stuck in first aw4

[PETEY]

What do I need to look for? I was driving home when transmission started downshifting at the wrong moments. I gave it just a little gas and it popped backed into 4th. When I got to a stop sign and started again, will not shift. It appears to be stuck in 1st gear. This is a first for me. It's 90 with a aw4

[sidriptide]

i'm thinking throttle-position-sensor maybe.. it's signal is used to control shift points.

[CaptTrev]

i had a weird tranny problem a few years ago...
it would start off in 1st gear fine.......rev a little too high, and then skip 2nd gear and go right into 3rd (and lug the engine till i got up to speed)

after trying a lot of different things
changed tps - no fix
changed out all 3 (or 4, i forget) shift solenoids in the tranny - no fix
bought new TCU (tranny control unit=tranny computer) = fixed

let me know if u need further info on a TCU
i bought mine new from the deal for like $200 i think
but im sure you could find a junkyard one for cheaper
its really easy to replace too

CaptTrev

[langer1]

What do I need to look for? I was driving home when transmission started downshifting at the wrong moments. I gave it just a little gas and it popped backed into 4th. When I got to a stop sign and started again, will not shift. It appears to be stuck in 1st gear. This is a first for me. It's 90 with a aw4
Check the TRANS fuse. Unplug the TCU and try to shift Manually. If it shifts manually the transmission is fine and the problem is in the TCU or tps or power fuse.

[PETEY]

thanks guys. gonna go look

[seymouj]

One more thing to check - VSS (Vehicle Speed Sensor) on your t-case. If it is not working, your tranny will not shift out of first.

[langer1]

One more thing to check - VSS (Vehicle Speed Sensor) on your t-case. If it is not working, your tranny will not shift out of first.
I don't think a 90 had one, I know 87,88,89 don't.

[PETEY]

A 90 does not have a vss, just a cable and a speedo gear. I went out and removed the tps, worked the lever back and forth and cleaned the conectors. Now it shifts, but WAY too late in the rpm range. it won't downshift when i punch the gas. At least it moves out of first now. This makes me think i need a new tps. I went and ordered one should be here tomarrow. I let ya know if that fixes the problem.

[8Mud]

A 90 does not have a vss, just a cable and a speedo gear. I went out and removed the tps, worked the lever back and forth and cleaned the conectors. Now it shifts, but WAY too late in the rpm range. it won't downshift when i punch the gas. At least it moves out of first now. This makes me think i need a new tps. I went and ordered one should be here tomarrow. I let ya know if that fixes the problem.
If it won't downshift when you punch the gas, you probably need to adjust the TV cable. I´m pretty sure the TV (kickdown) is fairly independant of the TPS inputs to the TCU.
TPS adjustment, seems to have some affect on shift points.

[Lonestar]

Make sure you adjust the new TPS correctly when you install it or the shifts will be messed up. Also, the TV cable controls line pressure in the tranny but doesn't control the shift, and the AW4 does have a vss located on the driver side of the tranny near the 4x4 adapter.

I had problems with mine a while back and learned a lot about the AW4 in the process. A used TCU from the junkyard fixed my problem.

Bryan

[PETEY]

ya I noticed that the bolt holes are positioned on the tps that will allow it the whole thing to rotate. I suppose I will install it, drive a bit then adjust. I hope a new tps will fix the problem because a new tcu sound expensive and there isn't any xj's in the wrecking yards around here.

Oh ya, where exactly is the tcu under the dash? is it the big grey box under the driver's side?

[8Mud]

The TCU is on the right under the glove box. Do a search on TPS adjustment. It doesn't have to be perfect, but it has to be close. If it's really off, it can be dangerous (It can idle really high). The TPS is a two part, actually a dual function sandwhich which inputs both the motor ECU and the tranny TCU.
I'd try adjusting it before buying a new one.

[PETEY]

hmmm.. just did a search for tps adjustment and read that they hate water. It was raining all day and it sits right underneath my lebarron hood vents

[PETEY]

New tps, problem solved. Thanks guys for your input. I learned a few more things about my aw4.

[8Mud]

Does it full throttle downshift now? I´m pretty sure the full throttle downshift is mostly independent of the TPS. And is mostly a hydraulic (TV valve) bypass inside the tranny. The TV valve is multi function, passing gear and pump pressure control. My TPS was screwed up when I bought my XJ and failed one other time, but it always full throttle downshifted (as long as the TV cable was properly adjusted) no matter what my shift points or lack of shift points were.

[PETEY]

Yes it downshifts just fine now. Everything works just fine. Again I thank everybody that responed. I learned some more about the aw4. Actually I was worried becuse this tranny was rebuilt last year. It was an easy fix.

[seymouj]

Glad you got it fixed but just for the record, I replaced the VSS on my 87 with one from a donor 89. I don't think the VSS has anything to do with the speedometer but it does provide input to the tcu. It is located behind a bracket that mounts the t-case linkage. FSM stated that the tranny would not shift out of first if the VSS was faulty. I had already swapped tps, tcu and solenoids with no change. VSS was my problem (must be a rare issue). By the way, t-case was 242 in both cases but IIRC I got the info from my aw4 FSM which makes me think it should apply to either t-case (I will check tonight). I can take pictures when I get home if needed.