94 jeep grand cherokee

It sounds like you either have an Electrical Issue with the PCM or your Band is slipping and you are looking at a rebuild sometime soon.

check the trans fluid smell it to see if it smells burnt the goveror may be bad or it may need serviced

If the transmission will not go into gear or has trouble finding gears and has the proper amount of fluid, the shifting linkage could be bent or misaligned, especially on automatic models. The linkage can be found on the driver side of the transmission, toward the top of the unit. Inspect it to make sure the components aren't bent or broken and have someone shift the Grand Cherokee while you watch from underneath. Most times, only minor adjustments are necessary.
Also, check Torque Converter and scanned the TCM (Trans Control Module) to know if some fault code is stored there.

Check trans fluid level first. Does it react the same in Drive?

sounds like you have 1 of 2 problems either your TPS ( Throttle position sensor) or idle are control valve

Have a code check done and see if speed sensor or controller is working properly. if bought from a dealer, get it back there asap...they can't sell it in that condition!!...No test drive before you ploped down your money?

yes

Check transmission fluid levels,,replace lost fluid as needed,,,if this does not work,,take the car to a mechanic,,,sorry to say,,this kind of problem almost alway's requires a transmission mechanic to repair.

Hi renjay, is your jeep trans an AW-4 or a 46RH? The simple things to check here without getting to the internals are as follows; check your oil level,filter etc. check the throttle linkage adjustment,check the trans shift adjustment also have the TCM tested, the TCM (transmission control module) used with the AW-4 has a self diagnostic program compatible with the DRB II scan tool.The tester will identify faults in the electrical control system it will help determine if the problem is electrical or mechanical, after this it tends to become internal and we can adress that issue if it arises,hope this helps,good luck and let me know how you make out or drop me a line if you have any questions,take care

its most likely the transmission i have a 96 jeep grand cherokee laredo 12 yrs old ..it went about 3 months ago.i would take off at normall speed and it would rev. to about 3,000 RPMS and then the gear would catch ,and give u wiplash.lol but then it got worse. it would be fine taking off then while i was driving ,,i would be going any speed but wen i got up to speed it would start reving high [the gear was sliping] and i had to get it rebult it was like $3'000 grand plus