4EAT TCM interchangeability

[bridorf]

Just wondering if anyone has a list of changes in the Transmission Control Units and how using one from a different car would effect the recipeint?

 

I have a 1993 Legacy L AWD Wagon with a bad TCU, and found one from another 1993 (slightly later production date) Legacy L AWD with a TCU that ends in 031 instead of 011. Any knowledge of what changes were made from one control unit to another?

[idosubaru]

someone mentioned in one of my threads that switching between "sedan" and "wagon" made an annoying difference - still worked but had different shift points and wanted to hang in 3rd sometimes when it shouldn't. he speculated it was the wagon/sedan difference. you can search for my EJ TCU thread to read more about it.

 

any 90-94 TCU should "work".

[johnceggleston]

there are 2 apparent differences between the 95 sedan and the 96 wagon TCUs.

1. the mounts are different.

2. the lable on the main 'chip' is different.

 

the circuit boards are identical except for the main chip label. i believe this refers to the programing. the 96 wagon TCU in the 95 sedan (with the 96 4eat) was slow to shift up, liked to stay in 3rd. i don't know the engineering, but my ill-logic tells me the weight difference may be at least part of the reason.

 

obviously a 97 GT tcu will operate differently than a 97 OBW, both cars have the 2.5L w/ 4.44 final drive. the GT TCU in the OBW will try to drive it like a GT. this may not be drsireable. i haven't tried this yet, but i will this spring. and vice versa.

 

 

i know you won't blow anything up by swapping, but how it drives may be a little off. my guess is that sedan to sedan or wagon to wagon will be ok. i think some of the early legacys had different final drives for different years which may make a slight difference in driving. check here :

 

http://bbs.legacycentral.org/viewtopic.php?t=13500&sid=7add370daf15909c801cba58%20f69c2cbd

 

 

and someone else has posted that they are all interchangeable.....so who knows.

if you do try it, let us know.

 

edit: i just re-read the original post, it could be LHD vs. RHD. go to www.car-part.com and search for ''computer box not engine'', then transmission and see what part numbers you come up with.

there are 4 to choose from,

 

FWD ( 93 & 94 same) = ...AC021 & ...AC600

LHD ( 93 & 94 same) = ...AC031 & ...AC610

LHD turbo ( 93 & 94 same) = ....AC051.

RHD = ?

 

you may have to look through several pages to find a listing with a part number, but eventually you will. look at other years until you find the TCU you're thinking of buying.

 

this search process may dis prove my sedan to wagon being a bad swap since the interchage does not reference body style, just year, AWD vs FWD and LHD vs. RHD vs. TURBO.

[idosubaru]

I just swapped a 1995 FWD transmission from an EJ22 into a 1997 Legacy that was originally equipped with an EJ25 and 4.44 gear ratio AWD automatic....and the test drive was stellar, but only a few miles. shifted fine...but i didn't hit any hills or do any freeway driving either.

 

1995 FWD EJ22 swapped into a 97 AWD 4.44 (originally an EJ25) Legacy sedan...not sure what the transmission came out of unfortunately but the TCU seems to operate it just fine.

[bridorf]

The 031 unit I pulled out of a MY 1993, early 1993 production date, Legacy L AWD Wagon (same exact set up as my car per buttons on shifter, etc...) My MY 1993 Legacy L AWD Wagon, but late 1992 production date, car has a TCU ending in 011. Just thought someone might have a database of what changes to the car included an update to the control unit requiring a part # change?

[idosubaru]

slap that baby in there - all 90-94's should interchange just fine and with yours being the exact same car, sounds like a no-brainer to me.

 

unfortunately databases like you're looking for are non-existent. transmission interchange questions come up all the time and there's rarely a definitive answer, often people just say "get the exact same transmission" to be sure, that's the only sure way.

[johnceggleston]

The 031 unit I pulled out of a MY 1993, early 1993 production date, Legacy L AWD Wagon (same exact set up as my car per buttons on shifter, etc...) My MY 1993 Legacy L AWD Wagon, but late 1992 production date, car has a TCU ending in 011. Just thought someone might have a database of what changes to the car included an update to the control unit requiring a part # change?

 

 

from https://www.subarugenuineparts.com/oe_parts_cat.html

 

 

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Part number 31711AC011 was superseded by part number 31711AC031.

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