Engine Revving/Transmission Disengaging

I have a 1990 Jeep Cherokee. Everything operates fine except when I'm cruising at any speed and the transmission seems to disengage and the motor revs about 500 to 600 rpms higher. The engine and transmission goes back to normal for a moment, then disengages again - no power from the transmission, only the engine revving. There is no jolt or catching with the transmission. I had taken it to AAMCO some time ago and they placed sensors on the transmission and it was fine. I think it may some type of sensor that may be loose, but that is just an uneducated guess. Any help would be greatly appreciated

Low transmission fluid levels or a plugged trans filter can produce such symptoms.

Also, a problem with the transfer case linkage can also produce such issues. Does the same problem occur when the truck is in 4 wheel drive and/or in Low Range?

I'll replace the transmission filter first to see if that produces any results, and then on to the transfer case linkage (which will require a mechanic). I've switched from 2 Wheel Drive, to 4x4 Full Time and 4x4 Part Time and it still produces the same problem.

I agree, it sounds like a fluid level problem. Did the shop remove the T-case from the tranny? Look at the back of the tranny, were the transmission and t-case bolt together, is it wet? This is a prone area for leaks. What sensors did they change? If it is leaking, then I would take it back to the shop and have them remove the t-case and install a new seal. Most seals are a fiber type, but gray RTV will work well if everything is clean.

It turned out to be the Throttle Position Sensor (TPS). I replaced it and my Jeep runs perfect - no misses and plenty of power. Thanks for the tips.