seal holds oil and not grease?

The wheel seal is supposed to fit very tight in the wheel assembly and protects the wheel bearings from dirt, water, and other debris that can cause damage. If a wheel seal is damaged or falls off, it will damage the wheel bearings as well rather quickly, so it's vital to have this fixed as soon as possible.

The warning sign on s-cam wear is the shoes starting to stick out of the drums on the inside and wearing unevenly (more wear on the bottom than the top shoe). The worn parts put more pressure on the inside (axle side, not wheel side) surfaces, wearing the drum into a bell shape.

Remove the dial indicator from the inboard end of the cam and rotate it over to the cam head, then manually move the cam head up and down to measure the radial play. If the radial play is 0.030 of an inch or more, the cam bushing or camshaft is worn and needs to be replaced.

The purpose of the axle seal is to keep transmission fluid from leaking. Depending on the size of the leak, it may be okay to drive with a leaking axle seal, but not for very long. One of the more common signs the axle seal is leaking is oil drops below your vehicle after it has been parked.

The classic sounds of a bad wheel bearing are cyclic chirping, squealing and/or growling noise. You can also tell that the sound is related to wheel bearings if it changes in proportion to vehicle speed. The sound can get worse with every turn, or it can disappear momentarily.