Rear end noise, can't figure it out!

[AirSpeed]

I have an 87 K5 I don't drive often. I drove it today and heard a noise coming from the back of the blazer, I thought it was the parking brake rubbing so I took off both dorms, cleaned the brakes and backed off the parking brake adjuster, noise still there. Next I jacked the rear end and spun the tires manually and can clearly hear a soft dull thud sound that increases with speed. I had a friend push the brakes to see if the sound would change, it didn't. I checked the u joints and they are good. I feel no vibrations, only sound. Any ideas what I should look for next? Any help diagnosing this would be greatly appreciated!
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[Weasel Diesel]

remove the rear wheels & brake drums. This will eliminate the brakes all together. See if noise still exists. If it doesnt, then the problem is in the brakes, or drums rubbing backplates. If the noise is still there, then remove the rear driveshaft and see if noise is still there. If it is not, double check the driveshaft and or transfer case. If it is still there then you will need to check diff internals such as axle bearings and ect.

[AirSpeed]

Originally Posted by Weasel Diesel

remove the rear wheels & brake drums. This will eliminate the brakes all together. See if noise still exists. If it doesnt, then the problem is in the brakes, or drums rubbing backplates. If the noise is still there, then remove the rear driveshaft and see if noise is still there. If it is not, double check the driveshaft and or transfer case. If it is still there then you will need to check diff internals such as axle bearings and ect.

Thanks! I will try as you suggest, I'm hoping at worse its only a wheel bearing. Odly I've never had to change a rear wheel bearing, lots of fronts but never a rear. Is it as simple as removing the bolts at the backing plate, pulling the diff cover and removing a clip on the axle? Are the bearings pressed on? Thanks again! Aaron.
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[INSIDIOUS '86]

If you have a gov lock diff. Stop driving it immediately. It will grenade and blow and lock up your rear wheels.

Pull your diff cover and check the insides
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[AirSpeed]

Originally Posted by INSIDIOUS '86

If you have a gov lock diff. Stop driving it immediately. It will grenade and blow and lock up your rear wheels.

Pull your diff cover and check the insides
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What's a gov lock? How do I identify one? Thanks!
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[kelsfine69]

Originally Posted by AirSpeed

Thanks! I will try as you suggest, I'm hoping at worse its only a wheel bearing. Odly I've never had to change a rear wheel bearing, lots of fronts but never a rear. Is it as simple as removing the bolts at the backing plate, pulling the diff cover and removing a clip on the axle? Are the bearings pressed on? Thanks again! Aaron.
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Yes pulling the center diff pin out then the axle c-clips...If it all looks good when you pull the cover off then go ahead and pull the axles. This would be the time to put new bearings and seals in. You will need a bearing removal tool on a slide hammer cause they are IN there.

[AirSpeed]

I took the Cover off the differential and found three teeth missing from the pinion gear, the are clean breaks and luckily didn't fly into the diff! The rest of the gears look perfect, I can't find even a scratch on them. So I'm thinking I simply need to replace the pinion, assuming that's the correct name, it's the input gear attached to the yoke.
Where do I find a replacement? Is this a part available at a parts store or should I look at the junk yard? Any ideas what they cost? Will I need to do any kind of shimming? Any details will be greatly appreciated!
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[Keith Seymore]

Originally Posted by AirSpeed

I took the Cover off the differential and found three teeth missing from the pinion gear,

That would do it....



You'll need to replace the ring and pinion as a set (you can't replace just the pinion gear and not the ring gear too).

It will need to be "set up"; it's not rocket science but if you don't know what you are doing it would be best to have someone else do it, or talk you through it.

K

[kelsfine69]

Now would be the time to Swap in a Auburn posi Cause the Gov-lock could crater and take your new ring gear with it. Yes its more money but in the long run it would be worth it. If you plan on keeping the truck for awhile I would definitely. FYI I had 2 teeth missing on mine and they took the spider gears out and made a mess.

[AirSpeed]

Originally Posted by Keith Seymore

That would do it....



You'll need to replace the ring and pinion as a set (you can't replace just the pinion gear and not the ring gear too).

It will need to be "set up"; it's not rocket science but if you don't know what you are doing it would be best to have someone else do it, or talk you through it.

K

I was afraid that would be the case, so Can I buy these new or am I on the way to the junk yard? I just pretty much gave this Blazer away and dont want it to break down on the kid but I also don't want to spend a fortune at the same time. My local NAPA is closed today so I can't check with them. Thanks!
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[AirSpeed]

Originally Posted by kelsfine69

Now would be the time to Swap in a Auburn posi Cause the Gov-lock could crater and take your new ring gear with it. Yes its more money but in the long run it would be worth it. If you plan on keeping the truck for awhile I would definitely. FYI I had 2 teeth missing on mine and they took the spider gears out and made a mess.

I got lucky there! All the chunks stayed on the bottom, glad I didn't hit any bumps and make them fly up into the rest of the gears!
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[Weasel Diesel]

Must be a West Virginia pinion... 3 teeth missing...... I'm glad to hear you found the problem.

[Your41Plague12]

Originally Posted by Weasel Diesel

Must be a West Virginia pinion... 3 teeth missing...... I'm glad to hear you found the problem.

I just lost it. Nice one!

OP, also glad you found the problem.