends to make ground clearance issues far more critical and damage more likely the use of an auxiliary fluid fan equipped cooler is generally far more effective. Id strongly suggest AN#8 or 1/2" NPT minimum fitting size and carefully measuring where youll install the fluid cooler well before ordering one and installing one thats large enough to easily handle the heat loads that may be required.
common mistakes are ordering a cooler to large to fit in available locations, or too small to do the job, and coolers with lines that are too small that restrict fluid flow rates


if your going to use a valve train cooling oil flow to cool the valve springs ,

you'll need to dissipate the heat that oil flow collects as it runs over the surface of those hot valve springs and a combination of a higher capacity baffled oil pan ,

and an auxiliary oil cooler to make transferring the absorbed heat load the oil carries away from the upper engine is almost 100% mandatory if your expecting the oil to cool the valve train for very long.
Id point out that you'll almost certainly want to use an oil cooler that's as large as you have room to effectively use and having a powered fan to increase air flow and heat transfer efficiency will help, bu remember the line size between the engine cooler and back to the engine will generally slightly restrict flow so, I,d advise at least a AN#8 or 1/2" internal cross sectional, size oil or hydraulic lines designed to handle 300F temps and pressure levels with a significant safety margin above what the engine produces, and having large remote mounted oil filter(s) won,t hurt either.
Yes they make dual transmission fluid and oil coolers so you might want to consider that option if you have an automatic transmission and Id sure suggest a fluid temp gauge that accurately measures transmission fluid and a separated gauge for oil temperatures.
IM currently using this transmission fluid cooler on my 1985 corvette but have used others in the past, and a dual cooler like this certainly has some advantages , if you need both oil and transmission fluid cooling.

a few links may help here

Gear Oil 101: Which Lube is Right for Your Manual Transmission?
Posted by OnAllCylinders Staff on November 10, 2017 at 9:00 am

Selecting the right gear oil or transmission fluid is critical to the life and performance of your manual transmission. (Image/Tremec)

Similar to what we discussed in our Automatic Transmission Fluid 101post, selecting the right gear oil for your manual transmission isn’t as easy as it might seem.

There are dozens of different types of gear oils, each with its own special designation and use, so we created this handy primer (oil pun!) to help you make good decisions.

Keep in mind that most modern manual transmissions have gear oil service intervals well north of 50,000 miles, with many being “lifetime” oils.

Driving enthusiasts, however, change gear oil to deliver improved transmission performance—like smoother shifting or added durability in extreme conditions. If this sounds like you, keep reading.

Gear oil, AKA gear lube, is often used in your manual transmission’s gearbox, and you’ll commonly find it in older transfer and differential cases too. But gear lube isn’t the only choice for a manual transmission. In fact, many modern manual transmissions actually spec for automatic transmission fluid instead of a traditional gear oil. Regardless of what your manual transmission uses, the fluid or oil’s primary function is lubrication—preventing metal-to-metal contact between the meshing gears.

Gear oil is different from engine oil.
For starters, gear oil can come in much higher viscosity ratings. In other words, a 80w-90 gear oil is much “thicker” than a 5w-30 engine oil.

But viscosity is only part of the equation. Here’s why:

Manual transmissions are often made up of different metals. The gears can be made of a hardened steel, while the transmission’s synchronizers (AKA syncros) are often made of a softer metal, like brass.

What’s good for one metal may adversely affect the other—so companies had to develop formulations that offered the requisite lubrication, yet wouldn’t harm any of the transmission’s components.

This is also where GL ratings come into play.

The most common ones you’ll see are GL-4 and GL-5. Those ratings basically reflect the oil’s ability to function effectively given different driving conditions (read: pressure between meshing gear teeth). GL-4 oils are typically found in most daily driven cars. while GL-5 oils are often reserved for high-stress, high performance applications like trucks and high-powered cars.

Your owner’s manual will tell you exactly what GL rating your transmission requires.

Sometimes you’ll see a bottle labeled MT-1. It’s intended for non-synchronized transmissions, like those found in heavy-duty commercial trucks, and certain four-wheel drive transfer cases.

You can find the gear oil’s viscosity and GL rating on its label. (Image/Summit Racing)

What about transaxles?
Though the role of the gear oil is the same, there are extra factors at play in a transaxle. That’s because transaxles function as both an axle and transmission. You can read more about transaxles and how they differ from transmissions here.

For instance, you might find different oil recommendations depending on whether the transaxle has a built-in limited-slip differential (LSD). In other words, seemingly identical cars may require different oil, depending on the presence of an optional LSD.

So, what should I use, then?
We could dedicate a dozen posts to the answer, but since this is a 101, here’s the simplest solution: Check your vehicle owner’s manual.

It will spell out exactly what oil you should use, complete with viscosity and GL values specific to your vehicle.

Bottom line: To avoid transmission damage, you must consider several factors (including viscosity and formulation) when selecting your gear oil.
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