I have been fighting a problem with my truck haveing a vibration when driving down above 50 MPH. I originally thought it was the tires, so I put 6 new tires on with "Balancing Beads" instead of wheel weights. Did not make much of a difference.

This is what I noticed with the back of the truck up on jackstands placed under the frame so the rear tires can spin. With wheels on, trans in 5th gear, engine idleing the rear axle bounces up and down. I removed all four wheels and bolted up just the drums. I noticed it still bounces up and down, not quite as much as with wheels on. I romoved one drum at a time and found that one was much worse than the other. This was a new drum I installed recently because I had one that seemed to be bent or out of round causing that brake to lock up when aplying brakes when moving slowly. I marked the high spot of the drum by having it turn in 5th gear with the engine idling. I then turned the drum 180 degrees to make sure it was not the axle hub causing the drum to be out of round. The high spot was in the same position on the drum. I returned it to Advance for a "better" Bendix brand. This new one seems to be much better, but the axle still bounces some with this drum being installed. The axle does not bounce at all when I have both drums removed. Both drums have been replaced with ones from Advance. Neither have any indication of being balanced. ie: no weights or cuts to balance.

Has anyone heard of replacement drums not being balanced?

 

Never heard of out of balance drums but have seen worn wheel bearings cause vibration.
It doesn't take much wear at all to cause vibration, you will need a dial indicator to see it.

 

Bearings apear to be good. Hub rotates smoothly. I tightend up the hub nut to 120 ft/lbs (hope that is the right???) I ran truck in gear and showed no noticiable runout on the hub outside edge. All the wheels and tires are slightly out, but I do not believe enough to be a problem. I think some runout of the wheel and more on the tires are normal.