Hey guys. Quick question here. I had the 3.9 finals installed in my car, and went to reinstall the differential. When I went to pilot the driveshaft to the differential flange, they wouldn't fit. At first I thought there were too many threads on the pinion shaft pertruding past the pinion nut, causing it to hit the driveshaft flange before they would mate up.
After filing down some of the remaining threads, I still was having no success mating the flange. It would walk back and fourth, but not mate together.
Finally, I painted both the nut on the pinion shaft, and the "cup" of the driveshaft flange to check for contact. There was no paint transfer to indicate they were contacting one another.
Finally I put two of the driveshaft bolts in on opposite corners. If I carefully tightened each one equally, I could pull the flanges together. I did not force them, and they are flush.
Has anyone else had troubles re-installing the driveshaft as I have?? The only reason I am questioning myself is the fact that I just had the pinion installed, and my first thought was that It was now sticking out further that before.

 

It's just that tight and accurate of a fit sometimes. If it does pull up flush, then there is no problems.