A vibration or a whine at highway speed could come from many places between the transmission and the tires. Finding it means working through the driveline in order, not replacing the most likely part and hoping. RDI Power diagnoses and repairs complete drivelines at our Brooksville shop on diesel pickups, medium-duty trucks, tractors, buses and motorhomes.
What we mean by driveline
Every component that carries power after the transmission:
- Transfer case on 4x4 pickups and some medium-duty trucks
- Driveshafts and their U-joints and bearings; see driveshaft repair
- Differentials: ring and pinion gears, carrier bearings and pinion seals
- Axle shafts, hubs and wheel bearings
- Interaxle differential on tandem-drive tractors, which splits power between the 2 drive axles
Diagnosing a vibration by method
Different components turn at different speeds, so the speed at which a vibration appears points to its source:
- Engine speed related: changes with rpm even when parked or in neutral. Points to the engine, accessories, flywheel or clutch.
- Driveshaft speed related: changes with road speed and is worse under load or coast. Points to driveshafts, U-joints, angles or the pinion.
- Tire speed related: changes with road speed regardless of load. Points to tires, wheels, hubs or brake drums and rotors.
We road test the truck, note where the vibration appears and disappears, and then inspect the components in that group. Driveline angles and working angles get measured when geometry is suspect, especially after suspension work or ride height changes.
Transfer cases and 4x4 systems
Transfer cases wear their chains, bearings and shift mechanisms, and their fluid breaks down. Symptoms include grinding from the transfer case, a clunk when shifting in or out of 4WD, a whine that changes with speed, and fluid leaks at the output seals. Some binding in tight turns is normal for part-time 4WD on dry pavement; noise and leaks are not. Front hub and axle engagement systems on 4x4 pickups also fail, leaving 4WD that will not engage.
Differentials and axles
Whine on acceleration or deceleration, a clunk on throttle changes, fluid seeping at the pinion seal or axle seals, and gear oil on the inside of a wheel are all signs. Gear oil that has been run low, contaminated with water or overheated by towing shortens gear and bearing life quickly. We inspect the fluid, check pinion bearing play and backlash where needed, and repair seals, bearings or gear sets.
Heavy trucks: tandem drives
On tandem-drive tractors, the interaxle differential lets the 2 drive axles turn at slightly different speeds. Locking it on dry pavement, mismatched tire sizes between the axles or low gear oil can damage it. Wheel end bearings and seals on drive and trailer axles need regular inspection, and a leaking wheel seal can contaminate brake linings. Matched tire diameters on drive axles matter here, which ties into tire service.
Driveline repairs
- Driveline angle correction with shims or ride height adjustment
- Transfer case service, seals or rebuild
- Differential fluid service, pinion and axle seals, bearings and gear sets
- Wheel bearing and hub replacement, and wheel seal repair
- Interaxle differential repair on tandem drives
Some complaints that feel like driveline trouble start in the transmission; see transmission repair and rebuild. Takeoff shudder can also be the clutch; see clutch repair.
If your truck has a new vibration, whine or clunk, note the speed where it starts and stops, then bring it in. That detail cuts the diagnosis time.