75w90 or 75w140?

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Yeah, I know there are others who have commented on this, but let's put forward the scenario and see what people think.

2002 1500 Suburban, 5.3L, standard G80 roller locker. Used mostly/almost always for hauling or towing; boats historically, last four-five years including a cargo/RV trailer up to 7k gross (w/weight distribution.)

It appears the diff has eaten the bearings. Light dusting of silver on the magnet, oil looked ok when drained, no "pieces" of anything in the oil, ring gear looks fine, of what I can see without removing the axles and chunk the pinion looks ok (can't tell for sure as the the chunk isn't out yet) but its got a nice growl starting at ~20mph (zero noise below that) which is not load-dependent; it makes noise at higher speeds in gear or out, accelerating or decelerating, and while there's a BIT of a difference under hard acceleration its not a lot. With the rear end on stands it you can clearly hear it once put in "D" and the "speed" gets to 20mph or above -- its definitely in the differential and not one of the wheel/axle bearings. Replacing the gear oil did nothing, so here we are and I'm going to be tearing it down, replacing all the bearings plus whatever else I don't like when it comes apart. It made the back half of a 1,000 mile trip with the noise and did not get progressively worse.

Truck has roughly 100k miles on it; gear oil has been changed on roughly 30k intervals, and always full-synthetic and "as recommended", meaning synthetic 75w90.

It LOOKS like I caught this before the damage wound up destroying the gearset but I don't feel like doing this job again. Once I have the chunk and pinion out I'll see if anything looks trashed there, but at first blush I suspect its bearings-only in terms of what's dead and needs to be replaced.

So...... do I run the 75w90 or do I go to 75w140, assuming both options are full-synthetic? The latter should flow the same at lower temperatures but since its full-synthetic there should not be a problem with VIs shearing over time, which can be with wider-viscosity spreads on dino-based oils. The truck is going to continue to be mostly used for towing and given the stupidity in new and more-recent used truck prices, never mind that it runs great and while the paint is somewhat hosed I might actually invest in having it painted.

Thoughts?

I will be interested to see what you find when you get it apart. Perhaps the issue is at the axle bearings rather than the pinion. I have a ‘97 C2500 Suburban that towed heavy most of its life, It required new axles and bearings early in its life, and has needed a few axle bearings & seals and since then. Two years ago the pinion seal was replaced and the bearings looked good. This is all with AC Delco 80w-90, currently at 175K miles.

Personally I think your issue is due to the long term durability of the axle design and towing at capacity, not your choice of gear oil.

I would refill with a synthetic 75w-90 like Chevron Syn-Gear or Mobil Delvac 1. Both are relatively easy to find and contain no friction modifiers.
 

tickerguy

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This is pretty-clearly the cause of the noise..... :cool:

Interestingly enough the rollers are in perfectly good shape as is the other (front) bearing on the pinion; the carrier bearings also appear to be perfectly fine. Yes, they're all getting replaced; I have it apart and I'd be an idiot not to do so..... Everything else looks ok, so obviously I caught it before the shrapnel level got out of control.

Lash was in-spec before I took it apart (.007-.008; spec is 6-10) so provided the bearings are the same size (ha; maybe not) when it goes back together the factory shims MIGHT put everything in the same place. We'll see.
 

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This is pretty-clearly the cause of the noise..... :cool:

Interestingly enough the rollers are in perfectly good shape as is the other (front) bearing on the pinion; the carrier bearings also appear to be perfectly fine. Yes, they're all getting replaced; I have it apart and I'd be an idiot not to do so..... Everything else looks ok, so obviously I caught it before the shrapnel level got out of control.

Lash was in-spec before I took it apart (.007-.008; spec is 6-10) so provided the bearings are the same size (ha; maybe not) when it goes back together the factory shims MIGHT put everything in the same place. We'll see.
Wow that spalling is crazy! It’s been awhile since my brain was tuned into spalling causes, but on camshafts it’s when there is generally a hammering action (lifter bounce) between the roller and lobe; in this instance I’d say when the pinion was snugged in tight there was a ton of pressure & maybe even some back & forth (thousandths, of course)- maybe the end play was too high allowing the pinion race to move too deep into the bearing & overloading it? I could always be off in my thinking, though… Thanks for the pics!
 
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This is pretty-clearly the cause of the noise..... :cool:

Interestingly enough the rollers are in perfectly good shape as is the other (front) bearing on the pinion; the carrier bearings also appear to be perfectly fine. Yes, they're all getting replaced; I have it apart and I'd be an idiot not to do so..... Everything else looks ok, so obviously I caught it before the shrapnel level got out of control.

