Shake a leg...or truck

[lgvl]

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!