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F4A33 & W4A33 Transmission Information

Transmission Codes

The codes stamped on the top of the transmission bell housing do actually mean something. These do pertain the manual transmissions to. Here is what the code means.

Code Meaning
W F=Front Wheel Drive, W=All Wheel Drive
4 4=4 Speed, 5=5 Speed
A A=Automatic, M=Manual
33 Transmission Series, Relative Torque capacity
1 Version, Based on major design changes
UQ61 Transmission type, This is what tells you what the vehicle it came out of

What transmission do i have?

Now you know what the code means the next question is usually what transmission do i have or what transmission do i need to look for? Most of this information was pulled from Mitsubishi CAPS.

Code Car
F4A33-1-UPQ 95-99 D32A DSM
F4A33-K-1UPQ 95-99 D32A DSM
W4A33-1-UPQ 95-99 D33A DSM
W4A33-1-UPQ2 95-96 D33A DSM
W4A33-1-FNQ 96-99 D33A DSM
W4A33-1-NPZT 95-99 D33A DSM
F4A33-1-UP63 92-94 D22A DSM
W4A33-1-UP6 91-92 D27A DSM
W4A33-1-UQ6 1989-1990 E39A GVR4
W4A33-1-UQ62 1991-1992 E39A GVR4
W4A33-1-UQ63 1992-1994 D27A DSM
W4A33-1-UQ61 1990-1992 D27A DSM
W4A33-1-FP6 RVR
W4A33-1-FM6 RVR


Transmission gear ratios are not all the same for the automatics.

Transmission First Second Third Fourth Reverse Final Drive
F4A33 2.551 1.488 1.000 0.685 2.176 4.376
W4A33 2.551 1.488 1.000 0.685 2.176 4.422

If you want to see RPM vs MPH charting then see Main article: RPM vs Speed Charting

Gear Set

The 96/97 split also transferred to the automatic transmissions as well. This is to determine which gear set the transmission has so you can identify the trans as well as which transfer case you need to have. Just remove the front diff cover by removing the 10mm bolts on the rear of the transmission on the backside of the case, rotate and count teeth. You don't have to fully remove the differential to count this. I put small pieces of tape to hold my place and also put a piece of tape every 10 teeth to help keep track. RVRs are 97-99 gear set. To check this against your transfer case then see Here: Transfer Case Ratios

Gearset Front Diff Teeth
91-96 72 Teeth
97-99 71 Teeth



Pulse Generators


Shift Solenoids

In these transmissions only the forward gears are controlled by solenoids. Park, Reverse, and Neutral are all controlled mechanically via the shift selector. There are only 2 shifting solenoids on the valvebody. On all transmissions you will always have a 3rd solenoid. This is the line pressure control solenoid that controls the line pressure. On 2g transmissions you will have a 4th solenoid and this is the control solenoid for TCC lockup. Here is a chart that illustrates what solenoids are used for what gears. You will notice that since only 2 solenoids are present that there is only 4 possible solenoid states. When both solenoids are off that is 3rd gear. This is a safety feature so if the transmission happens to loose all power you still have Park, Reverse, Neutral, and 3rd to get the car to a safe place.

Gear SOL-A (Yellow) SOL-B (Orange)
First (L) On On
Second (2) Off On
Third (D) Off Off
Fourth (OD) On Off

Transmission Pump

This is the pump for the fluid circuit. This is the heart of the transmission. The 1G and 2G pumps are discontinued. The part number is MD735138. Here is a great video on transmission pump tips from John @ Import Performance Transmissions.

Video: Click

Transmission Pan

The pan works on both 1g and 2g transmissions. The flange is the same on the transmissions.

Transmission Filter & Gasket

w4a33.com_images_filtergasket.jpg The transmission Filter and gasket are the same for either of the transmissions. If your looking for a cheaper option then you need to get a filter that has two inlets like whats circled in the images. The part number of ones that will work is the Rock Auto PIONEER 745062 and NAPA ATP 19260.

Pan Gasket MD739243
Filter MD735572

Line Pressure

The DSM auto trans is a stout piece, but everything has its limits and anything can be broken if you try hard enough. The first limit is pressure application during shifts. Shifting with any of the full-manual methods like the Kiggly Blue Wire Mod wiring or a aftermarket TCU will fix this and have shifts occur at full line pressure. When shifted at full line pressure, a stock trans will live a decent life down into the 10's. A trans with a 5-friction front clutch and translab shift kit with the pressures cranked will live down into the high 8's or so. Anything quicker than this starts needing pressures cranked up higher. Kiggly has run over 300psi without problems, although he doesn't recommend much over 200psi for any mixed street plus racing usage.1)

