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Discussion Starter #1
I have a 2008 GMC Yukon that is making a noise in the rear end, and need a little help deciding if this may be a DIY fix or just take it to the shop. I've done a lot of DIY, mostly on cars. The noise sounds to me like a whine/groan like I might expect a wheel bearing to make. Observations so far:
  • The noise audible from low speed, and gets louder as speed increases. It's proportional to speed, not engine RPM.
  • Steering right and left doesn't seem to change the noise (my attempt to see if it could be a wheel bearing)
  • Noise is worse when moving forward than reverse
  • The noise changes when transitioning off the gas to coasting
  • The noise is there regardless of whether it's in Drive, neutral, 2WD, AWD. It may change a little with each setting, but mostly the same.
  • I rotated the tires front to back to rule out tires noise. No change from doing that.
  • The noise is definitely in the rear. I put the back up on jackstands and had someone step on the gas. Noise is clearly from the back, in the middle.
  • I also put my phone under the rear of the vehicle in different places to try to capture exactly where the noise is coming from. I recorded under the differential housing, the driveshaft, and under the ends of the rear end to check if it was wheel bearings. It seemed loudest directly under the diff housing.
  • There is a small oil leak at the nose of the rear end where the driveshaft attaches
The noise got worse a few months ago while towing on a road trip, and it puked trans fluid out the breather. I had a shop look at it while I was on the road. They said they opened the rear end and said it looked OK, and refilled. No change to the noise after that.

Could this be ring & pinion, or a bearing in the rear end? I'm not familiar with the noise a bad driveshaft would make, but could it be that?

Thanks for your input!
 

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Block the front wheels. Mark the driveshaft to rear yoke orientation and remove driveshaft from rear axle. Slide it out of the transfer case and lay it on the ground. Now, oscillate each joint. They should fully oscillate smoothly and with very little resistance.

With that said, it could be either the universal joint or the pinion bearings.
While the shaft is out, the yoke on the axle should have little to no play, both vertically and for and aft.
 
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Discussion Starter #3
Thank you for the suggestion. I detached the rear portion of the driveshaft. The U joint seems to articulate smoothly. I also attempted to move the yoke at the front of the rear axle housing, and don't detect side to side or fore-aft play. I do detect rotational play however, and I heard some noise too. Rather than try to describe it, I figured a video (see below) would tell the story better. Thoughts?

 

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Discussion Starter #4
Any input appreciated :) thank you
 

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I assume the noise in the rear axle is either the ring & pinion or a bearing. Possibly caused by a slow fluid leak that I did not notice until it was too late. Is there a way to distinguish bearing vs. ring & pinion, short of disassembly of the axle?

Scott
 

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Take off the rear diff cover and look at the ring and pinion, I would see what happens when you move the yoke back & forth and see if you can narrow down that noise. You are only out a couple of quarts of diff fluid and a gasket by doing this. If the gears are chewed up or excessively worn then...that might be your problem. That sounded like a lot of slop in that rear end in your video. 1/2 rear ends are known for failing. If you have never rebuilt one I would take it to a shop if you are not able to rebuild one your self. I would do it pretty soon before it shatters on you. I did that to my front diff on my dually and it made a mess.
 

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It sounds like you’re experiencing a worn bearing. As far as diy or not, depends on your experience and your confidence in getting the correct play in the pinion gear. Too much and you’re creating excessive heat and wear on your gears, and too little will cause the gears won’t have sufficient contact and wear quickly.
 

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Discussion Starter #8
Thank you for the input. Does pinion depth and/or backlash need to be checked after replacing bearings?
 

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Yeah, those are the measurements I was talking about. You can use a crush washer or spacers to get the correct backlash.
 
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