Rear 3.42 rebuild odd axle bearing wear

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View attachment 462669
Damaged OEM bearings, axle shaft shows identical marks inside where bearings run
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Second photo of damaged OEM bearings
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Third photo is New Timken on Left, damaged OEM bearings showing the back un damaged side on right.


I am rebuilding the rear Differential on my 08 Denali. Main complaint is a rear axle whine while accelerating. I plan to install all new bearings, Pinion, Carrier and Axle along with a rear brake job as part of this repair.

Before tear down I was hoping my noise would be found to be a Pinion Bearing failing. I don't have them out yet but pulled both axles and the axle bearings. Found the Pass side had a seal leaking at the axle bearing.
Pulled both axle bearings and found the same odd marks on the outside of the bearings and in the axle tube, both on the TOP of the housing facing the roof of the car????

I worked for a bearing manufacturer for 30 years, saw lots of bearing failures and normal wear bearings over the years. Have never run across this type bearing damage.

I took a couple pictures of the old bearings showing the wear and the opposite side showing they look perfect. All the rollers show no wear I have found?

The new bearings came in, Timken, still Made in the USA. I was shocked thought for sure they would be China made.

My only guesses would be that someone Welded on this vehicle while these bearings were in the car and the weld grounded through the bearings? If it was from going over a hard bump while driving I would expect differing damage side to side?

I will pull the pinion bearings out for inspection next then the carrier bearings, I have new replacements ready to go.

The last thing I am worried about is the Ring and Pinion gears. I am concerned they may have been damaged due to the leaking axle seal lowing the oil level? Noise on Tip in is normally gear noise not bearing noise? My noise did not change in pitch while turning left or right and goes away when you let off the throttle. I have ordered a new Ring and Pinion set so I will be prepared if that is needed. At this point I am wondering if I should have purchased a complete axle assembly to drop in.

Curous what you guys have seen in the past.

Any chance this was driven with a sagging rear end? Bad rear shocks or compressor? Would that be enough weight over time to cause wear on the top?

Is this an AWD or RWD 2008 Yukon Denali?

Post up pictures of the inside of the tube where the bearings go and the ring and pinion when you pull all that apart. I overhauled one last year.

You can have my old 8.6, it's still sitting on my driveway and works just fine.

Timken and Koyo bearings were used in these and really, there's none better. I have found that buying the kits from AAM, the axle manufacturer, saves quite a bit of money.

AAM is about 10min up the road from me. I’m curious if I can buy a 9.5” and pick it up in person. Save myself on delivery fees.
Even buying one from a scrap yard will cost me $200-400 for delivery.

 

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Follow up #2. This is a 08 6.2L non AFM, non variable cam timing. 6 speed with the 3.42 gears. I did feel the 3.42 are too high at least with my loaded truck on this trip. At 75 it stayed in 6th gear and pulled well, at 65 it kept shifting down on the mild hills. I bet the 3.73 gear ratio would be a better choice with this engine and tranny. With 3.42 gears it is taching about 1800 RPM at 75 mph.

Is yours the 8.6” or have you replaced it with the 9.5”? Mine is the 8.6” with the 3.42, but they have the 9.5” in the 3.42 ring gear as well. I believe the 3.73 is the 14 bolt? Does that sound right?
I should remember this @swathdiver and I were just discussing this last week or two.

Any chance it could be the TC whining or a U-joint going bad? I thought mine was everything else first, but it turned out to be the race for the pinion yoke. Which of course is the first thing installed in the rear diff. Making replacement a super easy and quick job. 15-20 min max

 

[alpha_omega]

is the whine exactly the same as before? Definitely sounds like gear whine from the description.

could be a good excuse for a set of mechanics ears. i got some and found my odd noise was a front wheel bearing, and on the opposite side of the car as I thought the noise was coming from. little prices for the nice wireless ones. but I'm happy I have them for things like this.. maybe it's the front diff? or tranny? transfer case?

What ears are you guys using these days? I have a relic of a stethoscope plus mine from the hospital, but neither would help in this situation. Other than maybe checking my heart rate after seeing the bill for my race replacement.

