Gasket

Seals in a driven rear axle keep transmission oil inside the differential housing, hub reductions and wheel hubs, while keeping dirt, water and brake dust away from the bearings and gear teeth. These seals include radial shaft seals, hub seals, pinion seals, axle shaft seals, O-rings, sealing rings and differential cover gaskets. Even a minor leak on a MAN TGL, TGS, TGX or Mercedes Atego, Actros, Arocs or Econic can quickly lead to an insufficient oil level, overheated rolling bearings and damage to the crown wheel, pinion or planetary hub reduction. Seals must always be selected using the vehicle chassis number. Visual comparison or selection based solely on the model name is never sufficient.

The correct seal depends on the axle type, the presence of hub reduction, the hub design and the axle load. Rear axles from MAN F2000, TGA, TGM, TGS, TGX and TG3 may use different seals, installation positions and running surfaces than axles in Mercedes SK, Axor, Actros or Arocs. Seals on buses such as the MAN Lion’s City, Lion’s Coach, Mercedes Citaro and Tourismo, and Neoplan Cityliner or Tourliner are also matched to specific hub and axle configurations. Vans such as the MAN TGE and Mercedes Sprinter also often feature a different hub design with different axle diameters and sealing lip geometries.

Radial shaft seals generally consist of a steel or rubber outer casing, an elastomer sealing lip and a garter spring that maintains controlled radial preload on the running surface. Depending on the transmission oil temperature, circumferential speed and degree of contamination, NBR, ACM or FKM elastomers are used. FKM seals offer better resistance to elevated temperatures and aggressive oil additives, but do not restore worn shaft or hub running surfaces. Therefore, always check the fit, shaft diameter, seal width and direction of rotation of any hydrodynamic sealing grooves.

Oil around the brake drum, brake disc, wheel rim or wheel bolts often indicates a leaking hub seal. Oil at the propshaft flange suggests a pinion seal or flange running surface issue. Leakage around the differential cover may be caused by a hardened gasket, corrosion on the sealing surface or insufficient bolt preload. Also check for oil traces at the axle shaft flange, as a defective O-ring or damaged flange fit often causes a slow but persistent leak there.

First clean the axle housing thoroughly and locate the source after a test drive or brief operation on the lift. Check the oil level and inspect the transmission oil for metal particles, a burnt smell or water emulsion. Measure the radial and axial play of the wheel hub using a dial indicator; excessive play loads the sealing lip eccentrically and can quickly cause a new seal to leak again. Then inspect the running surface for grooves, corrosion pits, blue discolouration or a perceptible wear ridge. A new seal on a damaged running surface is not a lasting repair; where permitted, use a repair sleeve or replace the relevant flange, hub or axle component.

Dismantling hub seals requires careful handling of wheel bearings, spacer rings and locknuts. Always replace deformed locking rings, damaged O-rings and contaminated bearing grease or oil seals. Press a radial shaft seal in only on the outer casing using a suitable installation tool; impact loading on the sealing lip or garter spring causes immediate damage. Lightly lubricate the sealing lip with the specified transmission oil and install it squarely in the bore, without folding over the lip.

After installation, fill the rear axle with the specified oil grade and check again for leakage after a test drive. In case of recurring issues, inspect the hub bearings, breather and axle ventilation: a blocked breather increases internal pressure and can force even correctly installed seals out of their seats. Technically verified parts selection and rapid availability support repairs with minimal downtime.