Noise in driveline, pinion bearing?

[dkad260]

2012 Yukon XL Denali AWD.

I have had this driveline noise for a little while, seems to be slightly more noticeable and I'm not sure what it is, my guess is maybe the pinion bearing.

Short history, it has 120K miles, bought it with 90K, all service is documented at dealer. When I bought it, I replaced both diff fluids, and transfer case fluid.

The rear pinion was wet but not dripping, it later started to drip and I had the rear pinion seal replaced.

Recently I had both driveshafts balanced with new U joints in both shafts, also both front hub and bearings.

I have new axle shaft bearings I'm going to replace but haven't got to them yet. My guess is maybe the diff was ran low by the previous owner at one point, not sure

This noise is most noticeable under a slight load above 50 MPH, this audio is from 70-75 MPH.

It's a pulsating, higher pitched noise about every 1.5 sec, like a sine wave.

I took the audio with a stereo Sennheiser mic in the drivers footwell with the gain turned up a bit, you may have to turn the bass down a little if poss, but the noise is there after a few seconds.

 

[OR VietVet]

You said an interesting thing about the rear pinion seal replaced. I was in shops where I found out later that when the pinion nut was removed and yoke pulled and seal replaced and then yoke reinstalled, the techs were "winging it" so to speak when they reinstalled the pinion nut. The way I was shown and did was that before I removed the nut I measured from the tip of the pinion threads to the top of the nut. I then scribed the end on the shaft, the nut, the yoke and down to the diff housing. When I put back together I made sure it all lined up and the same measurement from the tip of threads to the top of nut was the same and I verified there was no binding or slop and that it turned easy. If the tech that did your seal was not that careful, that could explain why you may have a pinion bearing noise.

 

[dkad260]

If the tech that did your seal was not that careful, that could explain why you may have a pinion bearing noise.

Yeah, that's the only part of this that gives me worry. The shop that did the seal, has experience with this as they have been racing for 40 years, and have set up many rears. However.....that doesn't mean the tech who did the job was careful enough so I agree your concern is very plausible.

I do need to verify it's coming from the rear diff, as opposed to the front, my gut says the rear though.

 

[drakon543]

i have no experience with this but i have a story i sure someone will get a good chuckle from.
so i had a guy asking to borrow tools so he could change his pinion gear and bearing. i told him id only have the sockets he needed not the tools to set the spacing to have proper backlash. he proceeded to tell me thats all he needed because the "new stuff" will properly seat itself. i tried to argue with him but he insisted all he had to do was tighten it "until you couldn't" then back it off a 1/4 turn. so because im a ***** i caved and just lent him the tools he requested. couple of days later he was driving it around and i could hear his gears halfway down the street screaming. he says what should i do i think you were right.

 

[OR VietVet]

i have no experience with this but i have a story i sure someone will get a good chuckle from.
so i had a guy asking to borrow tools so he could change his pinion gear and bearing. i told him id only have the sockets he needed not the tools to set the spacing to have proper backlash. he proceeded to tell me thats all he needed because the "new stuff" will properly seat itself. i tried to argue with him but he insisted all he had to do was tighten it "until you couldn't" then back it off a 1/4 turn. so because im a ***** i caved and just lent him the tools he requested. couple of days later he was driving it around and i could hear his gears halfway down the street screaming. he says what should i do i think you were right.

"i think you were right", yep, I think you were right, too. Surprised that it did not lock up. Those diff's can get hot enough that the pinion bearing race will be gaulded or a new one would just fall in there.

 

[Donal]

2012 Yukon XL Denali AWD.

I have had this driveline noise for a little while, seems to be slightly more noticeable and I'm not sure what it is, my guess is maybe the pinion bearing.

Short history, it has 120K miles, bought it with 90K, all service is documented at dealer. When I bought it, I replaced both diff fluids, and transfer case fluid.

The rear pinion was wet but not dripping, it later started to drip and I had the rear pinion seal replaced.

Recently I had both driveshafts balanced with new U joints in both shafts, also both front hub and bearings.

I have new axle shaft bearings I'm going to replace but haven't got to them yet. My guess is maybe the diff was ran low by the previous owner at one point, not sure

This noise is most noticeable under a slight load above 50 MPH, this audio is from 70-75 MPH.

It's a pulsating, higher pitched noise about every 1.5 sec, like a sine wave.

I took the audio with a stereo Sennheiser mic in the drivers footwell with the gain turned up a bit, you may have to turn the bass down a little if poss, but the noise is there after a few seconds.

So, what are you going to do? Jack up both rear wheels, remove the drive shaft, check for free movement of yoke, back and to, tighten nut slightly until no movement can be felt. Rotate the yoke, a small resistance, may be enough. assemble, road test. A short road test at first. comeback and check temperature of housing neck. The torque required to rotate the yoke as a test is published, but escapes my memory at the moment. But is included in service manuals. I am have time to look it up later..

 

[Geotrash]

2012 Yukon XL Denali AWD.

I have had this driveline noise for a little while, seems to be slightly more noticeable and I'm not sure what it is, my guess is maybe the pinion bearing.

Short history, it has 120K miles, bought it with 90K, all service is documented at dealer. When I bought it, I replaced both diff fluids, and transfer case fluid.

The rear pinion was wet but not dripping, it later started to drip and I had the rear pinion seal replaced.

