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Discussion Starter #1 (Edited)
I let rearend oil change go for about 50K miles and I'm wondering if thats the reason that I'm experiencing noise now. A couple months after the noisy had started, I pulled the cover and drained the oil. While the cover was off, I pulled the axle shafts to check the bearings. They seemed to be OK I also removed the carrier bearing caps and the bearings appear to have good preload. I took a mesh pattern and it was near perfect. Backlash was .005-.006" I removed the drive shaft and turned the diff by hand and everything felt smooth. There was some fine metal particles on the cover magnet but far from excessive. I can't figure out why the rearend whines. And it's worsening. It's not the tires. I tried changing pressures and recently rotated them. No difference. I've done 11 ring and pinion installations in Jeep AMC 20, Dana 30, 35 and 44 axles as well as two Ford 8.8's with 100 % success, so it's not like I'm unfamilar with rearends, however these were all installations and I really haven't done too much trouble shooting. So I'm thinking that maybe my truck needs new carrier and pinion bearings. Although I spun the diff and everything felt smooth, that was without load. Might make a difference? The mesh pattern was great so I can't imagine there's anything wrong with the gears. I'm open to suggestions. thanks in advance, Bob

EDIT: Odometer mileage is 186K
 

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I often see pitting on the inner bearing races. The outer will look ok, but if you push on the outer race when you rotate it you will feel some roughness. Look closely at the rollers for tell tale signs also. Also, a good pattern does not mean that the surfaces don't have some rotational scoring. Overheating a gear can cause the faces to lose their hardness and begin to shed material unevenly and cause noise. Is the noise constant, under load, or on coast?
 

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Discussion Starter #3
I often see pitting on the inner bearing races. The outer will look ok, but if you push on the outer race when you rotate it you will feel some roughness. Look closely at the rollers for tell tale signs also. Also, a good pattern does not mean that the surfaces don't have some rotational scoring. Overheating a gear can cause the faces to lose their hardness and begin to shed material unevenly and cause noise. Is the noise constant, under load, or on coast?
Thanks for your reply. I hate to think about it but perhaps the remedy is a complete rearend overhaul including ring and pinion replacement?
 

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Usually not. I would disassemble it and inspect it all carefully. Just mark the carrier caps and shims. Most of the time it will go right back together without need for adjust
 

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Discussion Starter #5
I took the truck for a drive and I noticed that the sound goes away or is less noticeable when I apply the brakes. Couldit be axle bearings? Also,I've noticed that it really doesn't change much whether under drive or coast conditions.
 

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I took the truck for a drive and I noticed that the sound goes away or is less noticeable when I apply the brakes. Couldit be axle bearings? Also,I've noticed that it really doesn't change much whether under drive or coast conditions.
Yes it could very well be axle bearings, but you said you looked at them. You would check the axle where the bearing rides for pits and wear. Could still be carrier bearings. Usually bearing noises will change when you load and unload them. It could also be a transmission bearing noise. Those are often speed related. You could put the rear up on jack stands, let it run in gear, and listen for where you hear it. I use a stethoscope, but an extension or long screwdriver pressed to your ear also works in a pinch. Just be careful.
 

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Discussion Starter #7
Yes, I did look at the axle bearings and axle shafts where the bearings ride but to tell you the truth I'm kinda at wits end now and the noise characteristics have changed. Now the noise diminishes noticeably when the brake is applied even lightly and the service manual trouble shooting guide indicates that a noisy axle bearing will respond to brake application.
 

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Put the truck on axle stands, put truck in first gear, let it freewheel for awhile. See if the diff nose is hot or very warm to the touch. Also use a long hollow pipe, 1/2" copper pipe works well... touch it to the diff nose and put your ear to the other end. The 7.5/7.6's are pretty notorious for pinion bearing failure, and pinion bearings on their way out tend to make a lot of rear end noise that is often mistaken as brake or axle related. The mesh pattern and gear teeth are a less common source. Although the 7.5/7.6's are weak under flex and experience ring climb under substantial torque/high hp, that usually isn't an issue in stock trucks.

Odds are you need a new pinion bearing + new crush sleeve. I hate crush sleeves, if you over crush a new sleeve you get the same premature bearing wear and noise issues...

The other thing I'd be inclined to check if you have a two piece driveshaft is to have it rebalanced and check the universals. The 3R44 universals aren't the beefiest thing in the world and they tend to wear out. I had to replace a few on my truck over the years before I did my LS swap. The diff yoke universals tend to wear out more because the stock S10 has more driveshaft misalignment than it really should have, which is why JTR makes and sells a driveshaft alignment kit thats been quite popular over the years, and I used myself.

Anyway TLDR check pinion, check driveshaft, one of the two is my educated guess.
 

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I can fell your pain when you here a noise and can't put your finger on it. Had that same problem w/ my Silverado for over a year that just seemed to be getting worse. As Briglicon suggested listening with a stethoscope on stands it sounded like the rear. I pulled it down and actually happy to find pitted bearings as he suggested earlier (not that this is your problem)









 

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Discussion Starter #11
Man, my truck is still making that noise. It hasn't gotten louder but it's starting to occur at a lower RPM now. Could it be the drive haft enter bearing? I hurt my shoulder so it probably won't be a few days before I can get under there.
 

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Could be. Those extended cab are notorious for having issues with that bearing.
 
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