Lash was in-spec before I took it apart (.007-.008; spec is 6-10) so provided the bearings are the same size (ha; maybe not) when it goes back together the factory shims MIGHT put everything in the same place. We'll see.
The morons in Kemah, TX who set up the rear axle on my Jeep set it with WAY too much carrier preload and in less than 15K miles my pinion races looked like a roller coaster and was starting to spall.
 

tickerguy

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This is quite interesting in that everything in there is OE; the only thing that has been changed since the truck was new is the pinion seal and, when I got the carrier out I checked the preload on it -- bang on, as was the lash between pinion and ring before I took the chunk out. Engagement and wear pattern is right up the middle; no evidence an assembly problem at the factory.

While there is a very, very small amount of scoring on the rollers on the big pinion bearing its barely visible and won't snag a fingernail. No discoloration or other evidence of heat, and the front (smaller) pinion bearing and its race are perfectly serviceable, as are the carrier bearings and races.

I'm changing all four bearings, obviously, plus axle seals. Axle bearings are ok too (those aren't very hard to change if I have to at some point in the future and if you do those since the axle is the other running surface there's a clean argument you should change the axles too.)

This one's a puzzler as to WHY.

Here's a couple more pictures; the race and bearing with both out....
IMG_20220921_143405_01.jpg
IMG_20220921_144326_01.jpg
 
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That's odd. The only thing I can think of is excessive foam lead to cavitation. I'm not really sure though. I've yet to pull anything out of my 2002, but it hasn't given me a reason to. (yet... *knock on wood*)

My Camaro drag car still has the weak 7.5" 10 bolt with stock axles and diff and 4.10 gear. I have it installed at zero preload. Just enough to take up the slack. It takes a lot of abuse, all things considered. No noise from it.
 
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This is quite interesting in that everything in there is OE; the only thing that has been changed since the truck was new is the pinion seal and, when I got the carrier out I checked the preload on it -- bang on, as was the lash between pinion and ring before I took the chunk out. Engagement and wear pattern is right up the middle; no evidence an assembly problem at the factory.

While there is a very, very small amount of scoring on the rollers on the big pinion bearing its barely visible and won't snag a fingernail. No discoloration or other evidence of heat, and the front (smaller) pinion bearing and its race are perfectly serviceable, as are the carrier bearings and races.

I'm changing all four bearings, obviously, plus axle seals. Axle bearings are ok too (those aren't very hard to change if I have to at some point in the future and if you do those since the axle is the other running surface there's a clean argument you should change the axles too.)

This one's a puzzler as to WHY.

Here's a couple more pictures; the race and bearing with both out....
Maybe it is a defective race or substandard materials? You would expect to see the scoring reciprocated onto the bearing rollers and while there is a little, it is nothing compared to the race. Then again, there are multiple rollers and only one race so the load is a bit concentrated.
 

tickerguy

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Possible. The race and roller both have Timken stamps and part numbers on them, but could GM have gotten counterfeit ones 20 years ago? Yes. Is that common today? You bet it is..... My money given the lack of any OTHER evidence of damage is a defective part, whether just bad from the factory or GM got a run of them that weren't really made by Timken despite being stamped that way.....
 
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I used AMSOIL's Severe Gear 75w-90 in my 2002 Silverado 1500 from the time I got it home until I sold it at 208k miles. I did a drain at 75k miles and then again at 190k miles and had a UOA. I'm trying to find it but not sure if I lost it when my computer dumped. But it came back great. I towed frequently a 10'x20' box trailer at 4k lbs. I didn't see a need to go heavier, the 75w-90 served me well. But then to me AMSOIL's gear oil is hard to beat.
 

tickerguy

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Well, well, well.... let's see if you can tell me why the failure happened. Three photos; identify them and you'll understand.

Oh yeah, I ain't happy, not that I can do anything about it 20 years later.
real.jpg
side-2.jpg
side-1.jpg
 
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wwillson

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This is quite interesting in that everything in there is OE; the only thing that has been changed since the truck was new is the pinion seal and, when I got the carrier out I checked the preload on it -- bang on, as was the lash between pinion and ring before I took the chunk out. Engagement and wear pattern is right up the middle; no evidence an assembly problem at the factory.

While there is a very, very small amount of scoring on the rollers on the big pinion bearing its barely visible and won't snag a fingernail. No discoloration or other evidence of heat, and the front (smaller) pinion bearing and its race are perfectly serviceable, as are the carrier bearings and races.

I'm changing all four bearings, obviously, plus axle seals. Axle bearings are ok too (those aren't very hard to change if I have to at some point in the future and if you do those since the axle is the other running surface there's a clean argument you should change the axles too.)

This one's a puzzler as to WHY.

Here's a couple more pictures; the race and bearing with both out....
View attachment 117892 View attachment 117893
I'll bet @Kestas can give a professional opinion what causes a race to fail like this.
 

tickerguy

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Here's a couple more images that make one point very clear -- whatever that bearing is, it's not Timken but the race is. Timken marks all their parts and there are no markings on the rear bearing -- but there are on the race. This was installed at the factory; I'm the original owner of the truck and the differential has never been apart until now.

