Differential complete

A complete differential replaces the central gear assembly as a complete unit. Depending on the version, it includes the differential case, crown wheel and pinion, differential pinion and side gears, tapered roller bearings and, where applicable, a locking mechanism. Always check the scope of supply: drive flanges, differential lock actuators and seals are not automatically included. In MAN and Mercedes trucks, buses and vans, a correctly selected and adjusted unit prevents recurring driveline noise, overheating and premature gear damage.

Always identify parts using the vehicle's chassis number, together with the axle code and the identification plate on the fitted axle. Visual comparison or selection based solely on the model name is never sufficient. Models such as MAN TGS, Mercedes Actros or Sprinter are available with different axle load ratings, flange connections and gear ratios. Engine families such as MAN D26 and Mercedes OM 471 help determine the torque load, but do not identify the correct differential on their own.

Distinguish between open differentials, versions with a selectable cross-axle differential lock and, on driven tandem axles, designs with a separate inter-axle differential. Also check whether the axle has a single final reduction or planetary hub reductions. The ratio between the number of teeth on the crown wheel and pinion determines the central reduction; with hub reduction, the wheel-end gearing also contributes to the overall ratio. Mismatched overall axle ratios cause driveline wind-up and damage on coupled driven axles.

Compare half-shaft splines, flange diameter, bolt pattern, bearing seats and mounting faces. Hardened steel gears and precision-fit tapered roller bearings require version-specific tolerances for gear backlash, pinion depth and bearing preload. There are no universal adjustment values: use the workshop data for the relevant axle code.

Whining under load or when coasting may indicate an incorrect contact pattern between the crown wheel and pinion. A speed-dependent humming noise may come from pinion bearings, differential bearings or wheel bearings. Clunks during load changes can also be caused by worn propshaft universal joints or half-shaft splines. Rule out these causes before replacing the complete differential.

1. If safe to do so, carry out a road test and compare noises under power, on overrun and when cornering. If necessary, use electronic listening equipment to locate the source of vibration.
2. Check the level and condition of the specified gear oil for the driven axle. Inspect the drained oil and magnetic plug for metal particles; flakes or tooth fragments require further dismantling.
3. Check flange play with a dial indicator and inspect the pinion oil seals and axle breather. A blocked breather can cause leaks even if the gear set is not defective.
4. Where the gears are accessible, measure gear backlash at several crown wheel positions using a dial indicator. Assess the contact pattern with gear marking compound using the specified loading method.
5. For pneumatically operated differential locks, check the supply pressure with a pressure gauge, the lines for leaks and the actuator movement against the manufacturer's specifications. Also verify the position feedback.

In cases of broken teeth, severe pitting or damaged bearing seats, replacing the complete unit is often more cost-effective than repairing individual components. The crown wheel and pinion form a matched set; do not combine unmatched individual gears. Before installation, check the axle housing, mating surfaces and half-shafts for consequential damage.

Remove residual wear debris from the axle housing and, where fitted, from connected lubrication cavities and hub reductions. Fit the specified new seals and locking devices. Observe the tightening torques and do not alter the pinion nut setting on a pre-adjusted unit without following the adjustment procedure, as this may change the bearing preload. Fill with the correct gear oil carrying the manufacturer's approval and check for leaks, temperature and differential lock operation after the road test. Braem's technical support can help confirm axle identification and the scope of supply in advance.