'10 e67 with Colorado base tune and t42 tcm. TCM was tuned by Currentperformance as was the wiring. Problem is reverse just drags the engine down to where I cant hold the brakes while in reverse or it will stall almost like the convertor is locked or something. Same thing happens if Im cruising and runs through the gears then come to a stop in d4. itll drag the engine down to about 400 rpms for a few seconds then itll release and idle like normal. Not sure why its doing this. Fluid seems to be the correct level with engine running in park. Trans is new 4l80e stage 2 full auto from Jakes, convertor is CircleD 3600.