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
On a tandem drive truck, the forward-rear axle contains an inter-axle differential, often called the power divider. It splits torque between the two drive axles and lets them turn at slightly different speeds, for example with uneven tire wear.
An inter-axle differential lock, controlled from the cab, locks the two axles together for low-traction conditions. Misuse of the lock, or mismatched tires, can damage the power divider.
Common signs
- Noise or clunk from the forward-rear axle
- Problems with the inter-axle lock engaging or releasing
- Overheating or lube loss at the forward-rear carrier
- Failure after spinning tires with the lock engaged
What the work usually involves
- Check the air-operated lock and shift components
- Inspect and rebuild the power divider and through-shaft components
- Confirm tire size matching across both drive axles
- Lube service per the axle manufacturer
Steps vary by vehicle and component design. Values and procedures come from the manufacturer's service information.
Vehicles this applies to
Class 7–8 tandem-axle tractors, dump trucks and vocational trucks.
Key terms
Tandem drive axle
Two driven rear axles on a heavy truck, the forward-rear and rear-rear axles, which share the load and the driving torque. Common on Class 8 tractors, dump trucks and vocational trucks.
Inter-axle differential
A differential, usually built into the forward-rear axle of a tandem, that splits torque between the two drive axles and lets them turn at slightly different speeds. Many designs include a driver-controlled lock for low-traction conditions.
Power divider
Common shop term for the inter-axle differential assembly on a tandem drive axle. Power divider wear or damage is a frequent tandem-axle repair.
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.