I’ll be curious to see what condition my axle shafts are in and whether or not I have any damages. I know one of my seals is bad. Probably the side that had a blown out air shock, due to someone not starting the vehicle prior to loading a trailer full of weight. That was an exciting and expensive trip.

 

[exp500]

The axle bearings showed the odd wear or damage posted early in this post. It was on the outside of the bearings not on the rollers. The axles looked perfect. The axle housing showed the identical marks that the bearings showed which had me thinking someone welded on this truck maybe or very heavy load was hauled.

My experience with this is towing a car trailer with 1/2 ton. Empty no problem, loaded limit runs 100 miles or less,no damage. After 200 miles damage accelerates fast. I changed many sets of bearings/axles before 14 bolt swapped in. Long story....

 

[West 1]

Weight on the axle is identical with shocks pumped up or blown so stress on a bearing would be the same. With my 2003 Yukon, same axle set up, I towed hundreds of times, towed as much as 7,000 pounds over a thousand miles. Changed the oil in that diff once in 130,000 miles and never had any wear issues. This axle can handle the weight no problem. I really think the noise is in the front axle and the rear probably never needed the rebuild I did although it did show some age as it had 145,000 miles on it already. When I get a chance I will dig into the front axle, drain the oil and check for any metal as a first step. After the 1,000 mile trip at good speed I was pleased to see no oil had been consumed, the engine is running strong.

 

[West 1]

Put the truck up on stands and drained the front axle oil. Found metal on the drain plug. Oil only has 1200 miles on it so far. I remember finding some metal on the plug when I first bought it and changed the oils. At 145,000 miles I was not really concerned but now I will pull the diff and rebuild it. I expect pinion bearing damage but we will see. I tried to catch a good photo of the metal on the drain plug magnet. I looked at used Diffs locally for a quick exchange repair but they were either high miles or very expensive.
I ordered the bearings and seals and will rebuild mine. Then I know what I have and what shape it is in.

 

[West 1]

Pulled the front differential apart today. The driver side carrier bearing is the only one showing damage. I was sure it would be one of the pinion bearings but they were perfect. I will try and get pictures of the bad bearing when I can. Finally found the smoking gun for my on going whine on the highway.

 

[j91z28d1]

What ears are you guys using these days? I have a relic of a stethoscope plus mine from the hospital, but neither would help in this situation. Other than maybe checking my heart rate after seeing the bill for my race replacement.

I’ll be curious to see what condition my axle shafts are in and whether or not I have any damages. I know one of my seals is bad. Probably the side that had a blown out air shock, due to someone not starting the vehicle prior to loading a trailer full of weight. That was an exciting and expensive trip.

I have these. the price hurt but went from working what the noise was for a month, even as far as replacing a driveshaft that wasn't it. to pin pointing it within 30mins.

so justified the price for my sanity haha

Amazon.com

 

[West 1]

Very nice tool J, could have saved me time. I am OK with the rear rebuild. Had the leaking axle shaft seal and couple bearings were showing their age and probably did not have much more life in them. Now if I can get it assembled right the front and rear will be new.

 

[West 1]

Got the Front Diff apart and all clean yesterday, installed all the new bearings and assembled it today. Wasted 2.5 hours making a tool to adjust the carrier bearings. Could not see spending $175 for the special socket needed. My tool worked perfectly but lost time. The diff went back together really well. Pinion torque came in good, backlash is good and the gear pattern looks great so I got lucky only had it apart twice doing set up. Only found the one bad bearing on the carrier but all bearings were replaced including the axle stub bearings. In 2 hours more it could have been on the road again but I got tired and decided it can wait. I will try and attach pics of the bad bearing. I know the bearing race has weld on It now. It helps to weld the center of the bearing when removing a bearing from an aluminum housing. The weld shrinks the bearing race. Sometimes they just fall out after the weld but I did not get this one hot enough, it still popped right out. Hard to believe the little amount of pitting on that carrier bearing gave me the howl
in the differential. They need to be smooth to be quiet.

 

[West 1]

 

[j91z28d1]

the putting on that roller bearing is pretty bad. only time I've seen it that bad and the outer race looked OK. I cut the cage to see the inner and it was toast. looked really bad.

might be what you're feeling

 

[West 1]

I have no doubt that was my noise. Just a lot of work to make it quiet again.

