When inspecting a rear differential for leaks, which seal should be checked along with the axle seals and cover gasket?

• A. Pinion seal
• B. Vent seal
• C. Output shaft seal
• D. Ring gear seal

Answer: (A)

When checking a rear differential for leaks, the seal at the front of the differential where the driveshaft meets the pinion gear is the one to inspect alongside the axle seals and the cover gasket. This pinion seal keeps the gear oil that lubricates the ring and pinion inside the housing. If it wears or fails, oil can seep out around the driveshaft yoke, often appearing as a leak at the front lower area of the differential. The vent seal is a breather, not a primary oil-sealing surface, so a clogged or failed vent is not a typical source of external leaks. Terms like ring gear seal or output shaft seal aren’t the standard exterior leak points in this context, so the pinion seal is the most relevant additional seal to check.