Tire hum or???

[RogueJeepr]

Is that paint ?
It's hard to tell with that, but it looks like it's the outside of the teeth. You'll want it more in the centered.
I know enough to be dangerous but maybe I-lean will chime in from more of a professional view.

My boss had some horrible tire hum from the rear of his Chevy which are notorious for axles going out. It was the tires.
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[Gravy]

You need to stuff a rag or something between the ring gear and the housing so you can get more drag on the ring. (You want a lot, like you can barely turn it).
(the pattern now is inconsistent from one tooth to the next, You'll expect to see a similar pattern on 3 or more teeth).

AND

take the photo further out.

We need to see a photo of the face of the gear tooth (not the end of the tooth) on both sides (drive and coast).

(your photos are crazy it's giving me a headache trying to look at them from that angle).

You can't tell lash (backlash really) from a pattern. You need to put a dial indicator on the ring gear and rock it back and forth. ( I have one if you want to borrow it).

 

[Kevin B.]

I think I got that backwards above, the convex side should be the drive side side. That's the side with the pattern falling all the way off the heel.

I'm on my phone, so take that into consideration. Looks horrible to me, I'll bet you have bearing issues

Looks horrible to me too.

Is that paint ?

It's hard to tell with that, but it looks like it's the outside of the teeth. You'll want it more in the centered.
I know enough to be dangerous but maybe I-lean will chime in from more of a professional view.

This is that special gear marking compound you get at the Dollar Store right next to the eyeliner.

Carl's camping, I'm not going to bug him any more than I have.

You need to stuff a rag or something between the ring gear and the housing so you can get more drag on the ring. (You want a lot, like you can barely turn it).
(the pattern now is inconsistent from one tooth to the next, You'll expect to see a similar pattern on 3 or more teeth).

AND

take the photo further out.

We need to see a photo of the face of the gear tooth (not the end of the tooth) on both sides (drive and coast).

(your photos are crazy it's giving me a headache trying to look at them from that angle).

You can't tell lash (backlash really) from a pattern. You need to put a dial indicator on the ring gear and rock it back and forth. ( I have one if you want to borrow it).

I'll try and get some better photos.

 

[Kevin B.]

Any better?

Convex side

Convex side closeup

Concave side

Concave closeup

If convex is drive and concave is coast, I feel like I've found the source of my noise.

 

[TRD270]

Time for one tons and 40's

 

[dutchman]

Time for one tons and 40's

This or long travel with shocks up through the bed.


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[Gravy]

Excellent pattern photos BTW.

Low pinion rear: so drive is on the convex and coast is on the concave.

Coast side is good. Drive is out toward the heel but it's not the worst. The biggest contact patch is still far enough in that it's not worrisome (like you shouldn't be worried to shear teeth).
My money is on carrier bearings going out. It can lead to excessive backlash (which could explain the shift in pattern from drive to coast. If the ring is pushing to the left away from the pinion on the gas). I wish I could articulate how much backlash is too much based on the amount of "clunk," but it's really a feel thing without a dial indicator. Come borrow mine if you want to know for sure.

That 9.75 semifloat Sterling is a tough diff. I'll bet it was run low at some point in its life for that kinda wear.

 

[Kevin B.]

Excellent pattern photos BTW.

Low pinion rear: so drive is on the convex and coast is on the concave.

Coast side is good. Drive is out toward the heel but it's not the worst. The biggest contact patch is still far enough in that it's not worrisome (like you shouldn't be worried to shear teeth).
My money is on carrier bearings going out. It can lead to excessive backlash (which could explain the shift in pattern from drive to coast. If the ring is pushing to the left away from the pinion on the gas). I wish I could articulate how much backlash is too much based on the amount of "clunk," but it's really a feel thing without a dial indicator. Come borrow mine if you want to know for sure.

That 9.75 semifloat Sterling is a tough diff. I'll bet it was run low at some point in its life for that kinda wear.

This truck was rode hard and put away wet in it's past life, it wouldn't surprise me if I found out the diff had been overheated. I didn't find any metal slivers or excessive sparkly goo and I don't see any discoloration on the ring and pinion, think they're ok to reuse?

Thanks for the offer to borrow the dial indicator, I think I might just buy one though. I've been back and forth about tackling this myself or taking it to somebody, and I think I'm leaning towards doing it myself. It's about time I learned how to set up gears anyway, so we might change this from an "ID this noise" thread to a "watch Kevin f*** up a diff" thread.

 

[Gravy]

You don't need to setup gears. Just new bearings. Use the same brand and they "should" have the same width.

 

[Kevin B.]

You don't need to setup gears.

Just pop the carrier bearings off, replace with identical bearings (or shim to make them match) and put it back in the truck? That sounds suspiciously easy.

You really think it's just the carrier bearings though? If one or both of them are bad, the pinion bearings can't be far behind I'd think. I have terrible luck when I try to do half a job and leave the rest for later, because later generally comes a week before a big trip. Even if I knew for a fact it was just carrier bearings, I think I'd still lean strongly towards rebuilding the entire thing on general principles.

 

[I Lean]

Replace them all.

 

[RogueJeepr]

My neighbor is getting ready to sell his truck if your interested ?

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[Kevin B.]

I've got a billion excuses for diving into this until now, but we all know what excuses are like. Posting to get a reality check from some of you that have been there and done that:

Baked on schmoo (I changed this fluid shortly after buying the truck, it ain't my schmoo...).

Shims are cracked and have funny wear patterns - circular gouges, roughly half a millimeter deep in some spots, and they aren't centered.

Has this diff been abused? I have a full Yukon rebuild kit (thanks AllJeep!), but now I'm worried about the ring and pinion.

 

[RogueJeepr]

I wonder if a bearing had spun ?
An old axle I had, the pinion bearing had spun and a new oversized bearing was put in but didn't fit as tight as he wanted so a glue of some sort kept it from spinning again. It was short lived.

Dont need big tires to have fun.

 

[Kevin B.]

I wonder if a bearing had spun ?

Both of them, looks like. The pinion bearing wasn't seated right either, and the lash was a hair over 20 thousands. Still don't know if the diff is what was making the noise I'm chasing, but either way it was definitely f*cky and I'll feel better having it rebuilt.

Carl came over earlier and did heroes work trying to get it put back together, but we couldn't get the crush washer to compress. Gonna take another swing at it tomorrow.

 

[gijohn40]

The day Carl decides to move out of state is going to be a bad day for alot of us!!! He is the man!

 

[Kevin B.]

I can state with authority that the driveshaft was not the source of my noise.

Ended up needing to put the crush washer in my press to squish it down to size, but it worked. Everything else went together fairly smooth and the big bitch is back on the road, with no hum and no rattle. Big ups to Carl for the assist.

I'm going to get a decent compressor and impact gun before I try this job again though.

 

[RogueJeepr]

Cool. Just in time for camping season.

Dont need big tires to have fun.