Shake a leg...or truck
 

So i was coming home on the highway last week doing 65mph and noticed that there was a great amount of vibration in the truck, '82 C30 dually, bad enough that the dash was squeaking because it was moving back and forth so quickly. But i didn't have any vibration in the steering wheel. It only happened above 60mph, however i have now noticed vibration at 45mph as well. So long story short i figured it was the carrier bearing and after some inspection of the u-joints decided to replace both the carrier bearing and all three u-joints. This was done and after reinstallation i still have the exact same problem. I'm trying to avoid having to take the drive shafts in for balancing and i seem to remember not having this problem until i hit a curb with the back passenger tire a couple weeks ago. Any suggestions? It just seems odd to me that drive shaft would all of a sudden go unbalanced. Could hitting the curb have unbalanced the drive shaft? I don't see how. Thanks!

Re: Shake a leg...or truck
 

Sounds to me like you could have slipped belts in the tire you curb checked.

Lift the tire you hit and spin it to see if you have a knot in that tire.

Re: Shake a leg...or truck
 

Check your rims for lost weights or mud packed in places.

Re: Shake a leg...or truck
 

or a bubble on the inside of the tires

Re: Shake a leg...or truck
 

Also check the pinion bearing. Had a Suburban loosen the pinion nut once. WOW??

Re: Shake a leg...or truck
 

It could be you knocked a weight off the wheel or bent the wheel,Or if you hit it hard enough could have bent a axle shaft.

Re: Shake a leg...or truck
 

Sorry for not commenting earlier, i work at sea and had to go to work a few days after i posted this. As you can imagine i usually have more important things to do, like spending time with family, than working on my truck before leaving so didn't get much time to trouble shoot until now. Anyway, I removed both of the rear driver side tires and both have nice big bulges in them under the tread at one point. I'm guessing this is a result of the plies coming apart. So I will be going to get two new tires. My plan is to swap the two old front tires to the back with the other two good old tires and put the new ones on the front. How does that sound to everyone? I know matching tires on the rear of a dually is important. Thanks for the help everyone!

Re: Shake a leg...or truck
 

That's exactly what I would do. Sounds like you found your problem, let us know how it works.