AW4 Shifting Issue

[PacificEd]

I have just over a week to get my XJ ready for Harlan and I have a problem.

First the details:

1988 Jeep XJ
AW4 transmission
300,000 mile (approximate)
Jeep has sat since September 2023 without being run
It has been stored inside an enclosed shop
Battery was dead with 2 volts
Transmission fluid is full, regular color and doesn't smell burnt

On Sunday, I changed the oil, greased the suspension, and checked the differential fluid. I then installed a fresh Group 34 AGM battery. Jeep started after just a few cranks and ran fine. I backed it out of the shop and let it idle and get up to temp. It backed out of the shop just fine. When I put it in drive (overdrive 4), it took a lot of RPM's to get it moving. It's like it was sluggish. Once rolling, it seemed to run and accelerate fine. I went down the road and back and it was sluggish when I turned around.

On a second trip, I pulled over and had to go up a small incline to pull back out onto the road and it was almost all it could do to pull back on the road. Once I got back to the shop, I dropped it into 3rd gear and it acts the came as 4th. I put it in 1-2 and it jumps to life. Great response to throttle input. I have not tried the 1-2 gear on an incline yet.

At first I thought I may have stuck or failed solenoids. Maybe the transmission kickdown lever is out of adjustment, a fuse, TCM or bad solenoid?

Help! I have just over a week to fix this before Harlan. I know, shame on me for waiting this long.

 

[lawsoncl]

Check that you have power to the TCM. On an 88, there is a fuse in the wiring harness near the TCM. See the second picture here - https://cruiser54.com/?p=58

Disconnecting the TCM and shifting with the shifter is the usual test for mechanical issues. I'm betting no power to the TCM or a bad #1 solenoid, which would cause it to start out in 4th gear. Measure the solenoid resistance at the TCM connector. Should be 11-15 ohms.

It's really not a "kickdown" cable as the trans computer controls when to shift. The cable controls hydraulic pressure and thus shift firmness, based on throttle. If that's out of whack, you'll get either harsh shifting, sluggish shifting, or possibly not shifting at all. With reverse and manually shifting being okay, I doubt that's your issue. Never hurts to make sure it's adjusted though.

 

[PacificEd]

Check that you have power to the TCM. On an 88, there is a fuse in the wiring harness near the TCM. See the second picture here - https://cruiser54.com/?p=58

Disconnecting the TCM and shifting with the shifter is the usual test for mechanical issues. I'm betting no power to the TCM or a bad #1 solenoid, which would cause it to start out in 4th gear. Measure the solenoid resistance at the TCM connector. Should be 11-15 ohms.

It's really not a "kickdown" cable as the trans computer controls when to shift. The cable controls hydraulic pressure and thus shift firmness, based on throttle. If that's out of whack, you'll get either harsh shifting, sluggish shifting, or possibly not shifting at all. With reverse and manually shifting being okay, I doubt that's your issue. Never hurts to make sure it's adjusted though.

I checked the fuse and everything looks good there. I reset the TV cable and there was no change in operation.

I'm going to check the 12V power to the TCM and clean all the connections as per the Cruiser54 link you posted. I think you (along with others) are correct in the #1 solenoid being bad. My plan is to remove the transmission pan and check the solenoids like you suggested. Hopefully, this is where the problem lies and I can get everything repaired and put back together before the trip.

Thanks for your help!

 

[lawsoncl]

Measure the solenoid resistance at the TCM connector before you go to the effort to drop the pan. There is also a connector under the hood as well that's worth checking and cleaning. I've also seen the clamp that holds the wiring on the drivers side of the trans wear through the wiring.

 

[PacificEd]

I was able to check out the transmission last night a little more. The TCM is getting 12V so that was good to see. I then checked the three solenoids. Luckily I have a 1988 Jeep XJ wiring schematic and that allowed us to identify the three solenoid wires to check. It lists them as solenoid 1, 2, and 3.

Solenoid 1: 3 ohms - light blue w/white tracer
Solenoid 2: 15 ohms - violet w/white tracer
Solenoid 3: 21 ohms - white w/black tracer

I feel pretty confident that I have solenoid issues, so I will be dropping the pan and getting them swapped out once they are delivered.

 

[PacificEd]

So if solenoids check out, there is resistance from the TCM plug to each solenoid, and you have 12V to the TCM and the fuse is good, what else could be going on? Bad TCM?

Long story short, we pulled everything apart to replace the solenoids and they checked out at 14.5 ohms and passed the 12V "click" test and it still doesn't shift without selecting the gears manually. It shifts the same with the TCM plugged or unplugged, so mechanically the transmission should be ok. It has to be some sort of electrical signal issue, right?

 

[lawsoncl]

12-volts to both the red and yellow wires at the TCM, pins D1 and D16? Good ground on the black wire on D7? With the key-on and not moving, it should be powering solenoid#1 which is pin D16, blue-tan or blue-white wire. Was that really 3-ohms on Solenoid 1 or a typo and you meant 13?