AW4 Not Shifting Out of 1st Gear??

[Quanah_the_89_MJ]

New Comanche owner here. 1989 SB 4WD Auto with only 25k miles on the original engine/chassis, but I'm having issues with getting out of first gear:

 

1. Finally got the truck running after some basic maintenance, but went for a drive and noticed the truck slipping out of gear from 10-20mph. It would disengage, catch, speed up, disengage again, slip, reengage, etc, and afterwards was seemingly stuck in 1st gear... It did this for about 2mi of driving before I parked it for an hour to cool off (out of my worry of overheating because of high RPM's and the coolant reservoir almost melting my hands)
2. I've done some slight research about the throttle position sensor *TPS* and found that this wasn't the issue because I've replaced it. I know that this can cause things to go wonky. I haven't done much adjustment, but I installed the new sensor, truck idles fine, but doesn't shift out of 1st gear. Then adjusted it, truck idles WAY too high; didn't bother driving it. Adjusted it the opposite way and the truck seems to want to quit. Found a happy medium and the truck idles perfectly with no rumbles or shakes at a stop and rolls through 1st gear like a stick of butter. 
3. Trans fluid is perfectly full and clean/red.
4. After some investigating, the TCU under the passenger dash board was oddly not secured to anything and rattled like crazy. I checked the harness connection and its solid. The 10A fuse was good, but pulled it and out and VOILA.. it shifts perfectly ONLY if using the steering column to shift from 1-2, then 3, then D.... 

 

After all of the research I've found from you gentleman and gentleladies, I'm hearing NUMEROUS fixes to the AW4, but every write up is different. Any guidance and instigating to my diagnostic methods is appreciated. A list of replacements is below (incase that affects anything).

 

(Truck was running perfectly fine before the mods listed below; I'm trying to eliminate all variables)

 

- 31"x10.5x15" tires

- 3" hockey puck lift in the front 

- 2.5" shackle lift in the rear and sway bar mount extension

- New throttle position sensor

- Flushed the radiator, new Thermostat

- New fuel injector body on cyl 3

 

Please help. Auto shop wants thousands...

 

 

[cruiser54]

Go to www.cruiser54.com and complete Tips 1,3,4, and 5 first. Tip 10 would be a good one to do also. 

[gogmorgo]

Auto shop wants thousands to do what exactly?

 

If the trans is acting fine when you shift manually that’s a solid indication the problem is related to the shift computer and/or wiring. Following Cruiser’s advice is good for that sort of thing. Would also be good to check his procedure for properly adjusting the TPS, I’m surprised he didn’t suggest tip 8.

Also worth adjusting the kick down cable. Likely won’t do anything but you never know, and it’s quick and easy. https://www.allpar.com/d3/SUVs/jeep/cherokee-transmission.html

[Eagle]

On 3/21/2023 at 11:21 PM, Quanah_the_89_MJ said:

After some investigating, the TCU under the passenger dash board was oddly not secured to anything and rattled like crazy. I checked the harness connection and its solid. The 10A fuse was good, but pulled it and out and VOILA.. it shifts perfectly ONLY if using the steering column to shift from 1-2, then 3, then D.... 

 

 

The basic diagnostic in the factory service manual is to remove the TCU fuse and see if it shifts manually. Your transmission passes that test, so the problem isn't the transmission. That leaves the TCU and/or the wiring.