The seal is held in as a press/interference fit into the differential housing. Hook it from behind (going in from the side of the seal that the axle slides into) and pull it out with a seal puller or anything else you can get behind it. Often times they can be collapsed with a hammer and chisel to relieve the interference fit tension. Put the chisel on the outer edge of the seal and drive it toward the center of its hole, then you can get a screwdriver behind it and pry it out the rest of the way.

Be careful not to nick other surfaces, protect them with a lot of tape wrapped around them.

Look at the back of the new seal, if there is a small spring fill the cavity that the spring sets in with a SMALL amount of vaseline in a few places, not the entire cavity just a few places. This prevents the spring from jumping out while driving it in place.

Use a pipe, socket or block of wood to go between the new seal and hammer when knocking it into place. Do not strike the seal directly with the hammer.

Polish and lubricate the stub of the axle with gear oil where it contacts the seal before installation.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer