Vibration at 55mph+

[Z.m4v]

I have a 1996 xj, 4.0 2wd aw4. I recently swapped in another 2wd aw4 from a 2000 xj. Everything transmission wise is running smooth however i have noticed a concerning vibration and howling noise anywhere passed 55 mph. At first I suspected U joints and replaced both driveshaft u joints with spicer joints, I also replaced both wheel bearings and wheel seals. I have greased the slip yoke and checked trans mount.

My guess at this point leads me to suspect a driveline unbalance of sorts, the donor transmission (2000 aw4 2wd) came with a slip yoke, but I opted to just reuse the slip yoke from the 1996 aw4 2wd as it was still connected to the drive shaft i was reusing. I'm wondering if there is a slight difference in play on the slip yokes due to age/ year or something of that sort, if it is unbalanced, I also dropped the driveshaft itself but unsure if it was enough to unbalance it.

My next options were to swap the 96 slip yoke for the 2000 but I'd like some advice if applicable

Video here:

Worth mentioning that I have stock muffler so the low growl on coasting is not an exhaust note but part of the noise I am describing.

 

[Unclewolverine]

No, you were right to leave the slip yolk on because they are balanced to the shaft. It's elsewhere in the driveline.

 

[Z.m4v]

No, you were right to leave the slip yolk on because they are balanced to the shaft. It's elsewhere in the driveline.

It's possible that I put it back on the wrong way when I did the u joint at the back of trans, is it worth taking it back out and flipping it 180⁰

 

[Unclewolverine]

It's possible that I put it back on the wrong way when I did the u joint at the back of trans, is it worth taking it back out and flipping it 180⁰

Very much so. That's probably it.

 

[RCP Phx]

It's possible, but not very likely!

 

[Z.m4v]

Well it was for sure out of balance, I went out and got 2 hose clamps to put on each end of the shaft as a diagnostic tool really, and it eliminated the problem completely