Manufacturer specifications apply. This page explains concepts only. Torque values, clearances, preload, backlash ranges and procedures vary by axle model and must come from the vehicle or component manufacturer's service information. This directory does not publish repair specifications.
What this service covers
4WD and AWD systems add a transfer case or power transfer unit, a front or rear differential, extra driveshafts and often electronic controls. Each part needs the right fluid and periodic inspection.
This category covers routine service and diagnosis of the system as a whole, including locking hubs, actuators and AWD couplings.
Common signs
- Warning lights for 4WD or AWD
- Shudder or binding in tight turns
- Noises that appear only when 4WD is engaged
- Leaks at differentials, transfer case or power transfer unit
What the work usually involves
- Fluid service for each unit using the specified fluids and additives
- Inspection of driveshafts, U-joints and CV joints
- Testing of hubs, actuators, couplings and sensors
- Verification that tire sizes and wear are matched
Steps vary by vehicle and component design. Values and procedures come from the manufacturer's service information.
Vehicles this applies to
AWD cars, crossovers and SUVs, 4WD pickups and work vans.
Key terms
Limited-slip differential
A differential that resists a speed difference between the two wheels, using clutch packs, cones or special gearing, so more torque reaches the wheel with traction. Some clutch-type units require a specific fluid or friction-modifier additive; follow the manufacturer's fluid specification.
Driveline operating angle
The angle at each U-joint between the two shafts it connects. A standard cross-type U-joint speeds up and slows down slightly within each turn when it operates at an angle; drivelines are designed so these fluctuations cancel out. Allowable angles come from the vehicle and driveline manufacturer.
CV joint articulation
The range of angles through which a constant-velocity joint can work while transmitting smooth, constant speed. Outer joints allow larger angles for steering; inner (plunge) joints also allow the shaft length to change as the suspension moves.
Choosing a shop
- Confirm the shop works on your vehicle class and, for trucks, your axle make.
- Ask what parts they install (new, remanufactured or rebuilt) and what warranty applies.
- Check the listing's verification status and date in this directory.