I had the same problem but the shop told me it was from to much tranny fluid, i was on the interstate, went thru a tunnel at 55mph, went to pick up more speed and it would goto 65, then 75 and it would keep picking up speed but it was taching way to high, i let off the gas to get it to kick in to gear, which it did, then when i hit the gas again it started to slip, i pulled over and called a wrecker, 275.00 later i get it home, drive it off the rollback, and i havent had any trouble since, it only did it that one time, i drive it to work every night and it hasnt slipped yet, but im paranoid to take it on anymore long trips, when i checked the dipstick it was showing more tranny fluid the it suppose to so i had the fluid and filter changed, i hope it isnt something were i have to have the tranny rebuilt! btw its a 98 2.2 auto with 73000 miles..