This maintenance manual provides detailed instructions for the service and repair of AxleTech International W3H, W4H, W4M, and WDM Series Wet Disc Brakes. These brakes are available in diameters of 330 mm (13 inch), 360 mm (14.2 inch), and 432 mm (17 inch).

Brake Types and Identification

W3H and W4H Series: These are hydraulically actuated friction brakes.
W4M and WDM Series: These are spring-applied, hydraulically released brakes.
Identification: The exact specification is indicated on an identification tag located on the axle housing.

Cooling and Fluid Maintenance

The brakes utilize either sump cooling (where discs are submerged in housing fluid) or forced cooling (using an external pump and reservoir) .

Temperature Limits: Operating temperature must never exceed 250°F (120°C), or internal components will be damaged.
Change Intervals: Coolant should be changed after the first month (200-250 hours) and every six months (3,000 hours) thereafter.
Approved Fluids: Petroleum-base SAE 10W, SAE 20W, or SAE 10W30 are standard. Tractor oil universal (TOU) fluids formulated for wet disc brakes are also recommended.
Hydraulic Fluid: Use only the fluid specified by the vehicle manufacturer to avoid damaging the piston seals.

Safety and Disassembly Highlights

Spring Pressure Warning: For W4M and WDM models, the brake must be caged in a press before disassembly to prevent serious injury from the sudden release of spring pressure. Approximately 20 tons of force is required to cage these brakes.
Disc Inspection: Replace the full disc stack if any disc is worn beyond the specified thickness limits (e.g., 0.167 in / 4.25 mm for 13-inch friction discs) or shows warpage, scoring, or uneven wear .