i have had my 4.10s for about 7 months now and no vibration what-so-ever, where exactly are u getting the vibration from and is it when u get on it or all the time?
I had vibration before installing 4.10's around 60mph and the 4.10's moved it into the 50 mph range. The drive shaft had to be changed as it's run-out exceeded 0.010" right at the u-joint flange near the trans. I could feel the vibration in the floor board and seat. I don't know if it was caused by a combination of the engine harmonics at that speed with it being in 5th gear as well as slight exhaust drone but it was less after the drive shaft change. Still not completely gone. Incidentally, I have no vibration at 60 mph since changing back to stock 3.55's, so the drive shaft had to cure some of the problem. Still have very minimal vibration at 50 in 5th. Just my opinion but I think these engines have a slight harmonic problem at certain rpm's.