00-05 Impala 9C1/9C3's don't have HD Transmissions

All they have is a oil cooler for the transmission that loops along with the radiator then goes back, they all have 3.29 gearing with no LSD just traction control, They might have a shift kit to firm up shifts. The transmission is a 4T65-E and it does not have the 4T65-HD as some expect or suggest it has. No wonder police impala transmissions go out when they were in police duty.

The shorter gearing does help it launch better but speeds above 40mph I thought the car was slow. I don't think the car had the 40mph WOT 1st gear lockout issue as most W-body cars have if I remember correctly.