The other bearings -- front pinion and both ends of the chunk -- are in perfectly good condition, the preload was in-spec on the pinion before I removed it and the lash was in-spec before the chunk came out.

Its getting all four bearings replaced and put back together; I can't find anything else wrong with it and this is clearly the failure itself, which certainly does not, at this point, appear to have had anything to do with running synthetic 75w90.
janky-2.jpg
janky-1.jpg
 
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Here's a couple more images that make one point very clear -- whatever that bearing is, it's not Timken but the race is. Timken marks all their parts and there are no markings on the rear bearing -- but there are on the race. This was installed at the factory; I'm the original owner of the truck and the differential has never been apart until now.

The other bearings -- front pinion and both ends of the chunk -- are in perfectly good condition, the preload was in-spec on the pinion before I removed it and the lash was in-spec before the chunk came out.

Its getting all four bearings replaced and put back together; I can't find anything else wrong with it and this is clearly the failure itself, which certainly does not, at this point, appear to have had anything to do with running synthetic 75w90.
It could have been a supply chain issue, where they had to deviate back then and it could have been substandard parts. When you get it back together I would switch to 75W-140 anyway given the towing that you do.
 
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GM is known to mix bearings brands like I stated in a earlier post, GM used to almost exclusively use Hyatt Bearings as it was a subsidiary of GM. Then sometime in the mid-late 80's....GM started outsourcing & it's been chaotic ever since.
 

tickerguy

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But between a bearing and its mating race?

Anyway, its going back together with Koyo which I can source easily and are known to be of good quality. It bites having to spend more in tools you don't have to not fight a specific job than the parts cost, which is the case here. Ah well, now I have 'em.
 

Kestas

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With tapers it's okay to mix cups and cones. This style bearing is unique in that regard. Otherwise you just don't mix components with bearings and they are considered a matched set.

From what I see, the race has advanced surface initiated spalling concentrated in the load zone. I don't see any mirror-like character to the raceway, so it does not look like lube failure. I don't see any roller spaced damaged to suggest an impact event or stationary brinelling. It looks like simple overload. I do see some frosting on the raceway, which would merit closer examination.

The spall pattern does show that loading was properly centered on the raceway with no edge loading.

It's very rare to find hardness or metallurgy substandard with a bearing.

It's also an impossibility to find cavitation on the raceway for this application.
 
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Pinion bearings are usually the first to go. 20 years is good life. We would all like them to live forever but that’s not the way things work

Any history of pinion seal replaced ? Those era diffs the seals leaked and was common replacement and many times were over tightened pinion nut. Or too loose pinion nut a factor as well but less common.

How clean is the housing like was lube able to flow through the pinion trough area back there easily ?

Fluid could have broken down depending on load and duration.

Would replace parts set up to your numbers you like and fill with amsoil
 

tickerguy

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I replaced the pinion seal myself several years previous and was extremely careful with the pinion nut (marking the exact position it was in before I removed it) as I'm very aware of the preload problem and that there's no accurate way to check it without removing the chunk. On inspection this time before I pulled the pinion I took the chunk out first and checked the preload -- it was in-spec, right up the middle, so that validates that I got it right when replacing the seal.

The housing is very clean; no issues with the lubrication paths and while I also had replaced the cover previously I didn't try to get cute; it was a factory-style "rounded" rear cover as I'm well-aware of the problems with the flat-back ones interfering with the ring gear properly slinging oil forward. Oil only had about 20k miles on it as well.

What surprised me was that it was only the race that was damaged; since I had to cut the cage off the large bearing to get it off the pinion I have a good look at the running surface of the bearing itself; there's no evidence of lubrication failure either on that surface or the rollers. Thus my curiosity.

I don't expect "forever" sort of life but 100,000 miles is well below expectations particularly given that I'm the maintenance source on this thing and yes, the fluid has been changed on reasonable (~30k or so) intervals since it was new and there's never been any evidence of water intrusion or similar in the unit.
 

4WD

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GM is known to mix bearings brands like I stated in a earlier post, GM used to almost exclusively use Hyatt Bearings as it was a subsidiary of GM. Then sometime in the mid-late 80's....GM started outsourcing & it's been chaotic ever since.
Plus AAM in the mid 90's to date ...
 

tickerguy

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So final update on this. Diff is back together, nice and quiet. All (four) new bearings, surprisingly replacing only those and keeping the factory shims "as originally installed" resulted in lash being in-spec exactly as it was before the chunk was removed. Now running 75w140 synthetic.

I'm not particularly happy with the handful of tools I had to buy and didn't have but if I ever have to do one of these again I've got 'em now; if anything in the roller locker or ring and pinion eventually wear out I'll stick a Posi chunk in there instead along with a new ring and pinion, but from what I saw that's probably a long way down the road.

Parts total that actually went into the diff = 4 bearings+races (Spicer kit; Koyo and Iljin) and both axle seals, plus obviously the crush sleeve, pinion seal and nut.
 
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