The driveshaft carries every pound-foot of torque from the transmission to the axle, and on a diesel that is a lot. It spins fast, flexes as the suspension moves and depends on a few small joints and bearings to do it smoothly. When any of them wears, the truck tells you through squeaks, clunks and vibrations. RDI Power repairs driveshafts in Brooksville, and many driveshaft jobs can be done on site by a mobile technician.
What is in a driveshaft
- Tube: a hollow steel or aluminum shaft, balanced at the factory with small weights.
- U-joints: cross-shaped joints at each end that let the shaft work at an angle. Some have grease fittings, many newer ones are sealed.
- Slip yoke or slip joint: lets the shaft change length as the suspension moves.
- Center support bearing: on 2-piece shafts in long-wheelbase pickups, heavy trucks and many motorhomes, a rubber-mounted bearing supports the middle.
- Yokes and flanges: connect the shaft to the transmission, transfer case and axle.
What the noises mean
| Symptom | Likely cause |
|---|---|
| Squeak at low speed, in rhythm with the wheels | Dry or worn U-joint |
| Clunk when shifting into gear or on throttle changes | U-joint play or worn slip yoke splines |
| Vibration that grows with road speed | Imbalance, a lost balance weight, worn U-joints, bent tube |
| Shudder on takeoff, especially loaded | Center bearing wear or incorrect driveline angles |
| Rust-colored dust around a U-joint cap | Needle bearings failing inside the cap |
Driveshaft inspection
On the lift, we check each U-joint and the slip yoke for play by hand, look for rust dust and missing seals, and inspect the center bearing rubber for cracks and sag. If the vibration has no obvious mechanical cause, we measure driveline angles with an inclinometer and check the shaft for runout and balance. Lifted trucks, lowered trucks and trucks with changed ride height often have angle problems that eat U-joints repeatedly; our driveline repair page covers that bigger picture.
Driveshaft repairs
- U-joint replacement, using greaseable joints where the application allows
- Center support bearing replacement
- Slip yoke replacement and spline lubrication
- Driveshaft balancing after repair, or replacement of a bent or damaged tube
- Correcting angles with shims or ride height adjustment when geometry is the root cause
Driveshafts on RVs and buses
Diesel pusher motorhomes and buses run long driveshafts with center bearings, and they often sit for long stretches between trips. Sitting lets grease dry out and seals harden. Our article on recognizing and preventing failing U-joints in your RV explains what to watch for, and our RV service covers the rest of the chassis.
Keep it greased
Greaseable U-joints and slip yokes need grease at every service, and they wear quickly when they go dry. Our oil and lube service includes every fitting on the driveshaft. On fleet trucks, U-joint condition is part of every PM.
Hear a new squeak or feel a new vibration? Bring the truck in, or ask about a mobile repair at your location, before a worn joint becomes a dropped driveshaft.