I have a 99 silverado short bed with extended cab. Runs a 5.3 with the 4l60e. While driving to work one morning I realized I wasn't hitting all the shifts and was running high Rpms after some research I found my 3-4 clutch packs was burned out and decided to try my hand at rebuilding the transmission. After some time and research I had replaced the clutches and rebuilt the pump. When I reinstalled everything and I get nothing. Barely wants to move forward. No reverse at all and it barely wants to creep forward. Decided something must be wrong so I took it out and redid everything but after install still nothing. So I admitted defeat and got a new transmission. Problem is that it does the exact some thing. No reverse, creeps forward but only with heavy throttle and I can't select low gears. Anyone have a clue what's going on?