AW4 diagnosis for dummies

I swapped a '95 4.0L/AW4/231 into my 91 XJ ECORS racerig. I used all the sensors/computers from the donor, with the exception of the CPS and the coolant temp sensor on the rear of the head The electrical harness is from the 91. For tranny cooling, I am bypassing the radiator, and have a ~12"x8" aux cooler right in front of the engine's aux. fan. This fan is disco'd from the ECU and wired to a toggle, always switched on during races.

This ran fine at the beginning of the race a few weeks ago, but after about 30 mins of hard racing in 4HI, the engine temp started spiking. Shortly after that, the AW4 stopped pulling. The tranny dipstick was bone dry (I know the fluid level started off perfect). It was hard to tell where it leaked out, but I think it was coming out between the engine/tranny. When we were filling it up, we probably overfilled it, but it started coming out the vent tube, hard to say if it was also coming out between the engine/tranny. It was strong enough to go a mile or so, but that was it, race over.

Now I'm trying to figure out what went wrong, how.what to check, etc. The tranny will engage fine in reverse, but will not go forward without high revving, and it still slips.
I've searched and found lots of information here, but to be honest, I'm confused where to start, any help is greatly appreciated.

To much going on to diagnose over the internut IMO.
A few quick thoughts, I always separate the tranny cooler from the radiator a bit, makes cleaning easier and avoids rub throughs. If I was racing I'd put a loop of fin tubing under the radiator to pre cool the tranny fluid before my primary cooler.
How did you adjust the cable, throttle control (TV cable, transmission valve cable, same thing different name)? The TV cable controls pump pressure somewhat.
Vent your hood some way.
Use racing or non foaming tranny oil. If you put an expansion can on top of the tranny vent, if the fluid does foam and spit some, it will expand in the can and reform into drops that may eventually drain back down into the tranny.

I put a temperature sender in my tranny pan, the same one used for the motor. Not ideal but when the tranny starts to heat up, you notice quick enough. I use the same temp gauge in the gauge cluster, just switch between motor and tranny.

Not really an answer I know, just a couple of ideas.

Fluid level and condition? Pump working? Check the fluid level engine off, then start the engine and check again. If the pump's ok the level will drop. But you said it has reverse so the pump's probably ok. Frankly it sounds like the trans is toast and the fluid should reflect that.

try adding another pint or two of fluid and check your solenoid resistance. Check the ground on the inner driver side fender right behind the ECU. Try driving it with the TCU unplugged (you will get 1st in 1-2, 3rd in 3, OD in D.) My bet is that one of these is your problem. If the ground goes bad, your TCU generally will go haywire and will force you into second gear (both solenoids on) no matter what anything else says. If something else has an issue (NSS, TCU in general, etc) you will be trying to start out in OD with the torque converter unlocked (both solenoids off) and it will feel like your clutches are toast. Unplugging the TCU and driving it like a standard will eliminate the possibility that something stupid is going on electrically.

I've had all three of these (low fluid, starting in second due to bad ground, starting in OD due to other flaky issues) too many times now to count. Always easily fixed. One of these days I'll get around to welding a better ground stud to the inner fender so the selftapper stops digging into my tire, which both rips the tread up and pushes the selftapper out, screwing up the ground again.

8Mud said:

...How did you adjust the cable, throttle control (TV cable, transmission valve cable, same thing different name)? The TV cable controls pump pressure somewhat...

Click to expand...

I didnt adjust anything. Is this the cable that goes from shifter to tranny? The red line on the shifter doesnt quite line up the letters, maybe this is part of my problem.

JJacobs said:

Fluid level and condition? Pump working? Check the fluid level engine off, then start the engine and check again. If the pump's ok the level will drop. But you said it has reverse so the pump's probably ok. Frankly it sounds like the trans is toast and the fluid should reflect that.

Click to expand...

the fluid looks great...all the old fluid dissappeared and we overfilled it with new. I fear your diagnosis is correct, just want to make sure I'm not overlooking something dumb, like aground stud...

kastein said:

try adding another pint or two of fluid and check your solenoid resistance. Check the ground on the inner driver side fender right behind the ECU. Try driving it with the TCU unplugged (you will get 1st in 1-2, 3rd in 3, OD in D.) My bet is that one of these is your problem. If the ground goes bad, your TCU generally will go haywire and will force you into second gear (both solenoids on) no matter what anything else says. If something else has an issue (NSS, TCU in general, etc) you will be trying to start out in OD with the torque converter unlocked (both solenoids off) and it will feel like your clutches are toast. Unplugging the TCU and driving it like a standard will eliminate the possibility that something stupid is going on electrically.

I've had all three of these (low fluid, starting in second due to bad ground, starting in OD due to other flaky issues) too many times now to count. Always easily fixed. One of these days I'll get around to welding a better ground stud to the inner fender so the selftapper stops digging into my tire, which both rips the tread up and pushes the selftapper out, screwing up the ground again.

Click to expand...

I've seen that self tapper before, it always gets bent over by the tire. It would be sweet if I found that ground loose and it fixed all my troubles.

drop the pan, solenoids are right there? (I can probably search the answer here)

Yep, solenoids are right there once you drop the pan. I hate scraping RTV off things and hate ATF dripping in my face, so I'd try the other stuff first. You can test the solenoids resistance-wise without dropping the pan.

The TV cable (throttle valve cable, not tranny valve cable) is the one that goes to the throttle body from the transmission. Adjust it: http://www.naxja.org/forum/showthread.php?t=1015963

That ground stud is a prime suspect if your HVAC blower and/or 4wd indicator lights act funny occasionally. It came loose again a few nights ago at a stop light and my engine stalled out (think the one under it also got loose), grabbed the 8mm nutdriver, popped the hood, fixed it and started it back up before it went green. The guy behind me was like :shocked: :roflmao:

search found this dude from 1985...
http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html
I have a lot better direction now, thanks guys

Looks like mechanical damage. I still havent dropped the pan, but did all the electrical checks I could, without backprobing the TCU connector wires. Solenoids have 12-13 ohms, got power to the TCU, brake pedal changes the voltage on the circuit its supposed too.
The tranny is way overful with fluid, but with I drove it up/down the street. It takes a lot of RPM before it catches in 1-2 and moves. Reverse is fine. After 5-10 mins of testing, the fluid smelled terrible. Its not leaking anywhere, I think it must have boiled out at the race.

Re-reading this thread, I realized I still need to check/readjust the TV cable.

RenegadeT said:

Looks like mechanical damage. I still havent dropped the pan, but did all the electrical checks I could, without backprobing the TCU connector wires. Solenoids have 12-13 ohms, got power to the TCU, brake pedal changes the voltage on the circuit its supposed too.
The tranny is way overful with fluid, but with I drove it up/down the street. It takes a lot of RPM before it catches in 1-2 and moves. Reverse is fine. After 5-10 mins of testing, the fluid smelled terrible. Its not leaking anywhere, I think it must have boiled out at the race.

Re-reading this thread, I realized I still need to check/readjust the TV cable.

Click to expand...

The TV cable is the one from the tranny to the throttle body. Only reason I mentioned it, was a lot of people forget about it. Two function valve, one function is near full throttle, passing gear/downshift. The other function is the adjust pump pressure, to throttle position.