my brand new built 4l65E is doing this jerking thing of the line. The first 30 minutes of driving does not produce the jerking problem. This is all happening with the trany in drive. I'm not sure if it has anything to do with cold or hot situations. also, i've noticed that once it starts doing it, if i manually put the trany in low 1 and take off......it doesn't do the jerking thing. only in drive. from a dead stop. it almost feels like it's in 2nd gear at stop and it down shifts only after I apply throttle to take off. The trany builder said to put some friction modifier in to see if it stops the problem. I did that today. after 30 minutes or so of regular driving, it started jerking from a dead stop again. I don't know if it takes a longer period to work its way through the trany or not. I just put it in and did a test run. anybody....help ......please.

 

Could it be the band not releasing fully?

 

what causes that in a new built trany?

 

Friction modifying agents are not necessary in a properly built 4L60E.

You need to get a scanner on it to verify that the correct gear is being commanded. Then, if no anomalies are present take it back to the builder and let him diagnose it.

The reason a band would stay applied is the servo was not assembled properly. But I don't suspect that. I suspect a cross leak in the input drum assembly.

Good Luck.

g