Having trouble. Put new u-joints and carrier bearing on truck. Had driveline balanced and tires are balanced. But I am getting a vibration from the rearend possibly starting at 30-35 mph and it dies down around 55-60 mph. I can feel it in the seat. No growling noise so I don't think its a bearing. Nothing leaking. Gear oil was about a half quart low. Rearend is a 8.25 open diff truck is 2WD. I've had two mechanics look at it and no real answer. I've had the tires and brake drums off and is still vibrates. HELP!!!! This is driving me nuts.

 

did you center the u-joint on the axle? maybe torqued something too tight or too loose

 

If it didn't vibrate before the U-Joint change then the U-Joint is most likely the problem.

This chart may help. https://dodgeforum.com/forum/1947777-post6.html