I have a rebuilt 4L60E trans (rebuilt Aug. 2010) that I am having issues with. My problems started last week when I took off from a stop at about half throttle, when the Trans shifted to second gear the rear end made a loud pop (felt and sounded like the rear end broke) and then the Trans would rev like it was in neutral. The next couple of times the Trans did fine. I drove it for a couple of days without a problem until today. When the trans shifted into 2nd today, I got the loud pop and the rev like it was in neutral. The difference today is it now revs in OD and Drive. I have to pull it into 1st to get the car to move and then I can shift into 2nd manually without any problems. It appears to do fine if I manually shift. I have checked the fluid Any ideas?

 

Can anyone tell me what is bypassed when shifting in manual mode? When I shift in manual mode at any speed from 1st to 2nd, it shifts fine; either barking the tires or leaving a pair of marks several feel long. Now when I let the trans automaticly shift, even at light throttle the trans makes a loud pop going from 1st to 2nd and it's like it jumps into neutral. Even after coming to a stop, the motor will just rev until I pull the shifter into 2nd and then it will grab.

 

When I come to a stop light in D or OD, the car downshifts like it should but when it downshifts into first at a stop, the motor will just rev. If I put the trans into 2nd, the car will take off in 1st and shift into 2nd like normal. I don't know enough about electronic transmissions to make a determination of the problem. Could it be the PCM going bad? Maybe wiring? I would appreciate any input.