Transmission humming noise between 40-50 mph

[Modoyadney]

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.

 

[Modoyadney]

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.

 

[exp500]

That would probably be your noise. The bearing had to be pretty bad too. You couln't tell by visual inspection before disassembly?

 

[Modoyadney]

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]

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]

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

 

[Modoyadney]

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...
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.

 

[Modoyadney]

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 ).

 

[Eman85]

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

 

[Modoyadney]

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.