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1992 XJ AW4 doesn't want to shift

R

Runner-Man

NAXJA Forum User
Location
Georgia
Hello all, and thanks for the help in advance.

I've recently picked up a '92 XJ. 4.0, 4x4. It had been sitting for three years, and is quite the project - already spent more on it than I paid for it.

When I first got it, it didn't want to shift, at all. Replaced trans filter, did a fluid change. Eventually replaced the TPS, and it started shifting.

Then it started not shifting when first started up (morning or afternoon). If I just drive it, let it rev up to 3,000 rpm or so, then let off the gas and get back on it again, it will shift. Usually after this it will shift fine; sometimes it takes a couple of tries, but no more than two. From then on it's fine until it cools down again. I did a bunch of research, found out the TPS could be the culprit. Tested it, and it seems OK. Replaced it anyway. It still does it.

Any ideas on what to check next? Just as an aside, with a 3" lift and 31's it's getting 13.4 to 14mpg with mixed (mostly highway) driving. I don't know if that's related, but it's just more information. I'll take suggestions on how to improve that, too!

Thanks!
 
The AW-4 transmission has the specified Dexron-III/Mercon fluid installed, and not DEX V or any other type ? Many XJ Cherokee owners report shifting issues that clear up when other fluids are drained, and Dexron-III/Mercon is installed. I might also suspect a faulty or mis-adjusted PRNDL / NSS ( Neutral Safety Switch )

A basic search of the Internet will locate the AW-4 Service and Diagnostics info. These transmissions are known by multiple names and codes, including: AW-4, AW4, A340, A340F, 30-43LE, 40-30LE, AW30-43LE, AW40-30LE, Aisin AW, Aisin Seiki, Aisin-Warner

I will some AW-4 info to your Private Message mailbox
 
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Mine has been doing this for over two years, 75+ thousand miles. I've changed practically everything, (besides the tranny, map sensor, and t case,) in the jeep in this time and it has not made any difference. My transmission guy, who hates aw4s and won't work on them, says its just wear in the valve body. It is very temperature sensitive and hardly does it in the summer, but really bad in the winter. It will also cause a delay in shifting into reverse.
 
Thanks for the info, Tim_MN and Unclewolverine. To be honest, I can't remember which trans fluid I installed, since I did it last year, but I've got some left over at home so I'll double check and put the right stuff in it if I didn't the first time. I'm pretty sure I used what the Haynes manual recommended.

It's getting warmer here (Southeast), expected to be upper 70s today, so we'll see if it does it when it's warm out. I have no delay going into reverse, even when cold.

I don't remember the problem last fall, but I didn't drive it much then because of all the OTHER things I was replacing. Pretty soon the only thing original will be the paint.

Thanks again!
 
Unclewolverine said:
Mine has been doing this for over two years, 75+ thousand miles. I've changed practically everything, (besides the tranny, map sensor, and t case,) in the jeep in this time and it has not made any difference. My transmission guy, who hates aw4s and won't work on them, says its just wear in the valve body. It is very temperature sensitive and hardly does it in the summer, but really bad in the winter. It will also cause a delay in shifting into reverse.
Click to expand...

A delay going into reverse is not solenoids. I would suspect the wrong fluid or the throttlebody cable is misadjusted if the shifts are sluggish or delayed when its cold.
 
No one said anything about solenoids? I don't know anything about runner man's, but mine has not had anything except dex 3 in it since I put it in, and I've changed the fluid and filter at least 3 times since then. The TV cable has been adjusted several times too trying to get 3rd gear to shift right, it has never made a difference on the cold shift issue. But my 3rd gear shifting issue, (shifts into 4th almost immediately, ) I've just chalked up to using an 01 tranny in a 95, although it should function the same. Anyhow, im going to believe my tranny guy and trust that the valve body is just worn and I'm going to run it until it quits. Which should be soon, I was only able to run 25k miles before the filter accumulated enough clutch material from the tc to be clogged last time.
 
I just mentioned solenoids because they are a common cause for temp related shifting issues, usually when hot though. Putting an 01 trans into a 95, I assume you dealt with the output speed gear difference?
 
Yes, switched the reluctor wheel and rear housing. I've put on probably 100k since I put it in, it supposedly had 100k on it. I get 14.5 mpg route mileage still, which is what carriers with newer jks get. When it starts slipping I have another 01 tranny to put in with only 100k on it.

Back to the op's issue, when mine first started shifting weird in the morning I asked here and other places, a couple other people had the same issue and no one ever figured it out.
 
Unclewolverine said:
Mine has been doing this for over two years, 75+ thousand miles. I've changed practically everything, (besides the tranny, map sensor, and t case,) in the jeep in this time and it has not made any difference. My transmission guy, who hates aw4s and won't work on them, says its just wear in the valve body. It is very temperature sensitive and hardly does it in the summer, but really bad in the winter. It will also cause a delay in shifting into reverse.
Click to expand...

