The technician carefully balances and aligns the wheels. He takes the truck for a test drive to verify the repair. The truck still has a harsh vibration. It seems to get worse as speed increases. A bent wheel or bad wheel bearing or hub is suspected. After returning to the shop, he measures the run out and checks the play of each wheel. Finding nothing wrong, he carefully checks the roundness of the tires. While doing so on the rear tires, he discovers the cause of the problem. When the lift kit was installed, the operating angle of the rear U-joint was affected. As the drive shaft turns, it hesitates slightly. This hesitation is caused by a binding of the U-joint. The technician informs the owner of the cause and suggests that the lift kits be removed or the drive shaft operating angle be corrected.