The other day driving down i95 my rear driveshaft broke at the yoke and fell(well flew) off. I had it replaced , balanced, and added stronger u joints. Now at about 25 mpg the truck vibrates like I'm going over rumble strips. I took it back to get rebalanced and still same stuff. Between 25-45 it vibrates like crazy!! My truck is on an 8" lift on 37's. could I have broke something else when the driveshaft broke off?

 

Are you sure that you did not reinstall out of phase?

 

It sure sounds like a mis-alignment between the transfer case and the differential. Just to be on the safe side I would put it on jack stands and while tranny is in neutral turn the rear wheels while looking at the alignment. If it didn't vibrate before the drive shaft flew out, then it is possible that it could have affected the rear end by slightly shifting the shackles. Eight inch lift with 37's is setting up pretty high. You must be a "rock crawler or a mud slinger" I have done quite a bit of that with a lifted CJ5 on 38 Super Swampers, now I am too old and my ole spine just can't take the rattling anymore. Anyway, good luck.

 

Perhaps you bent a flange that you didn't replace. I'd put it on a lift (wheels free) and run it slowly in gear and watch the axle flanges and drive shaft for odd behavior.