AW4 slipping in drive and 3rd, not in R or 1-2

I have a 92 XJ w/ the AW4 and about 200,000 miles. I just got this XJ a couple nights ago. Last night it would barely go forward (I rev it and it would not do anything) when going from a stop in either "D" or 3rd. In 1-2 or reverse it worked fine. On flat ground or with some momentum "D" works fine, it's just when it starts from a stop on a hill. Fluid level and color is fine. And this is on my steep driveway after starting the vehicle, so it is not overheating. Any ideas?

I dont know but it could be the band for 3rd and 4th. But I dont even know if they have adjustable bands in them for those gears?

A bad TCM could do that. If the TCM is not working the AW4 will be in 3 when the selector is placed in 'D'. Drive it around the block while shifting it manually starting in 1 and shifting as the speed increases. If the TCM is bad, overdrive will not work. The other gears will work by shifting manually. I drove my XJ for days on city street with the TCM on the back seat.

I'll give that a try, I'm going to drop the pan and see if there are any surprises as well. Can you adjust the bands on a 92 AW4?

When my AW4 acted up, the TCM was good. However, the two shift solonoids were bad. They were shorted to ground when tested with an OHM meter. I replaced the three solonoids for peace of mind. I have had no problems since then. That was about 80,000 miles ago.

If the TCM is bad (or the fuse is simply blown), you'll get 4th in (D), 3rd in (3), and 1st in (1-2). This is a failsafe as you don't want the tranny dropping into 1st gear on the freeway if the fuse pops. The first test in the FSM is to pull the fuse and verify this is what happens. From the description, the problem sounds like its on the electrical side of the house. Trying to start in 4th it will seem like it's really slipping.

In order of probability for AW4 problems:
- Erratic shifting is usually the TPS, but doesn't sound like your problem
- TCU doesn't have power, such as blown fuse. Check for power at connector.
- Bad solenoids. Easy to test using a meter at the TCU connector.
- Bad speed sensor. Cause it to not upshift - not your problem.
- Bad TCU. Fairly rare. I'm only heard of 4 confirmed bad ones.

lawsoncl,

Thanks for the reply, I'll try the fuse first, then I'll try the solenoids when I pull the pan. Hopefully there is not allot of shavings in the pan. If one or more of the selenoids are bad, where is a good source for replacements?

Also to add to the above info, the only thing that changed on the cherokee right before this happened, is I removed the stock alarm system module from the harness. I know the module talks to the ecu, so I had to trick it so I would not get a "no start" problem, but I am pretty sure the module doesn't talk to the TCM. Correct me if I am wrong. Thanks.

The TCU does get a throttle position signal from the ECM (as opposed to the Renix setup which had a dual output on the TPS sensor). They also share an OBDI connection, but that's just so you can pull codes from the TCU. I don't believe they actaully talked in the OBDI setup - not like the OBDII setup where TCU faults will throw a check engine light and codes.

A meter used at the TCU connector can really help check things out, such as checking the solenoid resistances thru the whole harness, checking that you have power to the TCU (yellow and red wires I think), and checking that you have a changing voltage from the TPS.

techno1154 said:

A bad TCM could do that. If the TCM is not working the AW4 will be in 3 when the selector is placed in 'D'. Drive it around the block while shifting it manually starting in 1 and shifting as the speed increases. If the TCM is bad, overdrive will not work. The other gears will work by shifting manually. I drove my XJ for days on city street with the TCM on the back seat.

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x2.

When I had my TCM disconnected I wondered why I wasn't going anywhere when in D. Then I remembered I disconnected the TCM when I removed the lower dash panel.