U-JOINTS

U-Joints For Peterbilt Trucks

Universal joints allow the driveshaft to transmit torque through the angular changes that occur as the suspension cycles and the drivetrain flex under load. On a tandem rear axle Peterbilt, there are multiple U-joints across the main driveshaft, the inter-axle shaft, and the axle half-shafts — each one subject to constant cyclic loading at high torque. A worn or failed U-joint causes vibration, clunking, and in catastrophic failure, driveshaft separation — which can be a devastating event at highway speed. We carry U-joint crosses, bearing kits, and complete U-joint assemblies for Peterbilt drivetrain applications.

Frequently asked questions about U-joints

How do I check U-joints for wear on a Peterbilt driveshaft?

With the driveshaft stationary and the transmission in neutral, grip the shaft firmly on each side of a U-joint and attempt to rotate in opposite directions — any rotational lash indicates a worn cross or bearing cups. Also check for axial movement by pushing and pulling the yoke toward the joint — bearing cup looseness in the yoke bores is a sign the cup has spun and damaged the bore. Rust staining bleeding from the bearing cup seals is an early warning sign that the joint is losing lubrication and should be inspected closely.

How often should U-joints be greased on a Peterbilt?

Greaseable U-joints should be lubricated at every PM service — typically every 25,000 miles — using a chassis grease meeting NLGI Grade 2 specifications. Pump grease until fresh grease purges from all four bearing cup seals, confirming all four cups have received lubrication. U-joints that don't purge grease from all four seals may have a blocked passage and should be investigated further. Sealed U-joints without grease fittings are designed for the life of the joint and should be replaced rather than lubricated when they show play.

Can I replace just the U-joint cross and bearing caps without removing the driveshaft?

In some cases, yes — if the yoke bores are in good condition and there's adequate working clearance, U-joint crosses can be replaced in place using snap ring pliers and a U-joint press or suitable press tool. However, on most Class 8 driveshaft applications, removing the shaft for bench work produces a better result and allows inspection of the slip yoke, tube, and yoke flanges that isn't possible with the shaft installed. Given the safety implications of a driveshaft failure, taking the time to do a complete job on a bench is the recommended approach.

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