Transmission swap done.. but have problems..help

[subaruman]

I have a 1990 Legacy L with a bad AWD automatic tranny. So I found a 95 Legacy LSI donor car. The donor cars transmission was flawless. No torque bind, shifted fine, etc... I confirmed the final drive ratio for the two years to both be 4.11. So I installed the transmission into my 90.

Started it up, runs, shifts good, but I'm having rear end problems. Any slight corner the rear end binds. If I floor it on the grass in a straight line the rear end will chatter. I installed the FWD fuse and it stays in AWD, and the symptoms persist. So I thought maybe the computer was different. I put the 95 computer into the 90... that made it worse and won't shift out of 1st. Maybe there is a separate control module I don't know of that needs to be swapped.

I thought maybe the rear ratio was wrong so I swapped in a 3.9 just for the heck of it. That was even worse.

So I'm at a loss. I'm growing tired of working on this thing. Any help would be much appreciated!

Thanks
Jeremy

[cjc]

did you change out the ecu or the tcu from he donor?

[subaruman]

did you change out the ecu or the tcu from he donor?

Yes I tried the TPS from the doner. It was not compatable. The tranny would not shift at all with the 95 TCU.

I swapped back in the 4.11 diff and I have just learned to live with the torque bind.

Thanks,
Jeremy

[jedz123]

does it clunk? My Impreza did the same thing when I changed the tires to 15"

Any slight corner the rear end binds. If I floor it on the grass in a straight line the rear end will chatter.

so maybe it's a simple as tires... I know the TCUs are different through the years same with the ECUs (OBD1 to OBD2) so there might be a communication problem between the two (ECU and TCU). Thats Probably why (I Hypothesize) that the FWD fuse won't engage FWD. (No Offense) If I were you I would have looked for a tranny from the same generation or at least no latter then 94 (95 being the first year of OBD2). Any way I hope to be some help.
GOOD LUCK!
~Justin

[subaruman]

Yeah I know, next time I will grab a tranny from the same year. But the one I swapped in I got for free so I figured I would give it a shot.

Interesting you bring up the tire upgrade problem. I put on 15" wheels on it... i'll swap the 14's back on to see if the problem goes away.

What is kinda weird is the FWD worked the other day with the fuse.... but then stopped working the next day. Eh... so I dunno maybe my TCU is fried.

Thanks for the ideas
Jeremy

[vrg3]

I don't think it has anything to do with electronics. I think your new transmission is suffering from torque bind. There's an article in the Legacy Central Library about it.

[subaruman]

I don't think it has anything to do with electronics. I think your new transmission is suffering from torque bind. There's an article in the Legacy Central Library about it.

Yes, I'm familiar with torque bind. But when the transmission was pulled from the donor car it had no binding.

[vrg3]

I know; I read your first post, but I still don't think it's electronics.

[subaruman]

Finally a conclusion to this problem. After a few months of trouble shooting I found that my TCM was shot. Found a new used one at the junk yard.. popped it in and torque bind is gone! Thanks for everyone’s help with this problem.

~Jeremy

[Subaru for Life]

Congrats and thanks for the update .

[AWD_addict]

Interesting. What model year was the working TCM from?

[subaruman]

I pulled the TCM from a 1990 L wagon with the letters EE stamped on the side of the unit. Its identical to the original one.

[AWD_addict]

Good info, thanks.