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Differential Noise

springfield

By springfield
in Ask A GM Technician

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springfield Enthusiast

springfield

Posted
Posted

Hi everyone,

 

I have a differential noise that I have recently noticed on my Suburban. My Sub is a 3/4 ton with the 8.1l so it has a full floating axles. This noise is not apparant below 20 miles per hour. The noise increases in intensity from 20 mph on up. The best way to describe the noise is a rather high pitch whine / ringing that some times sounds like a rotor or a drum being turned on a brake lathe. It does not change during acceleration or deceleration but is only speed sensitive. To make it more odd, you don't always hear it through the entire speed range. You may hear it at 55mph while cruising but not 65mph while cruising. Or, you may accelerate from a stop up to 75mph and hear it the entire way. This noise is not extremely loud, but is definately not normal. I ran the truck on a lift at a bout 25mph or so and it seems the noise is centered around the rear of the drive shaft near the u-joint and you can hear a slight gear / bearing noise from the differential. In the back of my head I keep thinking that it may be the pinion bearing, but shouldn't the noise change from acceleration to deceleration. Also, I have never heard of a u-joint making that kind of noise but is this a possibility? I have heard u-joints making noise in forward or reverse but not a constant noise like I have. Ultimately I guess I will just have to tear into it to find the culprit, I would just like to know if anyone has had similar experiences?

 

Thanks in advance for any help.

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

While pinion bearings can be load sensitive, for noise, they usually just make noise that is consistant with propshaft speed.

 

Also in that axle, there is a pinion support bearing that is lightly pressed into the axle hosing that supports the gear end of the pinion. I have seen a few of those make noise as well.

 

This is a super simple axle to work on. To just check the three bearings in question all you have to do is drain the diff, remove the rear propshaft and remove the pinion support housing bolts that are placed around the pinion flange. Then, remove the pinion support housing from the axle housing, seperate the pinion flange from the pinion, seperate the pinion from its support housing and you will have all three there to inspect visually.

springfield Enthusiast

springfield

Posted
  • Author
Posted
While pinion bearings can be load sensitive, for noise, they usually just make noise that is consistant with propshaft speed.

 

Also in that axle, there is a pinion support bearing that is lightly pressed into the axle hosing that supports the gear end of the pinion. I have seen a few of those make noise as well.

 

This is a super simple axle to work on. To just check the three bearings in question all you have to do is drain the diff, remove the rear propshaft and remove the pinion support housing bolts that are placed around the pinion flange. Then, remove the pinion support housing from the axle housing, seperate the pinion flange from the pinion, seperate the pinion from its support housing and you will have all three there to inspect visually.

 

Hi,

 

Thanks soo much for the reply. So the pinion bearing should be a high pithched noise because of the RPM while the carrier bearings should be a low growl that you traditionally attribute with a worn bearing right? Also, when the unit is dis assembled, will the bearing have noticeable wear or feel notchy like any other worn bearing? I guess the high pitched noise is what is throwing me off. I agree about the design of the diff, I was kind of excited to see that I could simply un bolt the pinion housing and remove it from the front.

 

Thanks again for your reply!

 

 

I forgot to ask if this is some what of a common failure?

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

A bearing noise is a bearing noise. From what I've ever seen, if it's higher pitched, is more than likely spinning fast and smaller in size. Carrier bearings would be load, possibly directionally, sensitive.

 

Can't say that I've seen these fail a lot but a few over the years.

springfield Enthusiast

springfield

Posted
  • Author
Posted
A bearing noise is a bearing noise. From what I've ever seen, if it's higher pitched, is more than likely spinning fast and smaller in size. Carrier bearings would be load, possibly directionally, sensitive.

 

Can't say that I've seen these fail a lot but a few over the years.

 

 

Yeah, I keep thinking that I should be able to see some play in the yoke on the front of the pinion, but there is none that I can visually see. I think because the axle is full floating that I wouldn't be able to see a difference while loading one side or the other.

 

Thanks again.

  • 1 year later...
springfield Enthusiast

springfield

Posted
  • Author
Posted

Since I hate starting threads and not giving a conclusive post....here are my findings. My Suburban has the 10.5" 14 bolt differential in the rear. Upon taking the rear cover off, I found the right side carrier adjuster lock pin and bolt stuck to the magnet in the bottom of the case. this had caused the right carrier bearing to fail :banghead: . I ordered replacement parts online and will start putting it back together hopefully this weekend. This time a little blue locktite may find its way onto the bolts that hold the adjuster pin! Anyway, I am glad I am not crazy and that I found the failure. I thought it was nice to find a drain plug on the case so that I did not have to take the cover off. In my case, taking the cover off earlier may have saved me a major headache. If any of you are changing diff fluid in the future, you may want to check that all fasteners are torqued.

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