I just did my u-joints about 2 weeks ago, and all seemed well (besides that clunking at the pinion, and that turned out to be nothing big) anyways, I was going to down the highway and at about 60mph I get this wicked vibration, all through the truck. Would a backwards drive shaft cause anything? It's a balanced aluminum driveshaft so you would think no. Could the u-joints have gone bad? I just noticed it for the first time a couple of days ago.