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4EAT control unit compatibility


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This is kind of an off-the-wall question, but I figure somebody here must know.

 

I've got a 92 legacy with a 4EAT tranny, which I really like. However, I briefly owned an 02 Impreza, and its 4EAT has shifting characteristics that I liked a lot better. Primarily, it was much more eager to lock up the torque converter, which improves efficiency and reduces transmission temperatures. So, I got to wondering if would be possible to get a TCU computer from a newer subaru (sometime in the early 2000's) and swap it in to my 92 legacy with no other modifications to the tranny or the wiring harness (I suppose I could switch a few wires around, but I don't want to have to swap the whole wiring harness or anything of that nature).

 

I know it's probably a long shot, but subaru has done some weird things, so I thought I should check.

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This is kind of an off-the-wall question, but I figure somebody here must know.

 

I've got a 92 legacy with a 4EAT tranny, which I really like. However, I briefly owned an 02 Impreza, and its 4EAT has shifting characteristics that I liked a lot better. Primarily, it was much more eager to lock up the torque converter, which improves efficiency and reduces transmission temperatures. So, I got to wondering if would be possible to get a TCU computer from a newer subaru (sometime in the early 2000's) and swap it in to my 92 legacy with no other modifications to the tranny or the wiring harness (I suppose I could switch a few wires around, but I don't want to have to swap the whole wiring harness or anything of that nature).

 

I know it's probably a long shot, but subaru has done some weird things, so I thought I should check.

 

no.

Newer TCU's communicate with the ECU to make for softer shifting (playing with the timing etc). The 92 doesnt do that, or at least not the same way. It may also talk to the ABS (not sure).

if you look at a pre 95 diagram to a post 95 diagram, in the post the TCU talks to to the MPFI controller.

It may not function properly. Also i dont even think you can get it to plug in.

 

I dont think youll hurt anything besides the tcu by trying. Also your tranny may not be beefy enough for the extra torque load.

 

nipper

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Thanks for the reply!

 

if you look at a pre 95 diagram to a post 95 diagram, in the post the TCU talks to to the MPFI controller.

 

Yeah, that would pretty much do this:Flame: to the swapability. It really is amazing how much stuff changed on these cars when they went to OBDII. I suppose I could swap harnesses and ECMs, but I'd rather not get into that:rolleyes: . Not to mention adding a second oxygen sensor, and...

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I've got a 92 legacy with a 4EAT tranny, which I really like. However, I briefly owned an 02 Impreza, and its 4EAT has shifting characteristics that I liked a lot better.[...]

While the Phase-I (pre-99) and Phase-II 4EATs share certain characteristics, they also have many differences. This article explains a lot of that: http://endwrench.com/images/pdfs/4EAatPh2Win04.pdf

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