Differential housing

The differential housing locates and supports critical components in the final drive. A damaged fit or distorted mounting surface can therefore cause further gear damage, even after tapered roller bearings and seals have been replaced. This category covers the stationary housing in which the drive pinion, crown wheel and rotating differential case containing the differential pinion gears and side gears are mounted. This housing is then installed in the axle housing.

Always identify parts using the vehicle's chassis number, together with the axle identification and original part number. Visual comparison or selection based solely on the model name is never sufficient. Different axle designs are used within ranges such as MAN TGS and TGX or Mercedes Actros, Arocs and Sprinter. Engine power and drive torque influence the axle variant used, but the engine family alone does not determine the correct differential housing.

Check whether the axle has single-reduction final drive or hub reduction, whether a differential lock is fitted and its position in any tandem axle drive arrangement. Key features of these housings include the bearing seats for the drive pinion and differential case, clearance for the differential lock clutch, mounting flanges, sealing surfaces and attachment points to the axle housing.

Depending on the version, cast iron, ductile iron or cast steel is used. Material strength, roundness, coaxiality of the bearing seats and flatness of the mating surfaces determine the load capacity. The lubricating oil compartment is generally vented and is not designed as a pressure vessel; excess pressure is more likely to indicate a blocked axle breather. Only the relevant axle manufacturer's specifications apply to fit tolerances and tightening torques.

Whining under load or during engine braking, clunking when the load changes and metal particles in the gear oil may be associated with incorrect gear alignment. However, they do not prove that the housing is defective. Loose tapered roller bearing rings can wear their seats out of shape; cracks may develop around bearing seats or mounting points, and the flange that mounts to the axle housing may become distorted.

1. Before dismantling, check the lubricating oil level, look for leaks and inspect the axle breather. Drain the gear oil into a clean container and inspect the drain plug magnet and sediment for wear particles.
2. Measure gear backlash with a dial indicator at several positions around the crown wheel, with the drive pinion locked. Check the tooth contact pattern using gear marking compound in accordance with the workshop procedure.
3. Clean the removed housing. Measure the bearing bores with a dial bore gauge at several depths and in two perpendicular directions. Check the flatness of the flange that mounts to the axle housing and inspect the sealing surfaces for damage.
4. Inspect suspect areas for cracks. For ferromagnetic housings, have magnetic particle inspection carried out if necessary. Compare all measurements with the rejection limits specified for the axle.

Replace any housing that is cracked or has bearing fits outside tolerance. Repairing a worn bearing seat with retaining compound, centre-punch marks or uncontrolled welding does not restore the original geometry or fatigue strength. Keep matched bearing caps in their original positions and orientations; swapping them indiscriminately can compromise the bearing bore.

During installation, also check the tapered roller bearings, differential pinion shafts, thrust washers and crown wheel fastening. Readjust pinion depth where necessary, bearing preload and gear backlash in accordance with the manufacturer's procedure; the old shims do not guarantee the correct setting after housing replacement. Clean the lubricating oil circuit, use the specified gear oil and check for leaks, noise and temperature after a road test. This prevents residual wear particles or incorrect adjustment from damaging the replacement part again.