Hi I have a 1994 caprice. the rear end has been making a slight noise at highway speeds for quite some time I'm certain it is the passenger side bearing, probably the outer(noise goes away when I veer off to the right). Anyway the car just began to leak some diff fluid on the back of the tire and rotor it seeps out a ounce or two a day while parked. I've kept it topped off so I dont burn it up. Is this from the bearing or is it from a seal, or both? I'll probably take it in for service(since I have very little experience with Differentials) unless it's a easy fix. Would it be a good idea while its apart to change out the stock 3.08 gears for some 3.73's also swap the current open carrier to a posi? any ideas on cost new used etc?? worthwhile?? If axles are bad just replace the whole rear end?? Thanks for all input!!

Hi I have a 1994 caprice. the rear end has been making a slight noise at highway speeds for quite some time I'm certain it is the passenger side bearing, probably the outer(noise goes away when I veer off to the right). Anyway the car just began to leak some diff fluid on the back of the tire and rotor it seeps out a ounce or two a day while parked. I've kept it topped off so I dont burn it up. Is this from the bearing or is it from a seal, or both? I'll probably take it in for service(since I have very little experience with Differentials) unless it's a easy fix. Would it be a good idea while its apart to change out the stock 3.08 gears for some 3.73's also swap the current open carrier to a posi? any ideas on cost new used etc?? worthwhile?? If axles are bad just replace the whole rear end?? Thanks for all input!!

Sounds like a rear axle seal is shot, while it is apart, replace the bearings and seal on the opposite side also.
It is not a difficult job but the bearings might have to be pressed on which would require you to take the axles to a auto machine shop.
The gear change is up to you but setting up a rear is not for beginners IMO
You will also need to replace rear pads because they are probably saturated with 90Wt

The bearings are not pressed on these axles.
From your descripion I would go ahead and prepar for the axle shaft to be badly grooved because the bearing is shot, which is what took out the seal.

In minor cases you can get a "bearing saver" bearing that relocates the bearing slightly so you can reuse a grooved axle. Wont know if that will work till you get it apart.

As said gear setup is fairly involved, most guys I know who are comfortable assembling and engine wont assemble an axle.

with the bearing bad it is quite possible that the axle has damage where the bearing rides...a scrap yard should have an axle for you at a good price...

replacing both seals/bearing is the norm ...brake/pads shoes that have 80-90wt oil on them will require replacement...the brakes will tend to grab ...with this oil on then not safe...

replacing the rear diff to another is a lot more involved than what you need done...