Do i know the transmission is going bad if it starts shifting hard or what?
Here’s a few common 4L60E symptoms:
- slipping, especially in third (3/4 clutch pack fried)
- shuddering (Torque converter taking a dump)
- late harsh 1-2 shifts w dtc p1870 (valve body - can be fixed w/o removing trans)
- no forward movement in Drive but you can move forward in manual low or 2; reverse also works (input sprag failure)
- no movement at all in any position on the shifter (pump failure, stripped input shaft splines or tcase failure if a 4WD)
- loss of reverse, second and fourth gear (sun gear reaction shell failure or rear gear train failure)
The above list is not exhaustive and applies only to the 4L60e. If you have a six speed 6L80, I can give you a similar list applicable to that trans.