October 22, 2021

AT Transmission Tips and FAQs

AT Transmission Fluid Recommendation:


The fluid is the “blood” of the transmission. There are many different well designed ATF fluids out there that work great in our cars. Pretty much any synthetic ATF will be sufficient. A lot of guys like to use RedLine, Amsoil, Royal Purple, etc. The factory ATF fluid is called Mitsubishi Diamond Star ATF, but I don’t know if or where you can get it these days.



Where to Drain the Fluid:

Placement of the Drain Bolt

The picture shows the plugs to remove and drain the old fluid. It is recommended to do this every 30K miles along with the filter. It would be good practice to change it around 20K or you are already working with the transmission. Remove the two plugs and let it drain. The one on the pan is 17mm and the other is 24mm (I think).


The capacity is about 5 to 8 Quarts after draining pan and diff. It’s better to buy extra and be safe. Start with 5 Quarts and then check the levels accordingly, which is discussed below.



Filter Information and Removing the Pan:

2G DSM Auto Transmission Pan

As mentioned above it is recommended to change the filter regularly. The reason is the transmission relies on fluid and pressure to function correctly. A dirty filter can clog up and kill the performance. Check your shop manuals for the torque specifications first!


The filter will come in a kit. It has a neoprene gasket (black rubber). The neoprene gasket requires precise torque (86-106 in. lbs.) applied to the pan bolts (10mm) or it will pull the gasket and/or damage it. It will leak if this happens. Some have found using the fiber gaskets helps.


Make sure the screws that hold the filter to the valve body are the right length. This is VERY Important. The filter MUST seal against the valve body.


* If you want to go back into the pan and change the shift adjuster, you will most likely ruin the gasket so grab and extra if you are doing a shift kit install.



To remove the pan, remove the 14 (10mm) bolts that hold it up. Drop the pan. You may need to lightly tap it with a rubber mallet to break the gasket free. DO NOT pry with a screwdriver as you could damage the area where it seals.


To seal the, simply use a thin layer of RTV. Apply on both sides of the gasket. Install pan and let it set for a few hours to dry before adding fluid. Once finished, it is a good idea to check for leaks after driving as well as making sure the pan bolts are still tight.


How to check the Transmission Fluid:


Warm the car to normal operating temp (drive it). Take shifter (e-brake on, so you don’t move around during this and on level ground) and run the shifter slowly through the gears. P-R-N-3-2-1-2-3-N. Clean the dipstick off and put it back in. Then after a few seconds, pull the dipstick again while the transmission is in reverse.


It should be at the “hot” mark (line on dipstick) when car is good and hot (again, at normal operating temp). The cold mark is not a good and accurate test due to fluid expansion. By checking the fluid while hot, you are getting the fluid to the highest level possible. This alleviates all guessing.


If you have too much fluid in the transmission (overfilled),you will know once it gets hot as it usually spews out of the dipstick. This creates a mess of may cause smoke, or even a fire.


The capacity is about 5 to 8 quarts after draining pan and diff. If you overfill it, simply drain some out until you have the correct amount in.


Types of Transmissions and Transmission Codes:


3000 GT 91-99 4 SPEED FWD V6 3.0L F4A33-1

DIAMANTE 92-96 4 SPEED FWD V6 3.0L F4A33-1

DIAMANTE 97-01 4 SPEED FWD V6 3.0L 3.5L F4A51

ECLIPSE 90-94 4 SPEED FWD L4 1.8/2.0L KM175-5/F4A22-1

ECLIPSE 91-98 4 SPEED FWD Turbo L4 2.0L F4A33-1

ECLIPSE 95-98 4 SPEED FWD L4 2.0L 41TE (A604)

ECLIPSE 96-98 4 SPEED FWD L4 2.4L F4A23

ECLIPSE 91-98 4 SPEED AWD Turbo L4 2.0L W4A33-1

ECLIPSE 96-01 4 SPEED FWD L4 2.4L F4A42

ECLIPSE 96-01 4 SPEED FWD V6 3.0L F4A51

GALANT 85-88 4 SPEED FWD L4 2.4L KM175-1

GALANT 89-93 4 SPEED FWD L4 2.0L KM175-5/F4A22-2

GALANT 91-92 4 SPEED AWD Turbo L4 2.0L W4A32-1

GALANT 94 4 SPEED FWD L4 2.4L F4A33-1

GALANT 94-98 4 SPEED FWD L4 2.4L KM177-8/F4A23-2

GALANT 95-98 4 SPEED FWD V6 2.5L 41TE (A604)

