Ok, my 99 Blazer 4X4 started making a kind of steady roaring noise when you put it in 4 hi . Put it back in 2wd and it gets much quieter. It's already got new wheel bearings.Put it up on jack stands and couldn't really pinpoint it with the wheels off the ground. Wiggled the driveshaft by the front differential and it seemed like there was a lot of slop so I pulled the driveshaft.To my surprise, when I got the driveshaft off there wasn't much slop in it. Sent it up to a mechanic friend of mine and he confirmed my worst fear. The slop was actually in the front differential. I have done just about everything on a car but not any differential work except for swapping a couple out. I'm assuming it's a pinion bearing but haven't actually done one so I'm asking for advice. As I said, I've done about everthing BUT differentials so I'm not a novice.
1. Should I change the bearing and if so will it require special tooling and is it too difficult without having done it before? Also is my assumption about the pinion bearing correct or am I off base ?
2. Should I pull the differential and take it in and have it rebuilt and about how much cash would I be looking at ?
3. Should I just get a used one and throw it in there. Not really crazy about this one since you never really know how long a used one will last.
Hoping someone with more experience in this area can point me in the right direction.

 

There is lots of mesuring work to do for a pinion, unless you are just replacing the bearing and seal. There are many write ups about Ring and Pinion installs (even on Trucks from Powerblock www.speedtv.com)
Tools needed:
Torque wrench
Seal puller
Press (or a shop that can press the bearing on for you)
Gray ATV gasket maker (the heck with the paper one this holds 1,000 x's better)

Parts:
Pinion bearing
Pinion seal
Might as well do the axle seals too
crush sleave (if you want to replace it, it would be a good idea to do so)
Keep the spacers unless they show heavy wear, then make sure you match them for replacement
80-90w gear lube

I did this on a 2002 Durango already. Its not a hard job to do.

If you do go used, get one from a NEWER vehical might be abit more in cost but then you would have one with less miles. Avg. cost of $250 for a used one.

 

Sorry, I don't have alot of time for a detailed post right now as I'm on my way out in 15 minutes.

What I can tell you now is that the front diff is different than any rear diff I've ever done.
Here are a few tools you will need.[align=left]



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J 21551 Output Shaft Bearing Remover
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J 22912-B Pinion Bearing Remover
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J 23907 Slide Hammer
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J 29369-1 Bushing/Bearing Remover•
J 29369-2 Bushing/Bearing Remover (2-3 inches)
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J 33791 Bushing Remover and Installer Set
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J 33792 Side Bearing Adjuster Socket
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J 33837 Pinion Bearing Cup Remover and Installer
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J 36611 Output Shaft Bearing Remover
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J 42213 Side Bearing Adjuster Socket
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J 8092 Driver Handle
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J 8614-01 Pinion Flange Holder[/align]The diff can not be done on the vehicle, it has to be removed, and it is a big job
I'll try to get more info to you when I'm back to a computer....possibly a full day.

 

Thanks for the replies. I am going to pull it off myself no matter which way I go so I was just wondering about the difficulty level of repairing it once I got it off. I've managed to come up with the GM service info on it this morning so I think I'm going to go ahead and take a stab at it. Looks like a lot of tooling but I think I can come up with most of it. I'm not under time pressure now so I think I'd like to learn how to do this as it's the last thing I haven't really done. I've got about every episode of trucks on Tivo or DVD anyway so Ill have to go back and watch it. I just paid big bucksto have a shop put a used one on my Silverado and it went out after two weeks. I was kicking myself for not giving it a try but I thought I would save some time. Since I had to take it back I really didn't save any. Now I guess I've got my chance LOL. Thanks a lot and stay tuned.....

 

Take plenty of pics and post them up.