A couple days ago I installed a SYE and moved the front driveshaft to the rear. I drove it like this for a few days and was very happy with the lack of vibration on the freeway. I ordered shims for the pinion angle because there was still a very small vibration coming from the rear axle. Now I took the Jeep to a shop to get regear and they also built me a new driveshaft for the rear while it was there. I picked it up today and on the way home I had a very bad vibration, worse then I had with the stock shaft. I'm wondering if this means that the driveshaft is unbalanced, or maybe the new CV joint needs to be broken in, or maybe this is a more serious problem. Any insight is greatly appreciated! Thanks!

 

Sounds like an imbalanced driveshaft to me.
I would throw the old one back on real quick to double check.

 

OR take it BACK to the shop so they can fix what they did wrong.

 

Yeah I'll be taking it back tomorrow, I was just curious if it was maybe something small I didn't think of