GALANT 99-01 4 SPEED FWD L4 2.4L F4A42

GALANT 99-01 4 SPEED FWD V6 3.0L F4A51

GALANT SIGMA 87-5/88 4 SPEED FWD V6 3.0L KM177-0

GALANT SIGMA 5/88-91 4 SPEED FWD V6 3.0L KM177-8/F4A23-1

ECLIPSE/LASER/TALON 90-94 4 SPEED FWD L4 1.8L-2.0L KM175-5/F4A22-2



TALON/ECLIPSE 95-98 4 SPEED FWD L4 2.0L-V6 2.5L A604

STEALTH 91-96 4 SPEED FWD V6 3.0L F4A33-1

2000 GTX 92-94 AWD 2.0L W4A32

EXPO/LRV 92-94 AWD 2.4L W4A32

COLT/VISTA 92-94 AWD 2.4L W4A32


Proper Automatic Transmission Care: Recommendations of John, the owner of Import Performance Transmissions


1) Check your fluid level regularly- although fairly obvious, many people neglect to do this- or do this wrong. Consult the vehicle’s owner’s manual if you are unsure as to how to do this correctly, as it can vary between different vehicles. If you need to add fluid, it is always indicative of a leak. Unlike motor oil, your transmission fluid level can only go down if you are losing it somehow.


2) Service your transmission regularly- transmission fluid breaks down in the same way that motor oil does, but this is a step in preventive maintenance that is often ignored. I’ve rebuilt countless transmissions over the years that clearly were never properly maintained- many of them had never had a single fluid and filter change. Many manufacturers have different recommendations on the service intervals, but I recommend that this be done once a year or every 15- 20,000 miles.


3) Install an external transmission cooler- you’ve all heard the cliché that heat is the number one cause of transmission failure, well it’s true. A reduction of 40 degrees in your transmission fluid temperature can double the life of the unit. When shopping for a cooler, a stacked plate design is far superior to a “tube and fin” type. If you’re going to go through the trouble of installing one, you may as well put on the best kind. On this same subject, it is also always a good idea to insure that your vehicle’s cooling system is in optimum condition- most automatics utilize a fluid to antifreeze heat exchanger that is built into the radiator.


4) Install a transmission temperature gauge- with a gauge you will be able to tell when your trans is getting hot before it’s too late.


5) Add a friction modifier- there are a few excellent products that can be added to your automatic trans that will significantly increase the life of the transmission. I recommend the products that are made by LubeGard. On the same subject, avoid at all costs the auto parts store “mechanic in a can” and “stop leak” type products- they are mostly seal swelling agents and will usually harm the trans rather than help it.


6) Install an in-line cooler filter- most automatics have some type of filter, however, there is always room for improvement. Factory filters vary in effectiveness; many transmissions use something that isn’t much better than pouring the fluid through a screen door. The idea is to eliminate contaminants such as small metal particles and loose debris as effectively as possible. In line filters are inexpensive, easy to install, and are highly effective in removing damaging contaminants from the transmission fluid. I recommend the ones made by Magnafine and Filtran- in addition to their filter element, both of these products have a bypass valve in case they become clogged and also an internal magnet to further aid in trapping ferrous debris.


7) Use a synthetic based fluid- automatic transmission fluid serves many functions. It provides cooling and lubrication, it is the hydraulic fluid that applies the clutches and bands, and it even “drives” the car through the fluidic coupling that occurs in the torque converter. It stands to reason that a synthetic fluid is much less susceptible to breakdown, a better lubricant, reduces friction and also has the capability of reducing operating temperatures. More importantly, in cases of extreme cold and extreme heat, fluid made with a synthetic base stock is much more stable from a viscosity standpoint. If you don’t believe me, try to pour “dinosaur” oil out of a container at -10 Fahrenheit- it’s not exactly going to serve very well as a lubricant when it’s the consistency of Jell-O.


8) Check transmission problems promptly- most transmission problems start out small and will get worse over time. Often times, major repairs can be avoided by taking care of a problem early on. If you see a warning light on the dash, see a few drops of fluid in the driveway or even just have a feeling that something isn’t quite right, there is no better time than the present to get it checked out.


9) Install a shift kit or modified valve body- while normally thought of as a “high performance” modification, almost any vehicle will benefit from shortening the shift time, reducing overlap and “cleaning up” the shift quality. This in turn reduces heat and also reduces wear on the clutches and bands. Many of these modifications also address certain factory design shortcomings and eliminate common drivability complaints. Most of the better engineered products have shift quality settings that are adjustable to achieve a result that is appropriate for the intended usage. The person with an 11 second rocket will have different needs than the person who occasionally tows a trailer with his SUV.