Vibration at highway speeds

[m235boy]

UPDATE: Center support bearing was replaced and vibrations gone

Shop assumed it was good but it was slightly loose. Replaced and all good. No markings on the diff (so paint dots at all) so there were no special balancing bolts/washers required.

[CHE///MIST3]

Originally Posted by m235boy

UPDATE: Center support bearing was replaced and vibrations gone

Shop assumed it was good but it was slightly loose. Replaced and all good. No markings on the diff (so paint dots at all) so there were no special balancing bolts/washers required.

That's great news that you found the culprit! Did your driveshaft rebuild company replace the center bearing after the rebuild the first time, or were you still on the original? From my understanding that support bearing can only be changed out when the shaft is taken apart.

GM

[m235boy]

Originally Posted by CHE///MIST3

That's great news that you found the culprit! Did your driveshaft rebuild company replace the center bearing after the rebuild the first time, or were you still on the original? From my understanding that support bearing can only be changed out when the shaft is taken apart.

GM

It was deemed to be "fine" by the driveshaft rebuild company when they initially took it in, changing only the u-joint and cv joint. So yes it was still on the original center bearing.

Obviously something was not right so they replaced the center bearing the 2nd time around and re-balanced. And yes to install the CSB the driveshaft needs to split in half. Maybe upon re-assembling it the 1st time the CSB was not put back properly and forcing it made it loose or it was just weak and needed to be refreshed anyway.

[CHE///MIST3]

Update: still no clues in which way to go from the folks that rebuilt the shaft or did the work...I wouldn't expect it either since my case seems to be so bizarre.

Anyways, I fixed the problem by upping the 4 gram weight to 6 grams. Actually 6 grams seems to be a little bit more like what the balancing washers would weigh given the photos and the size of my diff flange bolts. I can drive well beyond 1XX and the feels smooth and mostly quiet, no more drone or vibration...my tires are close to needing replacement so that will make things even more quiet and smooth.

I guess my diff output shaft was balanced with the driveshaft at the factory? I'll never know.

GM