not so good vibrations

So i swapped an 8.8 in my 1990 cherokee 4x4 np242 with a H&T and all was well till i broke a U-joint wheeling last week.

It was probably the mildest break ever just romping on it a little hard and it broke backing up.

Anyways i had a spare shaft and threw that in it and started geting Vibrations at 26 MPH but they would go away around 35. I just chalked it up to being an out of balance shaft, I replaced the universals in my original shaft and put it back in.

But the vibes are still there 26MPH on the nose, i figured i must have bent the output shaft or something terrible so i pulled the shaft again and put the jeep in drive and watched the output shaft spin and it looks perfectly centered to me.
WTF is going on?

So pulled the rear DS out and drove in FWD to work a few days... NO vibes at all, re-inspected the DS and it looks fine

Im about to just put it back in and drive it, the GF says its like a massage :guitar: :greensmok