I have a 94 p/u, 3.0, auto trans, no a.d.d., manual hubs. When trans oil is cold, 4wd works, as soon as it warms up, no 4wd, low or high range. Transfer case range selector works, just won't transfer power to front driveshaft. With all four wheels in air, oil cold, I can't hold front driveshaft stopped, as soon as oil warms, i can grab it with my hands and stop it from spinning. Any ideas?

 

Maybe a little more info.

Driving to catch a plane, AT light comes on...A small prayer and 50 miles later I make it to the airport with trans fluid all over the bottom of my truck and back window of my shell.

When I got back I took it to a shop and they said the trans was toast. Unfortunatley I lived 180 miles away so I luckily babied it back with no problems

I removed the tranny, hauled it back to the shop and had it rebuilt. Everything seemed OK until it overheated again...so I flushed out the dex with valvoline synthetic. I've had no problems since with the over heating but just recently realized that the 4wd wasn't working..I don't know if it ever worked since I got it back, the 4wd light works and the low range works, just no 4wd..

note (1)
The wierd part is... When I first start messing with it, when it's cold, all 4 tires raised, it seems to be working. The front drive shaft is spinning and no way can I stop it, throw it into 2h, I can stop it, throw it back into 4h or 4l, no way, can't stop it, drop it off jacks, drive 5 minutes to check it on a dirt mound, no 4wd, drive it back and jack it up again and I can reach in and stop the front drive shaft, 4h, 4l...NO 4wd.. Wait 3-4 hours.....see note (1)

It's driving me to drinking...more.

 

Is that the chain-driven case? If it was driven without fluid, the chain probably got stretched, and is slipping when it's heating up.

 

is there any noise coming out of anywhere? like skipping or grinding?

 

what about any churning and bubbling? It could be a solenoid not working in the tcase. When it heats up it could be shorting out and not opening or closing all the way. Just an idea disconnect your solenoids and see what happens. On my 3.4 swap I dont have first gear yet. Disconnect the solenoids, I get first gear. By disconnecting them it will rule out if it is electrical or mechanical. Just an idea.

 

i don't think it's a solenoid because it shifts to low and high range, just doesn't turn front driveshaft, which i think is controlled in valve body but I don't know how to test or troubleshoot.