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4EAT TCU Questions (96 Legacy Outback)


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Did you install the JDM TCU, or did you just use what was in your car? The 4.44 probably needs a 4.44 TCU in it. JDM not necessary. The shift maps are the only thing that changes from the USDM and JDM. Usually sportier shifts in the JDM, but not needed to make it run. The reason you need a 4.44 TCU is because if the ratios are off enough from the original TCU ratio, then the TCU can't calculate what it needs to because the 2 vss' are off, and it goes into "limp mode", which might be what is happening to you.

 

What was the ratio of the original trans?

 

The simplest thing to do would be to swap out the TCU and see what happens. It's a crap shoot if that will work for you, but it's the "fastest" and easiest option if you have a spare TCU available.

 

After that you need to start going through the sensors and seeing what's up. The TPS plays a big role in determining shifts, same with both of the vss' and RPM as well. If any of those signals are messed up, then the trans MIGHT not shift right.

 

You getting any codes?

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The reason you need a 4.44 TCU is because if the ratios are off enough from the original TCU ratio, then the TCU can't calculate what it needs to because the 2 vss' are off, and it goes into "limp mode", which might be what is happening to you.

 

i've dropped a 4.44 out of an EJ25 and installed a 4.11 (also AWD to FWD! :eek:) without swapping the TCU and saw no difference after about 60,000 miles of driving.

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i've dropped a 4.44 out of an EJ25 and installed a 4.11 (also AWD to FWD! :eek:) without swapping the TCU and saw no difference after about 60,000 miles of driving.

 

You feel into the "might" category :)

 

You should be fine with that little of a change. But I know for a fact, because this happened to me while modding my TCU, that going from 3.7 to 4.11 throws a duty c code and the awd quits working. The code had to be changed in order to get the legacy TCU to work with my loyale's 4eat because of the 3.7 ratio. The TCU is forgiving enough for close ratios, like 4.11 to 4.44, but not so much for bigger jumps.

 

That's why I suggested it might help, but without knowing what the final drive ratio for the original trans, it's hard to say for sure that the tcu is/is not the problem.

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Only reason I suggested swapping out the TCU is because 15+ year old hardware can be unreliable at times, and they are usually easy to get to and easy to swap. Probably won't do a thing, but it doesn't hurt to be sure that it's not the TCU causing problems.

 

Clay, this might be a dumb question but it hasn't been mentioned, did you swap the rear diff to match the trans? The rear diff has to match the trans or all sorts of bad happens...

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Only reason I suggested swapping out the TCU is
i was asking because i'm curious if whatever causes the issue could cause downgraded performance in other swaps, like mine, even though it works? less gas mileage, different...? but with an EJ18 i guess it doesn't really matter :lol:

 

did you swap the rear diff to match the trans? The rear diff has to match the trans or all sorts of bad happens...
AH, right!
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i was asking because i'm curious if whatever causes the issue could cause downgraded performance in other swaps, like mine, even though it works? less gas mileage, different...? but with an EJ18 i guess it doesn't really matter :lol:

 

If it works, it will works just fine. The TCU code is forgiving enough, that it will just continue to operate normally until it doesn't work, then it will go into a limp mode. There is no in between or anything like that. It's pretty black and white with these things :) Gotta love older, stupid electronics!

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Yes I did swap rearends. Installed a 04 foresterXT 4.444LSD.

 

Yes stock tranny was 4.11.

 

Crazy thing is. Installed tranny low fluid so filled it up. Test drove it had the problem. So I drained fuild completely. Two days later filled it up test drove it, it work fine for a lil bit then went back into limp mode. So I installed the cooler drained sum fluid, filled it back up same problem, limo mode.

 

Oh also I unpluged the battery everytime to reset comp.

 

Note my speedo isn't worked since install.

Edited by bratclay
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bratclay - no flashing ATF light?

make sure the trans plug is fully seated and none of the pins are bent.

trans pan isn't dented or damaged?

 

disconnect the trans connector entirely and tell us how it drives. it should default to 3rd gear (but the clutch pack will be locked). it'll at least also render your vehicle drivable while you work the kinks out.

 

to compensate for the default to full-lock on the transfer clutches you can either just directly power the Duty C yourself so as to allow FWD, requires just splicing into one wire, or remove the rear half of the driveshaft. i've done this before to keep a borked trans drivable. it's always in 3rd gear so it's a little gutless at start up but otherwise is perfectly drivable, even on the freeway.

 

If it works, it will works just fine. The TCU code is forgiving enough, that it will just continue to operate normally until it doesn't work, then it will go into a limp mode. There is no in between or anything like that.
awesome, great, exactly what i wanted to know for my swapped leg.
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Yes I have ATF light flash.
that's the solution to all the riddles - you need to find out that code. you need to do the secret handshake to get it to flash the code for you. that's probably going to help a good bit to know that rather than just guessing.
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that's the solution to all the riddles - you need to find out that code. you need to do the secret handshake to get it to flash the code for you. that's probably going to help a good bit to know that rather than just guessing.

 

Ok I checked codes. It flashed one long then a quick one. So I'm guessing code 11?

 

New up date I got speedo fixed it and gotten pulled outta dash. Still bind so I found where the plug is for FWD took the fuse holder with fuse in it and pluged that in. FWD lite on and very minimum binding. And the trans is shifting through all the gears. I will be bringing it to the show so maybe someone can help.

 

Thanks Clay. And for all your help and advice

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Well I've followed a bunch of different threads about this Torque binding problem as I am experiencing it in my 97 outback legacy 4EAT.

 

Here's what I have done so far.

 

Got the code 24 and went ahead and did a duty-c change. The only thing I think could have been done wrong was putting the spring it its correct location as it sprung out when I took the casing off. If anybody thinks that could be an issue let me know. I'm not sure it is in the correct location.

 

The fwd fuse has never done anything. I've done several atf changes.

 

The lastest that I've done is going thru the diagnostice manual for the code 24 as follows it failed 1.4) and 3. It did pass the other ones.

 

1. CHECK HARNESS AND CONNECTORS BETWEEN

TCM AND DUTY SOLENOID C.

1) Turn ignition switch to OFF.

2) Disconnect connectors from TCM and transmission.

3) Measure resistance of harness connector between

TCM and transmission.

Connector & terminal / Specified resistance:

(B52) No. 3 — (B9) No. 11 / 1 Ω, or less

 

4) Measure resistance of harness connector between

TCM and body to make sure that circuit does not short.

Connector & terminal / Specified resistance:

(B52) No. 3 — Body / 1 MΩ, or more

 

2. CHECK DUTY SOLENOID C’s GROUND LINE.

Measure resistance between transmission connector

receptacle and transmission case.

Connector & terminal / Specified resistance:

(T4) No. 4 — Transmission / 1 Ω, or less

 

3. CHECK DUTY SOLENOID C.

Measure resistance between transmission connector

receptacle’s terminals.

Connector & terminal / Specified resistance:

(T4) No. 11 — No. 4 / 9 — 17 Ω

 

I am now at a loss, as I think that there is a short circuit issue and I don't know how to go about fixing it. Let me know what you guys think. I also did just go out and pulled the code again got 24, but what I did notice is that when I restarted the car after pulling the code, the fwd light was one for about 1 sec, but only after pulling the code (this is of course with a fuse in) not sure if this means anything.

Edited by theburro
new update
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