Rearend Vibration

[chaztruett]

Gentlemen, ladies; First post / question after trolling the site for over a year now while looking for a truck. Wonderful site, thank you!

Brought a 68 home from NC and noticed I have a vibration from rear. I get the "roar" in the cab. (I have read ever vibration thread I could find) The vibration comes in about 30 mph + and is speed related as the frequency increases with speed. I put the truck on my lift and ran it at 40 mph and you can actually see the vibration come and go at the left tire. I swapped tires to make sure and it is not a wheel or tire. I do hear some metal noise probably from left bearing. I am not seeing / nor hearing anything strange at drive shaft or rear chunk.

Could a bad bearing cause a rhythmic vibration like this? U joint?

There seems to be a lot of lash in the rearend, not sure though? You can turn the tire about 15 degrees without engaging the rearend gears. Is that normal?

Previous owner had swapped axles sometime in past so not sure of condition nor correctness there.

Thoughts and suggestions appreciated.

Thanks in advance!

tt