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Axle Seal Basics

Axle Seal Basics Inner and Outer

I am replacing my axle seals on my skid steer and am trying to understand the basics. And, I have purchased one set of OEM and plan to purchase the other three sets aftermarket, probably timken.

There is an inner and outer seal.

The outer has a metal frame with a lip; the lip faces toward the tire side of the axle. I have included a few photographs of it.

The inner seal is a rubber/plastic design and also has a metal elastic spring inside the seal.

What is the purpose of each of these seals?

Why is the metal one on the outside?

Why does the metal one not have the metal elastic spring inside the lip?

Any details would be appreciated.


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Re: Axle Seal Basics Inner and Outer

I would think the metal seal has to keep the mud, dirt, and gravel out of the bearing and the inter seal has to seal the oil in. Some seals have the spring and some don't.

Mitch Malcolm

The outer one with the steel outside is for dirt and twine strings the inner is to try to hole the oil in … Its twine strings that make them fail if seen it 1000 times ( my first job was working on Melroe bobcats ) back when the 610 was a state of the art machine … No wonder my knees are shot :)


More lips mean more friction, more heat, and more wear, along with better sealing. The garter spring tends to increase contact pressure from the sealing lip, resulting in better sealing, but again increasing friction.

If I understand it correctly, the outer seal has 2 lips, but no spring, while the inner has one lip and a spring? As the folks have said above, the outer is a dirt seal, while the inner is an oil seal.

The fully coated rubber/plastic inner seal allows the OD to seal better to the housing bore. Sometimes you see a coating of some sort (paint) on the OD of the metal seals, which also helps to seal to the housing bore - it's usually mostly shaved off when you press the seal into the bore.


It seems that the inner seal is also commonly called oil seal.

Is there another name for the outer seal, other than dirt seal?