Do you mean axle seals?
It depends on the model or, more specifically, if you have one or two piece axles. the easiest way to tell is if the axle hub has a large bolt in the center, if I remember correctly 1-1/2", it is a two piece axle.
The axle seals on the one piece axles are a pain. You have to be able to get to the axle bolts inside the chain case And remove the entire axle. The front isn't too hard but the back is.
The two piece axles, the hardest part is getting the hub to release. It normally takes a couple of bottle jacks up against the frame and a hammer.