shifting problelms

My 1988 Cherokee with AW4 automatic transmission has started to dowshift unexplainably while just driving at a steady pace. Engine races, then it upshifts again.... I replaced the TPS, and have changed fluid and done a new filter assembly. It seemed better, but that lasted only a couple of days. Is there a critical adjustment for the Throttle Position Sensor? Any ideas? When it shifts normally, it shifts nice and positive, but when it is downshifting automatically it is hard to drive.

Any help will be gratefully received,

Yesway

I had a tps go bad and cause shifting problems, never had to adjust it myself- but there is a procedure: http://www.wagoneers.com/XJ/tech/TPS-adjustment.html
Best of luck

Is there a particular speed where it does this? (like around 45mph?)