Hey guys. Newbie here. I have a 97 Silverado 5.7 with 4l60. Just bought a rebuilt trans with upgrades. I put trans in and it slips in first gear and in reverse. Reverse only slips when you go from drive to reverse. Seems to be fine when put in reverse from park. This is the 3rd trans I have bought since October. (2 different builders for 2 different trucks) Not having any luck! Any one have any suggestions on what could be wrong with this trans? Any help would be greatly appreciated!! Thanks!