Suddenly have a vibration at 60 and above, but only when on the throttle.

I don't know if original poster found his problem. I replaced the carrier bearing and rear u joints. It seemed way better. Started acting up but not as bad. I replaced the u joint on the other side by the transmission. This seemed to have solved the problem. I think next time if this ever happens to me, I would just drop the whole drive shaft and take it to a drive shaft shop. When I had a shop test it out at a shop, they thought there was not really much play in any of the drive shafts. However, replacement of them took care of problem. I should have just dropped the drive shaft and driven in 4-hi to begin with.