I need some help. 04 FX4 w/144k miles. Had the transmission replaced recently (would just rev but not go after 2nd gear) with a Jasper unit. Now, intermittently, I get the dreaded drivetrain clunk when accelerating out of a turn. It did not do this prior to the transmission replacement.

The shop that replaced the transmission won't do anything because it only happens once in a while (2-3 times on an average driving day) and they haven't been able to duplicate it. They felt it may be a misfire and charged me for a tuneup and a new COP.

I took the driveshaft off (single driveshaft) and applied the Ford PTFE grease as outlined in one of the Ford TSBs. The driveshaft spline was bone dry. Still experience the clunk which feels like something in the drivetrain slipping then engaging hard.

I don't know what to do next. I spent $3k to have that transmission replaced. Could the new rebuilt tranny be bad ? Should I demand another replacement ? It has a 3yr/100k warranty.

Please help