What wrecked these differential carrier bearings?

Since the beginning of my ownership (end of 2011) of this truck (1996 2wd Chevy 5.7) the rear axle/differential has made some abnormal sounds. Noises could be best described as rumbling, whirring when speeds are greater than 20 MPH. I changed the gear oil back when I took ownership with no impact to noise. The last 3,000 miles the noises increased. It sounded like rocks in the rear axle area.

Last weekend I visited my local Pull-a-Part and found a lower miles entire axle assembly from similar truck with a better gear ratio 3.73 (versus the old 3.08). Cost was only $100 and two hours of my time to remove it. I performed the swap to my truck and all noises are gone plus much improved low end acceleration!

Today I disassembled the old axle to see what was going on. During carrier removal I found no carrier shims, this seemed weird to myself. Once I got the carrier out I found one damaged carrier bearing and the other seems in decent shape. The bearing on the pinion closest to the gear was also damaged. Ring and pinion gears are in great shape. The bearings are marked Timken wonder if these are factory?

Below are photos of the damage what causes this type of bearing damage?

Carrier Bearing Side A

Carrier Bearing Side A photo two

Carrier Bearing Side B

Pinion Bearing

Thanks!

That's about normal for a 1/2-ton 10-bolt at around 100k, give or take a dozen.

Near as we could ever figure, GM erred to the side of soft and tough for the gears, instead of hard yet brittle, so the gears wear. Eventually they wear through the hardening and you get 90-weight glitter which eats the bearings. I'd bet that your gears have no discernible pattern to them.

I've done quite a few overhauls. Randy's Ring & Pinion will sell you Yukon gears that are OEM fit, meaning you use the shims that came out and everything will be right. Haven't had to fiddle around with shims once after we started using them as a supplier. The biggest concern is getting all of the glitter out of the housing, I like to flow kerosene through while swabbing the tubes out with a rag stuck on a long piece of welding rod chucked into a drill. I bend the end like a big paperclip to hold the rag. Then more kerosene and brushes in the housing, then final clean with brake cleaner.

Funny thing is, the stuff from Randy's lasts longer than OEM.

I agree. OEM stuff is good, but not perfect. The carrier A looks pretty consistent with a tight backlash. OEM stuff is supplied by the lowest bidder and changes every few months. Factory assembly tries to take into consideration the things like wear and time. Pinion depth is set by computer and the pinion is assembled with the proper shim. The carrier is installed on the tight side of backlash knowing that the gear wear will eventually make backlash correct. Change suppliers and things can change.

The fact that your ring-side carrier is worse than the open side indicates tight backlash causing the needles to "pare" or flake off their hardened coating. Since the rear pinion bearing carries the majority of that side-load, it took the punishment too.

Looks all around like backlash was too close for comfort... or simply faulty bearings.

Dodge also did this mistake a lot in their 9.75" truck axles. Our shop did a ton of Dodge axles with bearings that looked exactly like yours.

I have nothing to add except that just looking at those photos and I started to smell diff oil. That stuff is worse than snot. It seems to get everywhere and that distinctive smell.. ... Makes me shiver thinking about it.

I swab axle tubes w/ this wired inside the end of conduit, and kerosene like knurled said.

No shims between the side bearing outer races and the diff housing? If none, the carrier should have been bouncing around like nuts.

Thats a pretty typical bearing failure, although its more often the front pinion bearing that goes south first. I'm never sure whether it starts from too much preload, or just a bit of hard surface comes off, then continues to rattle everything to pieces.

I disagree about the source of the problem being the gears. I have replaced dozens of sets of bearings, and as long as they did not wear to the point that stuff was loose, gears are not required, and would last as long as the old bearings had.

Maybe. By the time the noise was annoying enough that they'd have us pull the cover off for a look, the gears would be junk. Chicken or egg? Once in there for the bearings, the gears are only a little bit more. It's hard to believe that the bearings would fail like that after such a long period of time. Typically, excessive preload failures happen rather quickly.

The factory shims don't look like shims, they're roughly 3/16" thick rounds of iron.

Knurled wrote: Maybe. By the time the noise was annoying enough that they'd have us pull the cover off for a look, the gears would be junk. Chicken or egg? Once in there for the bearings, the gears are only a little bit more. It's hard to believe that the bearings would fail like that after such a long period of time. Typically, excessive preload failures happen rather quickly. The factory shims don't look like shims, they're roughly 3/16" thick rounds of iron.

plus eleventy billion. I've done enough to know that how the gears "look" really doesn't say anything. Of course, I'm speaking from the standpoint of a shop where we have to warranty our work. The frustrating thing is, if you rebuild the whole thing and get it perfect, the gears might whine like a mule. Then you're looking at another rebuild, and I don't like re-using bearings once they've been pressed on and off. Its hard to get them off without damage, nicks, or bending.

Instead of risking another $150 in bearings, lube, gaskets and double labor, might as well pony up the $200 and just get new R&P and do it right.

Also agree on the factory shims. Factory parts bins have a wide variety of shim thickness so they limit the "stacking" necessary to get the right setup. My GM 8.5" that I just did had one shim on each side. I was able to re-assemble using one additional paper-thin shim on the drive side and nothing else. Stacking makes trouble.