Great News - I get to swap my rear axle!

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unixadm

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I just picked up my 2000 Yukon XL 1500 SLT 4x4 about two weeks ago... maybe a bit longer. Very clean, good running ride with 142k on it. Took it on a 15+ mile test drive, drove great. No problems for the first week and a half (700+ miles), then on my way to work one morning I started noticing a noise in the drive-train. I knew immediately it was a bearing noise, and those are NEVER cheap.

Had one of the guys at work drive, while I crawled around and listened. Sounded like the rear differential, but possibly coming from the NP246 transfer case. Decided to go to the local GMC dealer here in Elk Grove and have them check it over today. SA was cool, and the differential tech was also really cool. We took it on a road test where the noise was duplicated, but their initial suspect was the front diff. All he said was "That's gonna be expensive!". I just had to laugh at that, at least he's honest. After driving more, we both agreed on what I said when I showed up, rear diff or transfer case. So he put it up on a lift with another tech inside, and the noise is coming from the rear diff. Both the passenger side wheel bearing and the pinion bearing. He also said it looked like the diff had been over heated. I noticed the paint chipping away as well and thought the same, but then again it does not look to have ever towed anything.

A rebuild would be around $1300 at the dealer, and it needs a new POSI. Found a complete assembly locally for $700 with 42k on it, so I'm going to pick that up and install it.

The tech also checked my front diff and it has a fair amount of metal on the magnet. So it's just a matter of time before it craps out, and that's a $1,000 job to rebuild. They said it was a good idea to pick up a used rear diff, because he said he sees 20 failed front diffs for 1 rear diff. But for the fronts, he said even the low mile aluminum case diffs can go bad or have bearing issues with very low miles, so picking up a used one may net me nothing. They seemed pretty straight up, even pointing out some other issues with the Yukon for free based on past experience. Knowing the front diffs are crap, I'll take his word and just pay for a complete rebuild at the dealer or another shop if it starts making noise or leaking. So far, it seems quiet without leaks. I'll do a full service on everything while I'm down there.

So now I have to get the axle here, do a service on it, check the brakes, etc. I had ordered the GM parking shoe kit because my parking brake does not work. So I guess I can install that, and the rear brakes had just been done so if the rotors are showing their age on the replacement, I can swap those over as well. Hopefully I can knock it out in 4 hours with air tools in my garage. I have not swapped one since doing it on my 1994 Impala SS.

I was hoping for the transfer case, but something tells me it won't be long before I'm screwing with that too. Thankfully there are lots of these at recyclers so good used parts are pretty easy to come by.

I was going to get some 2007+ 20" Yukon XL wheels and tires for $1200, but I guess now my Yukon money is going to repairs. Not a big deal, I'd rather have it be reliable than have a little more bling. Damn 10 bolts, I hate them.
 
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unixadm

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Took four hours to install a replacement from a 2002 Yukon XL by myself with the Yukon on jack stands. Problem solved. You guys sure don't say much on this forum, but hey if you start getting an annoying howl coming from the rear end, well you'll know what needs to be done.
 

rigo_jones

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yeah usually when the diff is about to go out it makes a noise. did it had fluid when you removed the diff? just wondering how it over heated.
 
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unixadm

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It had fluid in it still. Not sure how it was over heated - perhaps someone got it stuck and it cooked the posi. It did look like it had gotten hot. I also noticed above average resistance on the yoke when trying to turn it after I pulled it out.
 

Robert.K

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So Im having this weird grindind noise from the rear of of my truck. posted a thread for help. not sure if its the same that your talking about, but i know nothing about that type of stuff. What should i look and listen for to understand if my differential is going bad?
 
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unixadm

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Is the noise constant? Typically differential noise will change with application of throttle and the release of the throttle. You can also get up to speed (50-55) and then down shift into (3) to create more engine braking. On my Yukon XL, it would make a audible grinding/whining sound that varied if you were on the throttle or off the throttle. If I was coasting at 50 and shifted into neutral, the noise would go get much quieter (less driveline loading). Have someone drive while you crawl around with your ear to the floor listening. Mine would start at around 20 MPH and keep going until road and wind noise would begin to make it less audible.

Any grinding noise from the drivetrain is BAD. If you cannot troubleshoot it, take it to a dealer to get it diagnosed. Be cool with them and see if you can follow your vehicle to the service bay to make SURE the noise is coming from a particular component. It can be anything from brakes, parking brake, wheel bearings, CV joints (4wd), transfer case (4wd), U-joints, or the differentials themselves. The G80 posi can crap out too and cause noise. I'm a pretty competent mechanic, but I don't have a lift. I was 95% sure it was my rear diff, but I paid the dealer a discounted $60 just to confirm so when I bought the part I knew it would solve the problem. Drivetrain noises can also propagate through the drivelines to carry the noise to another component.
 

J-Will

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Took four hours to install a replacement from a 2002 Yukon XL by myself with the Yukon on jack stands. Problem solved. You guys sure don't say much on this forum, but hey if you start getting an annoying howl coming from the rear end, well you'll know what needs to be done.

we talk on here. we just have a lot of ppl that show up and ask a question, get help, then split. get into some of the threads and make a name for yourself here. were all more than happy to help a buddy. happy to hear youve got it all straightened out tho. my 97 trans am has the 10 bolt. and its howling like crazy right now. i just picked up some yukon 373 from my local shop.. getting the crush sleeve, bearings, and shims tomorrow. yay.... guess what i get to do sunday. lol if it doesnt shit out on me before then.

btw. welcome to the forum.
 

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