[Turbo85GMC]

On the rear:

1. Pull off the wheel.
2. Pull off the brake drum.
3. Drain oil from differential.
4. Take off diff cover.
5. Take out bolt that holds in center pin.
6. Take out center pin.
7. Go back to the axle where you took the drum off.
8. Push the axle in.
9. Go back to the diff.
10. Reach in and take the "C" clip off the axle.
11. Go back to the axle where you took the drum off.
12. Pull the axle all the way out.
13. Now you can see the seal.
14. Pry out the seal with a big screwdriver or vice grips.
15. Tap new seal in with a hammer and big socket.
16. Reassemble in reverse order.
17. Do other side.
18. Don't forget to put new oil in the diff.
19. Drive it like you stole it!

Don't know about the front, mine's a 2wd so it's completely different.