Transfer Gears

Inspect yours every 20 passes or so in a high power setup. The gears should also be shot peened, Kiggly has TRE do this. If you're in the low 1.3's or so, even more frequent inspection intervals are a good idea. There is no excuse not to inspect the center diff gear in an AWD car, it is just 6 bolts to pull the cover, drain the fluid, and remove and inspect that center diff gear. The inboard side of the gear (diff housing side) is where I've seen cracking start in every single failure. Look at the roots of each gear tooth for cracks and replace all three of the drive gears if you find any cracks. The center diff gear or this corresponding gear in the FWD always cracks first, but the rest are very soon to follow. If the drive gears break, it tends to explode the case and make a gigantic, dangerous, and expensive mess.2)

End Clutch

Here is a video of John @ Import Performance Transmission doing a end clutch rebuild. This will be far superior then text explaining it so ill just let you watch this instead.

Video: Click


Main article: Transmission Valve Body


RD Port mod

The RD Port Mod oils the planetaries and helps cool them to prevent them from burning up as easily.

Video: Click

Shift Selector

morrisonfabrications.com_wp-content_uploads_2018_06_light-box.jpg Morrison Fabrications is making a low profile shift selector and shifter cable bracket for the automatic transmissions. The 3“ tall factory shift lever on the transmission was reverse engineered into a lower profile ~1” lever along with its own cable bracket in order to maintain geometry and factory motion ratios. This gives more room for intercooler piping, moving the assembly as far down and away as possible.

Fits 1g/2g FWD and AWD. At the time of this writing they are close to releasing a version for those who use Ratchet Shifters.

Shift Kit

w4a33.com_images_shiftkit.jpg If you are rebuilding your Transmission and have not done a shift kit then you should. These prolong your transmission by increasing pressures and using different springs and balls in the valve body to firm the shifts up. Less slip means longer life. The shift kit needed is Translab STL-175-HP. This shift kit works on both the W4A33 and the F4A33 transmissions. Per Translab the shift kit Corrects or prevents 2-3 shift flair, coasting downshift clunks, long soft slide shifts, part throttle 3-2 shift bang, slide 1-2 shift, and 3rd gear takeoffs. These shift kits usually go for around $65. Whenever you install a shift kit it is always a good idea to replace the main valve body separator plate which some of the holes wear from check balls. This is also an indicator along with having steel check balls as shift kits come with torlon check balls. The part number for that is MD735689. If you for some reason need the small separator plate that part number is MD735934. Here is a 4 part series from John @ Import Performance Transmission installing a shift kit.

Part 1: Click

Part 2: Click

Part 3: Click

Part 4: Click

Shift Kit Advanced

There are some additional mods that Kiggly Racing has brought to light. They are all outlined in his presentation that he did at the shootout in 2014 and 2015. You can download that pdf on the Downloads page. What he outlines in this presentation is 2 main things. One of them is removing 2 of the .070“ frictions and adding 2 of the .037 steels to fill the gap for a total of 4 steels. Only in use as the primary clutch when in Reverse. It spins freely in 2nd and 3rd gears. The benefit of this is that it reduces drag. One other thing he does is put a plug in the separator plate and drill out a .067 hole in the plug and also clearances the valvebody for the plug. This is the band apply port. When doing this mod it will minimize 1-2 shift binding and is less abusive to rear clutch splines. There are illustrations in the PDF on the Downloads page.

Rebuild kit

People commonly ask what rebuild kit they should get. There are a ton out there but it seems the recommended one to get is the one from TRANStar or the Alto Red Eagle Kit. Here is the W4A33/F4A33 sections of their catalogs.

Transtar Book Click pg 275-294

Alto PDF Click


Coming Soon

Front Clutch

w4a33.com_images_endclutch.jpg There are 3 options for front clutch kits. All of them are made by Kiggly Racing. These are also something you should do to help prolong performance and reliability in the transmission. The 5 friction doesnt hold as much as the 6 friction just as the 6 friction doesnt hold as much as the Billet. The 5 friction is good for stock rebuilds to to performance street duty. The 6 friction is the next level up and is idea for street/strip use. The Billet end clutch kit is ideal for street/strip to full drag car.

