1999 4 Door 4WD
The Napa site pulls up four different Sized Axle Bearings . I guess this my be for both the 8.5 and the 7 5/8ths but how the heck do you buy parts before starting the job?

Need to do Pinion Bearings and might as well do the axles too .. If the Pinion Bearings were Lube Starved from the P.O. I'm sure the Axles were dry too.
Just can't get a grip on the proper part numbers for the axles The I.D.'s and O.D.'s on the bearings they show for the axle are all different. I didn't try putting in the VIN number, that might help.

 

You will have the 7.625" rear axle.

Napa carries a rear axle service kit for the differential & pinion under PNs BK 3353975 & BK 3353974. You would have to talk with them to figure out the difference.

Then there are some options in terms of wheel bearings for the rear axle. There are the repair bearings which are one piece and move the lip seal to a new portion of the axle shaft to help seal things up better. And there are the stock replacements. The people at the counter should be able to help you out here.

 

That's about where I am with this.
I have an account with NAPA so I can get on there website and call up my specific vehicle. It is just they give me a handful of options that I don't think I can answer until I pull the parts out of my axle.
Stock replacements are fine. The car only has 100K on it. The seals are dry, Just want to replace while it's open. My experience tells me that if the rear hasn't been starved of lube, seals do their job up until about 300K miles.

Also on this Blazer, it looks like the Sway bar has to be removed to get the Ham out of the Casing.

 

Once you restrict it down to the 7.625" rear, all options should "fit". You just have to decide which direction to go in with your rebuild and select the parts accordingly. Again, the counter people, in my experience, will have good recommendations.

Do you have play in the bearings that are in there now? Or do you just want to rebuild it to know it's good? If you aren't experiencing any problems/noises, I would be more inclined to refill it and see how things go...

 

Yeah, I tried cheating and hoping.. I snugged the Pinion Nut a bit and topped off teh Lube.. Slightly overfilled it actually.
There's about 1/8" of up down side to side play in the Pinion/yoke. and it's a little noisey.
So the true mission is to get the pinion out and replace the Races and bearings on the pinion. For the little money and little added time (the axles are slid out a bit anyway), I figured it was insurance to do the Axle Bearings too. It's just a few pulls with a slide hammer.

 

It definitely sounds like it is in need of some help! Hopefully the gears have not been adversely affected by the play.

 

That's what I'm a think'n. I hope the Ring and pinion are not too beat.