It sounds like you need a real trany guy! The AW4 is a solid transmission and I dont see wearing a valve body out with nothing but fluid running thru it unless you never change your fluid.
 
RCP Phx said:
It sounds like you need a real trany guy! The AW4 is a solid transmission and I dont see wearing a valve body out with nothing but fluid running thru it unless you never change your fluid.
Click to expand...

I agree the AW4 is pretty robust, and 95% of the time it's a TPS, solenoid, wiring, or throttle body cable issue. Very rarely is it the computer, as I've only heard of a few confirmed bad TCUs. For your symptoms, I'd be real curious to stick a meter on the #2 solenoid wire to see when the TCU is commanding the shift versus when it actually shifts. The 1-2 shift goes from just the #1 solenoid, to both #1 and #2 powered. That would clearly identify whether it's the trans being sluggish to shift or on the electronics side.
 
I would say so if it can tolerate a twin turbo 2jz motor!
 
Update (maybe).

I decided to start testing sensors. When I tried to apply vacuum to the manifold air pressure sensor from the manifold side it wouldn't hold vacuum. I found that my vacuum line from the manifold to the sensor was leaking. I replaced it and the MAPS holds vacuum fine and has good voltage response with change in vacuum. So I took it for a drive and it shifted perfectly. I don't know if that was the problem, or if it's just that it's about 80 degrees out now and it's "Pre-warmed up". This problem may be "cured" until November.

Also, I used Valvoline DexIII when I changed the filter and fluid after I bought it.

The resistance on the manifold air temperature sensor seems a bit low with engine at operating temperature -1350 ohms- the manual says it should be about 4000 ohms, but it's 9,200 when cold. It's supposed to decrease as incoming air temp increases, so it is doing that. I may replace it just for the heck of it. The coolant temperature sensor seems to be responding as it should.

I'll see how she goes next week as I try to find a new axle assembly to swap out the existing extremely noisy axle. Then it will be time to fix the A/C!
 
Just thinking out loud here:

There may not have been anything wrong with the transmission at all - with the vacuum leak to the MAP sensor, the ECU may have been in "limp mode" and somehow altering/suppressing the TCU's normal shifting algorithm and causing the symptoms you mentioned.

You could try doing the ignition key trick to see what codes are in the ECU (blinks on the Check Engine light, see here for instructions). I'd bet on at least one of the MAP sensor codes being there.
 
I never could get the key on off deal to work on my 98 xj however it worked great on my 97 tj
 
On XJs, it seems like the key trick only works on 91-95 OBD-1 models...
 
Rob Mayercik said:
Just thinking out loud here:

There may not have been anything wrong with the transmission at all - with the vacuum leak to the MAP sensor, the ECU may have been in "limp mode" and somehow altering/suppressing the TCU's normal shifting algorithm and causing the symptoms you mentioned.

You could try doing the ignition key trick to see what codes are in the ECU (blinks on the Check Engine light, see here for instructions). I'd bet on at least one of the MAP sensor codes being there.
Click to expand...

Thanks for the reply, but...

No codes - it was the first thing I checked.

Drove it today (temperature is 41 degrees F), and the problem came back. No shift from 1st to 2nd, so I let it rev to 3,000 rpm, "blipped" the throttle so it dropped down to no lower than 2,000 rpm, got back on the throttle, and it shifted into 2nd. After stopping at the end of my road I had to do it again to get it to shift, but after that it worked fine.

It is definitely temperature related; it doesn't do it when it's warm. 65 degrees plus, no problem. 41 degrees or less, it has the issue. I don't know the transition temperature.

Coolant temp sensor checks out, Intake air temperature sensor checks out, manifold air pressure sensor checks out.

And 13.2 mpg with a 3" lift and 31's. Grrrr...
 
If your still running stock gear ratio 3.55 that may explain your gas mileage?
 
Ineteresting. About the only other thing I can think of is to maybe disconnect, inspect/clean, and reconnect all the electrical connectors on the TCU and transmission, including any grounds. Might be something is dirty/oxidized from age and/or sitting and isn't making a good connection until things warm up slightly and expand?
 
If I had more spare time I'd hook up some lights to tell me what the computer is telling it to do vs what its actually doing but I don't. I don't feel like it's electrical, but I have nothing to back that up. The good news is that it dosent seem to get worse over time and miles. This is my second winter of it doing it and something like 60-70 k miles in that time.
 
jeep ride said:
If your still running stock gear ratio 3.55 that may explain your gas mileage?
Click to expand...

It is currently 3.55. What should I be running?

When I check the speedo it's pretty close to dead on (at least according to Google, if you can trust it). The 31's aren't that much bigger than the tires that were on it when I got it. Just not nearly as cracked and knotted!
 
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