more tranny Q and A's for Todd Erickson

[ssspoon@aol.com]

Hi Todd

Welcome to the group as a valuable source of knowledge, and thank you for the offer of your time to help us out. You recently provided advice about the fitment of specific 5 speed manual transmissions into a Turbo Legacy

I have a 92 Subaru Turbo Legacy for which I am having an engine blueprinted, and expect to develop 300 horsepower

I am searching for info on selecting a spare 4EAT auto trans to have upgraded to compliment my engine project

I have spoken with people with a preference for good later 4EAT over rebuilt/built-up 91-94 Legacy Turbo 4EAT

I have info that the Turbo Legacy trans has similarities and differences to that of the 4EAT trans in other Subarus

Would you discuss potential other Subaru models and model year transmissions which would be as good or better than the 92 Turbo Legacy 4EAT, and the fitment considerations similar to what you did for the 5MT please?

for example;
93 - 94 Turbo Legacy rather than 91 - 92 because all factory upgrades incorporated in 93MY

Thank you for any info you can provide

For those with further interest, here are comments/questions I sent to Colorado Component Rebuilders and their response

Auto Tranny Issue

Q: Possibility of getting my grubby hands on one from a 2002 WRX for my some-day-to-be 92 Turbo Legacy hot rod

A: This is not as good as the original Legacy Turbo tranny. It's made for a much lighter car.

Q: Also need to verify interchangeability of WRX auto trans with Turbo Legacy chassis and compatibility with Turbo Legacy TCU

A: Not sure about physical chassis, but the wiring and electronics are definitely different. Late '98 Subaru went from 4 bolt to 8 bolt bell housing. The lower bolt on the starter has no place to bolt to. You'd have to do some modifications to address this.

Q: Trans is designated 4EAT but like EJ22 there's more than one version. Have even seen info 4EAT also used by Nissan Pathfinder and Mazda MPV

A: They're basically the same transmission, but they are different gear ratios, and the torque converter is different because it bolts up to a different design of flex plate.

Q: Subaru service bulletins show 4EAT used by SVX, Legacy, and Impreza

A: 4EAT simply means 4 speed electronic automatic transmission.

Q: Turbo Legacy auto trans is often said to be the same as used in SVX

A: Yes, but, the SVX had two different gear ratios...3.9 and 3.545. The torque converter for the 3.545 won't fit the Legacy Turbo flexplate. (Turbo Legacy is 3.90)

Q: 91 Model Year Update Course shows turbo 4EAT torque converter size increased for additional strength over the N/A 4EAT.

A: Size was different due to different gear ratio. The internals are identical for the SU12 and SU13.


The 91 Model Year Update Course gives the following tranny info to consider;

In order to handle the increased torque produced by the turbocharged engine, the 4EAT Transmission uses a larger Torque Converter. For additional strength, the input shaft has also been shotpeened. In both the Forward Clutch assembly and the High Clutch assembly, the number of drive and driven plates has been increased by one (1), while the retaining plate thickness has been reduced. The Low/Reverse Brake assembly has increased the number of plates by two (2), but the thickness has been reduced. The outer diameter of the Servo piston (band application) assembly has been increased in order to provide more band clamping force. Of course, the servo piston seals have also been enlarged to match the servo piston diameter. Due to the new piston shape the number of "O" ring seals has been reduced by one (1) Lubrication passages have been added to the Planetary Carrier assembly for increased gear durability. Finally the logic in the Transmission Control Unit (TCU) has
The SVX crowd is much more into the auto trans biz than the Legacy crowd. Probably cause that's all the factory gave them. Those interested in further info on factory mods and upgrades to the SVX 4EAT trans (with some Turbo Legacy applicability) should check out the following:

http://my.voyager.net/~tmclane/#_Toc482082574 The Subaru SVX FAQ

http://www.drwtransmission.com/subaru_svx.htm DRW Transmission

http://www.subarusvx.com/faq/transmission.html SubaruSVX.Com Trans FAQ

Above sites also recommend the following;

http://www.txchange.com/transgo.htm TransGo Performance <http://www.transgo.com/> (626/443-7456) "Shift Improver" kit (part # SKRE4R01A). This $50 kit has 4 plastic rings for the transmission that are designed to handle greater temperatures than stock Subaru parts. 1988up 4 speed with or without lockup Corrects/Prevents/Reduces: Planetary burnup; 3rd clutch failure; forward clutch burnup Soft 1-2 shift; 2-3 cutloose; Band burnout and low lube flow causing overheating and total burnup

If anyone else found this info interesting or have something to add please let me know

Larry Witherspoon

ssspoon@aol.com

[Josh Colombo]

Larry,

I'm pretty sure I have that shift kit from Transgo in my car. A Friend of my mom own's a tranny shop. He did a rebuild on the valve body last summer. It wasn't a cure all for my tranny problems, however it did help things a little. The 1-2 shift is very firm now. He didn't do the entire kit, just the valve body. I can double check your numbers to the box I got at home.

Josh