 

[j91z28d1]

View attachment 464808View attachment 464809

I haven't been inside the front diff. how does. this. adjust side bearing load?

 

[West 1]

There is a Nut that the new tool fits, one on each side, in the 2007 and newer case the nut only has 3 spots to receive the nut. The older designs had more, maybe 12 spots so a different tool is needed. The carrier bearings float in the aluminum case until they are torqued in place. The threads on this special nut are on the outside and it threads into the housing, the tool tightens the nut from the inside. While you are setting the backlash you tighten the two nuts to center the ring gear where it needs to be. Once happy with the back lash you carefully go side to side tightening the two special nuts down against the carrier bearings. I believe final torque on these is 52 or 53 foot pounds but then you check the pinion to see how much torque it takes to spin it, there is a minimum and max for that also. I think it was 30-45 inch pounds to spin the fully assembled differential. Mine came in at 32, in spec but on the low side. So the three prongs which are 3/8" wide each slip into the special carrier nut so you can torque them. Once they are torqued and before you install the axle seals there is a special aluminum lock ring that has to be pressed into place against the carrier nuts so they don't come loose. Then the seals can go in and the axle stubs.

In this differential one of the aluminum lock rings had come loose allowing the carrier bearing on the driver side to get loose causing the damage you saw in the pictures. The owner probably ran it low on oil at some point causing the lock ring to fail but that is just a guess. There is no space around the carrier nut to use a standard type socket. You must have a tool like this to be able to do the final torque on the carrier nuts. I did not take many pictures just trying to get this job finished.

I know my welding skills leave a lot to be desired but the custom tool actually worked very well.

 

[strutaeng]

Great job find that one. Bearing certainly looks pretty bad.

If your welds hold and don't fail, then they are good enough! They look good to me. Is that Mig?

 

[West 1]

Yes with argon gas mix.

 

[Pressureangle]

I guess we're past the OP now, but if I saw those bearing races and housing marks I'd have spun the axles to see if they're bent. Those are typical galling marks from moving against the housing. That they're in only one place and equal on both sides is unusual, I got no theory.
Secondly, when setting up an old gearset with new bearings you'll have better luck with whine if you use the coasting side to pattern your lash. It's sometimes very hard to see your power side pattern once they're fully bedded in together, but the coasting side doesn't wear that much and is easy to see and match.

 

[West 1]

Just got home from the first test drive, now with the front and rear differential rebuilt, all new bearings and seals. All is finally quiet! The rear axle has about 1400 miles on it now and the front is only 50 miles but from idle to 90 mph on and off the gas it is quiet and smooth. Maybe the noise issue is finally dead and buried. Thanks to all for the consultations along the way. Still odd that the sound resonated and sounded like it was the rear axle until I had the car fully loaded front to back for our camping trip when it finally sounded like the noise was in the front.

The only shocker was my trip to the GM dealer to get new locks for the carrier bearings. Aluminum rings, not more than 1/8 wide by 2” round or so. $60 for 2. Why would these cost more than Timken Bearings for the Pinion I have no idea. I expected them to be maybe $5 for both. But I had to have them.

Heck found them on Amazon, $39 each??? https://www.amazon.com/8-25-Side-Be...rings+for+8.25+gm+differential,aps,163&sr=8-1

 

[dkad260]

@West 1 Glad you have it fixed, also nice DIY on the tool, I have a front diff waiting to be rebuilt and this might come in handy.

I changed many sets of bearings/axles before 14 bolt swapped in. Long story

FWIW, if anyone may not know, the 8.0, 8.6, & 9.5" (iirc) use the same axle shafts and axle bearings. Carrier is obviously different which likely adds beefier side and spider gears.

This axle can handle the weight no problem.

True, but 7K is not always the same. A 24' boat and a dump trailer with 2 yards of dirt can have a much different tongue weight. Excess tongue weight is what wears the axle shafts/bearings more than overall weight.

It's easy for the load leveling suspension to make it look like everything is fine if it gets too heavy.