rear axle seal

[Hummie2]

Sounds like your repair guys should find and correct the REAL problems, not just replace the seal and call it fixed! Smell getting into the cabin is definitely bad as CO gets in also and you can't smell that. A plugged vent line was only a thought as it is oftentimes overlooked by many mechanics and will cause seals to fail again shortly. Ofcourse other more serious(expensive) mechanical problems will cause it too fail also.

Don't get used to it! RAISE HELL, because it isn't RIGHT!