Transmission humming noise between 40-50 mph

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Modoyadney

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New wheel bearings arrived yetserday, I took everything apart today.
Unfortunately the wheel bearings seem to be in a too good shape to cause this noise.
So I just ordered the diff rebuild kit which includes all four bearings, new crush sleeve, new pinion nut and a new seal.



I really hope this will fix this once and for all.
 
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Modoyadney

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One the the races in the dif looked like that.
Could this be the source of the problem?!
The new bearings will go in next week.
 

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Modoyadney

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Actually the bearing didn't even look that bad.
The bad race is from the carrier bearing. The two on the pinion look like they are alright.
Yet I will still replace all of them, of course.

I couldn't see the surface of the races before disassembly, so there was no way to tell just by visual inspection.
 

rockola1971

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I had the same symptoms on my 99 Sierra Z71. It was the rear axle bearings. Pitted just like yours. Had the noise for close to 2yrs before I fixed it. Im lazy like that.
 

exp500

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With Glitter in the Rear end oil consider changing Wheel Bearings also while it's easy.
 
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Modoyadney

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With Glitter in the Rear end oil consider changing Wheel Bearings also while it's easy.
I put new wheel bearings in already. The plan was to assemble everything this weekend. Unfortunately the pinion seal that came with the rebuild kit didn't fit... :mad:
The old bearings had to be grinded and hammered off the pinion and diff carrier. The new ones came on easy with a regular small shop press.

Everything's ready for installation, I'm just waiting for the seal.
 
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Modoyadney

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Everything is put together again. The loud noise is gone, however the diff still makes a little noise on coast sometimes.
I can live with the way it is now. If it should be like in a new car, I think you really have to replace everything and need all the fancy measurement tools.

I know from now on, that all the bearings and races are replaced and I won't have to worry about the diff again anytime soon (at least I hope so :Big Laugh:).
 

Eman85

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That race looked bad. Did you replace the pinion bearings? How did you set the preload and crush the collar?
 
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Modoyadney

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That race looked bad. Did you replace the pinion bearings? How did you set the preload and crush the collar?
Yeah, I replaced all bearings and races in the axle. I reused the old pinion shim. Since I didn't have the chance to buy a cheap torque wrench with a scale in the range needed here, I used a rod, measured the length of it and used the yoke bolt holes to attach it. Then I calculated the force needed to rotate it with the given length and used a spring scale to measure it.

Probably the pinion depth is not 100% right which causes the soft noise on coast. The gear pattern looks like the pinion is just a very small bit too deep. But not too much to worry about an extreme amount of wear in my opinion.
 

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