I had this problem. I tested for it by spraying litium grease on the carrier bearing. That silence it for a while. It was odd because the bearing seal looked fine. So, why would the lithium grease have such an impact?Thanks bob, I need the two mid shaft bearings though not the u joints
When I had the carrier bearing changed, I got my answer. The bearing center was actually loose on the driveshaft. It fell right off. My mechanic had to install the new one with the shop press. After 40,000 miles, still no noise.
So, the noise was caused by the drive shaft spinning within the bearing sleeve. That is why the lithium grease had such immediate, yet short term effect.