Leaking axle seals in a '95 GMC 4WD - make wheels hop? Changing seals

[DJJ]

My brother just asked me to help him change the rear axle seals in his '95 (could be a '96 - don't know for sure) GMC Sierra. He said he was told by a mechanic some 5 or 6 years ago that they were leaking, and would eventually cause the wheels to hop during braking. He said it has started to hop, so he thinks it's time to change them.

Can leaky seals cause wheel hop during braking? How? Frankly, I'm skeptical of any connection between the two (bad bearings maybe, but seals?). I don't know if it's an issue of contaminated brake rotors or what. The leak must not be too bad if he can live with it for 5 years.

Is there a website where I can get instructions (and pictures if possible) on how to change these? I've done it once before, but on a 2WD car with drum brakes. Anybody have any experience/tips? What special tools might we need? Thanks.

[mfree]

Grease on braking surfaces will grab.

[Art Eatman]

mfree's correct.

If the rears are drum brakes, it's no big deal.  Disks?  The parking brake hookup is a PITA.

Haven't looked at late-model stuff.  Used to, you just pulled the brake drum off and undid the four nuts holding the axle retainer in place.  Pull axle, replace stuff as needed.

Trouble is, nowadays, among other BS, the axle itself is the inner race of the wheel-bearing.  If that race surface is galled, think $$$$$.

Check a used-book store to see if they have a shop manual.  Otherwise, the shop manuals on sale at car parts stores are plenty good.  AutoZone, etc.  (I like AutoZone; they give Old Farts a 10% discount.)

Art