Front Clutch Kit Torque Capacity
OEM replacement 5 Friction 25% increase in 3rd
OEM replacement 6 Friction 50% increase in 3rd
Billet Basket & Clutches 247% increase in 3rd

Transfer Gears

w4a33.com_images_transfergears.jpg These are gears that transfer the power in the transmission. Stock these gears are prone to cracking if pushed to hard. The bad thing is when these crack they take out the case, and have even locked up the drive train. You can do things to the stock transfer gears to help prolong longevity like running a quality transmission fluid and/or having them shotpeened and REM Isotropic finished. The stock gears are usually a ticking time bomb and carry a serious potential safety warning. If your transmission has stock gears but it whines like it has straight cut gears then your transfer gears are cracked. If you truly want a long lasting and good performing transmission these are really important. If you plan to launch your car occasionally or more then these are heavily recommended. In fact most of the failures come from stalling the car for a launch because your trying to hold so much torque back. If you are upgrading the brakes to hold the car back then that is a good indicator that you need billet straight cut transfer gears as its guaranteed that it will break the OEM transfer gears sooner or later. Also remember helical cut gears are designed to reduce noise. As a byproduct of reducing noise it heavily promoted deflection. The Billet straight cut transfer gears are a product of JB Designs. They offer these in Standard and 7% overdrive. Get standards unless you have either 800+ HP or have a stroker in which you should get the 7%.

Input Shaft

w4a33.com_images_inputshaft.jpg This is a 300m input shaft. This is another product of JB Designs. These are for transmissions that came with lockup only as the shaft is different. So it will not work in a 1G transmission. The stock shafts are pretty tough but once you start getting under mid 8 second passes you should seriously consider this as an upgrade as the stock one the splines start twisting.

Front Diff

w4a33.com_images_frontdiff.jpg The front diff has a few options as well as aftermarket parts. The aftermarket parts consist of the pictured Kiggly Racing Diff Saddle. This prevents deflection in the diff. If anything happens to the diff gear then its going to also take out your transfer gears and the transmission. Some have run the stock ones down into the 7s in AWD cars but this product is more geared towards FWD cars running big slicks. However its relatively inexpensive and is good insurance. Another aftermarket part is the RIP GRIP diff insert. This is also a JB Designs product and it acts as a locker when you need it to but will unlock when cornering. This is basically a part to act like a welded diff on straights but unlocks when maneuvering so the drive train doesn't bind up. You can also replace it all with a Quaife. However Quaife differentials in these cars are not recommended for high HP applications. They are more oriented towards auto cross or road course duty. The last option is the weld the diff. This works very effectively but you also will have drivetrain bindup issues when trying to turn. If you have ever driven a car with a spooled/locked/welded front diff then you already know what i mean. Most the cars running 7s are running stock front diffs or stock front diffs with the RIP GRIP insert.

If you are curious as to if the insert is what you should buy then you can go by this rule: If you plan to street drive the car at all then do not use one. If you plan to just track your car but dont want a welded front diff so you can turn at the end of the track then this is the product for you. Street driving with the diff insert can cause excessive wear on the part.

Center Diff(AWD Only)

The center diff leaves you with 3 options. One is to run the stock center diff and viscous coupling. Trying to apply more then 500HP through this will usually net you with the front wheels spinning and the rears not. This can wear out a differential quick and cause failure. The next option is a Quaife center diff. This option like the Quaife Front Diff is more geared towards street, autocross, and road coarse duty. They dont do well in high power output drag scenarios and will do what the stock diff does just to a lesser degree. The benefit of the part really isnt worth its $1200 price tag. The best option for high power drag racing is going to be to have the center diff welded. When you weld the center diff in these you take the Viscous Coupling out and eliminate it from the transmission altogether and pulls alot of weight out of the transmission. This does have negative effects on turning radius but its not to bad and is the best option. If you weld your diff make sure you clean it extremely well and keep it at a high temp while welding and dont let it cool off. Once its all welded up people usually bury it in a bucket full of cat litter so it slowly cools down over time instead of rapidly. This is the prevent warping. You also want no weld splatter because those can come off in the transmission and go through it. If your having it done take it to a professional welded and make sure they know how to do this properly. Most anyone that does drivetrain rebuilding specific to these cars know how to do it right.

Rear Drum

The rear drum is called that because it is at what would be the rear of the stack. It is commonly referred to as a forward drum as all of the forward gears utilize this. If you are making serious power then this is a good idea. Also it prolongs the performance and the longevity of the transmission. This is compatible with the stock input shaft. This is also a JB Designs product that comes loaded with the friction/steel stack. It is tried and true on many 7 second setups with 100% of them reporting extremely positive results. w4a33.com_images_forwarddrum.jpg

Transmission Pan

An aftermarket transmission pan brings increased capacity and being aluminum it does assist in cooling. It is also shaped in a way to aid in fluid collection and diverting it to the pickup. The fluid drain plug is also relocated to the lowest point in the pan. JB Designs makes these pans for both 1G and 2G and they come with new filter and gasket. w4a33.com_images_transpan.jpg

transmission.txt · Last modified: 2023/07/09 23:48 by admin