AW-4 not shifting when warmed up

Hi everyone!
I'm new to this forum and I just purchased a 1990 XJ 4.0 4x4 Auto.
It was used as a beater and I'd like to get it running so I can take it off road and camping. It will shift and drive when cold but after running for 10 mins or so, the transmission will not shift into any gear. I don't hear any sounds from under the vehicle when I shift the lever into a gear, any gear but the engine will rev when the pedal is pressed but no movement. It will roll when in neutral. I don't know anything about XJs yet, so I'm pretty much a newb, but am excited to learn all that I can so that I don't have to pay an arm and a leg at the shops. Any wisdom is much appreciated! Thanks!
Dan

What is the fluid level and condition?

Cruiser- the fluid is full and a nice cherry red... Should I change the tranny oil? Thanks for getting back to me

I'd check the solenoids for proper resistance while it's hot. Could be they check out when they heat up.
I think it's 7-11 ohms, you'll need to search.

Look underneath the Jeep real closely. Follow the trans cooling lines from the trans to the radiator. Make sure neither of them is crushed.

87manche said:

I'd check the solenoids for proper resistance while it's hot. Could be they check out when they heat up.
I think it's 7-11 ohms, you'll need to search.

Click to expand...

I think it is 11-14 ohms.

There is a fuse under the glove box, behind the passenger side lower dash that feeds the AW-4 computer, TCM. Pull the fuse and see if 1-2 shift position works, and try shifting manually. That bypasses the TCU and solenoids!!!! Of course, make sure the fuse is not blown too!!!!

If you change the fluid, drop the pan and test the solenoids with an ohm meter, and only use Dex-III fluid!!!!

Some one might have put the wrong fluid in it.

Thanks guys! I'll start with dropping the pan and completely flushing the oil and replacing the filter and add new oil to see if that's it. I'll test the solenoids while I'm down there and then I'll try pulling the fuse. I'll keep you guys posted on my progress. It probably won't happen till after Thanksgiving weekend. Happy Thanksgiving to all of you!!!

So here's an update:
I drained the tranny and took the tranny filter out, looked at it and realized that it was all clogged up so I bought a new one and flushed out the tranny. I put in new fluid and filter, cleaned out the pan and around the reachable parts by the solenoids, and viola! Fixed tranny! Thanks for all your help!

It's a wonder what proper maintenance will do.

Keep an eye on the fluid color for a while. Might want to do a coupla drain and fills as time goes on.

What do you mean by "flushed" the tranny?

Cruiser54- will do. I have a back up filter just in case...
Bimmerjeeper- I meant that I drained the oil, filled with new oil, then drained again. Hope this helps.