Allis Model C - Pinnion Shaft Inner Lip Seal

I know the axel seal is installed to seal pressure, so I would think the pinnion seal needs to relieve pressure.

Forgot to take notice when I did the tear-down.

This is not always true in every case. There are times when you want a lip seal to relive pressure. For example, when you have a gearbox that gets very hot if there isn't at least one seal that relieves pressure the lips can blow out or the pressure increase can cause the lips to wear prematurely since the seal self-energizes under pressure.

Elastomeric seals would be more prone to this since they seal better. On the other hand leather seals probably aren't gas tight.

Bottomline, the final drive probably doesn't get hot during operation so there is no need to worry about traping pressure. It's more desirable to have a drip/leak free final drive.

Thanks again, Steve