So, I've got this problem with my 01. When I got it, it didn't have overdrive but, the tranny shifted through all the other gears great and the tranny fluid was full and wasn't burnt. I've spent the last couple weeks researching it and trying things. I've cleaned the NSS, and tried a different TCM. Like I said, the tranny shifts fine and doesn't slip abnormally but, I have zero overdrive and no torque converter lock-up. Any ideas??

 

I'm no wizard here. One of the three solonoids in the AW4 controls lockup. There may be a way to check at the plug to the tranny rear of the dipstick. I think the resistance of the solenoids can be checked.

Also I there is a white switch down on the brake pedal with the maybe black brake light switch. It unlocks the TC when you hit the brake. I'll guess it's normally closed and goes open when the brake is applied, but like said, that's a guess, it may be opposite. Also I'm not sure which years have that, my 90 does.

Checking the codes might help.