1990 XJ Transmission shifting randomly

Have a 90 XJ with auto trans. Trans shifts in between 3-OD gear from 35-55 back and forth during various speeds. Any suggestions on where to start? I bought this jeep 4th hand and it has 206,000 miles on it to date. Should I start at the tranny and do a flush / filter replace or is it a common problem among these? Any suggestions?

The much maligned TPS could be a suspect. A fluid and filter is always a good idea. Its quick and easy on a AW-4. Just beware, if you can get the two piece dipstick/filler tube apart then you obviously know a trick that I don't. On mine, I unbolted it from the firewall, dropped the pan and tube together as one. After that, though, it could be a shift solenoid. If you can do a fluid and filter change yourself then shift solenoids are too difficult.

Sorry that last sentence should read aren't too difficult. But I'd definately start with the tps.

Test AND adjust your throttle position sensor. On a 1990, it IS adjustable.

Start there.