[rickcdewitt]

Another thing comes to mind if the truck had a carrier bearing driveshaft previously(plus the fact it has a new drivetrain with output possiblyin a new location). You want the working angle of your u joints to be equal while going down the highway.. Your rear pinion was not angled correctly for a non carrier driveshaft.for leaf springs that means having the pinion a degree or two lower than the trans output so it rises under load. A cheap magnetic base degree measuring unit will let you check both ends with the driveshaft out on the yoke and trans to compare and adjust with a shim in the back or reweld the perches