Recently rebuilt my tranny. The fluid is full actually over full a little bit and whenever I press the gas down to accelerate hard and it kicks down hard to I think 1st (could be 2nd) it slips bad and than catches itself around 5000RPM. What could cause this slipping? This is the only gear that slips and it only slips when it kicks down hard, it does fine during normal shifting. Thanks

 

Which gear is it? 1st gear usually tops out at about 35-40MPH and 2nd gear will top out at about 70-80MPH. It should be pretty easy to tell.

But if you're going say 25-30MPH and not pressing the gas at all, it would be sitting in either 3rd gear or OD. If you're doing 3rd/4th to 1st WOT drops all the time, it's pretty hard on the transmission. I don't really see the need to floor it when you're cruising at ~30MPH. It's not the greatest habit in the world..

One other thing that's bad for it is overfilling. If your level is over full, that's usually not a good thing.