zukamini

Hey guys ,had a strange thing happen today driving home from work. after driving for about 5 miles,I came down a slight hill and used only brakes for speed control, I had to stop at bottom of hill for a signal light. when I accelerated ,it took off fine but when it shifted to second ,there was major slipping (barely any forward movement). I pulled over and checked fluid level which was right up and clean. engine was at normal operating temp., I put it back in drive and there was slipping right away,I dropped it into low gear & second and moved forward normally .I pulled into a parking lot and crawled under checking for leaks and loose linkage but all were good. I started it back up and put it in drive and it responded normally , no slipping for the rest of the trip home. I had installed a new TPS a month ago so I checked for loose adjustment bolts and rechecked voltage and resistive values all were within spec. any ideas as to what may have caused this ? 1988 xj limited aw4 trans.4.0 inline 6