AW4 Slipping in Drive...Yes I've searched

I have a 1990 XJ which slips in Drive only. In 1-2 & 3 it is fine. I can manually shift from 1-2 to Drive and it does fine. I have abouT 165000 miles on the tranny. I have searched and find conflicting info...or I may be misreading the info...change to Dextron III...don't change use ATF4...I've always used ATF4.....I understand that different fixes work for different people. I've dropped the pan, replaced the filter and fluid, adjusted the
tps. It shifts good. Is this a death sentence for the tranny? Will I need to replace the Tranny. Any help would be greatly appreciated....Thanks in advance

Unplug the TCU and drive it shifting manually.

If the problem persists the trouble is hydraulic/mechanical; if not then look for electrical: TCU, solenoid(s), wiring.

The AW4 was designed for Dexron, so I usually recommend that. Some folks have reported no problems running ATF4, but others have had issues with slipping.

Is your tranny truly slipping, or is it just not locking up the torque converter? As a test, while cruising at highway speeds reach over and tap the brake pedal with your left foot. The t/c should unlock and the rpm should jump up a few hundred rpm briefly. If it doesn't I would check the brake pedal switch for the trans computer. On a 1990 its a white switch high up on the brake pedal and will have a vacumn line attached if you have cruise control. It should measure zero resistance with the brake pedal not applied. If can be adjusted and even taken apart to clean out any gummed up grease.

Thanks for the info....Being I only have weekends to work on the XJ, long work hours..anyway....is the TCU the computer looking box next to, above the gas pedal? It is about 6"x6"x2". I failed to mention my cherokee is a 1987 with 1990 running gear, replaced about 165000 miles ago. Has worked flawslessly since. Will the suggestions still work? I looked and there is no white switch on the brake pedal only the brake light switch.

Should be on PS by the glove box.

That box on the drivers side would be the engine computer. The trans computer is on the passenger side, bolted to the backside of the trim panel below the glove box.





Have a look at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html for guidance on testing various things at the trans computer connector. You should be able to check the brake pedal switch works at the trans connector.

The switch on the brake pedal is way up near the top of the brake pedal and looks like this. It can be popped apart and cleaned up.

lawsoncl,

You have this down to science now, LOL. Nice post and images!