Chevy 1500 4x4

SOURCE: 1991 chevy silverado 1500 2-wd leaking oil seals, rear end.

the outer bearings can be driven in using a suitable Very Large socket. Removing the old ones either requires a puller or a cutting torch. I use either depending on the state of the bearings.
when driving new ones in, make sure

1. your socket wont jam in with the bearing
2. you only hit against the outer bearing shell
3. you keep it very straight
4. hit it til you hear a resounding solid clunk as the bearing reaches full insertion.
5. you fit a new oil seal
6. use a block of wood across the oil seal face to protect it as you knock it in - keep it straight!

SOURCE: Rear End in a 2000 silverado moning whenever I turn a corner.

I would suggest a rear differential service. When the fluid breaks down in the rear it doesn't provide the proper lubrication for the rear and you'll hear the "moan". Don't forget to buy and add the limited slip(posi-trac) additive.

As far as the rear end noise, There was a TSB released on GMC light duty trucks that says "Some owners of light duty trucks equipped with automatic transmissions may comment that the vehicle exhibits a clunk noise when ******* between Park and Drive, Park and Reverse, or Drive and Reverse... Whenever there are two or more gears interactin with one another, there must be a certain amount of clearance between those gears in order for the gears to operate properly. This clearance of freeplay (also known as lash) can translate into a clunk noise whenever the gear is loaded and unloaded quickly, or whenever the direction of rotation is reversed." It goes onto say "...Whilse some owners may find the clunk objectionable, this will not adversely affect durability or performance."

SOURCE: instructions on replacing rear axle end oil seals 90 silverado pu

Where's it leakin?

SOURCE: rear end gear ratio

you can count the teeth on the ring gear and divide that # by the tooth count on the pinion. An example is: ring gear 100, pinion 10 ...100divided by 10 is 10, expressed as 10 to one. (fake #) your diff is likely a 3 series such as 3.23 to 1. or a four series such as 4.11 to 1. If you have four wheel drive it is critical to match exactly. if not you can get better performance by changing ratio to something that better fits your needs. 4 series pull loads well, 3 series are better on fuel.(depending upon terrain)

SOURCE: rear end oil capacity and type of rear end oil for '02 chevy 1500

90 weight oil