Recently I had both driveshafts balanced with new U joints in both shafts, also both front hub and bearings.

I have new axle shaft bearings I'm going to replace but haven't got to them yet. My guess is maybe the diff was ran low by the previous owner at one point, not sure

This noise is most noticeable under a slight load above 50 MPH, this audio is from 70-75 MPH.

It's a pulsating, higher pitched noise about every 1.5 sec, like a sine wave.

I took the audio with a stereo Sennheiser mic in the drivers footwell with the gain turned up a bit, you may have to turn the bass down a little if poss, but the noise is there after a few seconds.

A pinion bearing usually develops a very prominent growl, in my experience. You might try sitting in the backseat while someone else drives and see if it’s louder from back there.

 

[swathdiver]

Before taking it apart:

Before putting it back together:

Remember that there is a crush washer in there to keep tension on the pinion and once the nut has been loosened, the tension is lost so we must tighten it just a little more next with a NEW pinion nut. The shop manuals always show this being done manually but youtube shows most people using an impact gun.

 

[dkad260]

So, what are you going to do? Jack up both rear wheels, remove the drive shaft, check for free movement of yoke, back and to, tighten nut slightly until no movement can be felt. Rotate the yoke, a small resistance, may be enough. assemble, road test. A short road test at first. comeback and check temperature of housing neck. The torque required to rotate the yoke as a test is published, but escapes my memory at the moment. But is included in service manuals. I am have time to look it up later..

I won't get to it today, but will dive into tomorrow hopefully. My luck will be it's too tight and I would need to replace the crush sleeve and likely the bearings, or rebuild the rear.

A pinion bearing usually develops a very prominent growl, in my experience. You might try sitting in the backseat while someone else drives and see if it’s louder from back there.

I can't tell for sure but under a good load if there is a faint growl starting, it might be masked by the exhaust. That leads me another topic I've been meaning to bring up. The exhaust looks OE but it seems like it has a little more bark than other 6.2 GMT 900's I've heard. Steady cruise is quiet, but under acceleration it has a nice exhaust note..or how crazy would it be that it's actually a pinion.

Before taking it apart:
View attachment 403343

Before putting it back together:
View attachment 403344


Remember that there is a crush washer in there to keep tension on the pinion and once the nut has been loosened, the tension is lost so we must tighten it just a little more next with a NEW pinion nut. The shop manuals always show this being done manually but youtube shows most people using an impact gun.

Thanks for that.

For the 8.6", does this rotational torque include the axles or with them pulled? Or just the calipers removed?

 

[dkad260]

A pinion bearing usually develops a very prominent growl

This is something I may have overlooked. Have experienced many front hub and bearings sounding like you have mud tires when they are worn, I will focus a bit more on any growl or roughness.

 

[dkad260]

Now that I am more focused on the "growl" over the exhaust note, I'm almost certain that's what it is. Been busy last couple days so haven't been under it, hopefully by Saturday evening I will have this narrowed down.


Local shops around my area that specialize in drivelines are all around $1500 to rebuild the rear. I'm mechanically inclined enough to do this, I just haven't done one, can't be much harder than rebuilding an engine right?

I will pull the rear cover this weekend and take a look, will likely get a new set of OE ring and pinion gears and a master rebuild kit with setup bearings...the whole works. I have a vacation coming up and this would be a good stay-cation experience.

Will probably pull the axle for this as that's a piece of cake to do, and would make the job much easier.

Don't want to put the cart on front of the horse yet, but this is looking where it's going.

 

[j91z28d1]

just my experience, but unless you feel some slop in the pinion flange, and even then the gear whine starts before bearings, unless they are really bad like bad enough to see metal on the magnet, and not just the paste metal, gritty stuff.

I wouldn't be surprised if it's something else, I've had outer axle bearings roar thou.

I mean they would have had to straight impact the pinion nut down enough you could bearly turn it by hand for it to kill bearings sitting on oil. just what I've seen over the years. hopefully you find it. my first guess till I heard it was drive shaft, they can resonate like that but yours is more of a roar where a drive shaft is more of a hum.

 

[j91z28d1]

oh the tq spec for the pinion bearing drag is always listed without the ring gear in the axle. with the correct tools you measure it all up to get pinion depth shims thickness without needing the carrier in it. then you tighten the pinion nut till you get the drag torque spec and then install the carrier and shim side to side for back lash.

without the right tools. you either get lucky or assembly and disassemble 10 times lol.

 

[OR VietVet]

Find a trusted tech/shop and drain all the fluid and cover off and measure the gear lash and check the wear pattern. I was a little worried about mine and a "noise" and me and my friend stayed late one night at his shop and checked all that and the lash was in the middle of the desired readings and pattern looked good. New fluid and I went on a 15 day 5500 mile trip with no problems.

 

[dkad260]

I took it to a very reputable shop this morning, they put it on a lift and we looked at the rear axle, transfer case, front diff, all the axle bearings....they said it sounded good. The RR axle bearing had a hint of noise but nothing alarming...I plan to change those soon anyway.

Going back a month, I replaced my rear u joints and bent one of the ears slightly, so I took it to a shop and had both my driveshafts balanced and new U joints installed....all was good. I was surprised both shafts needed about 2 ounces of weight but it ran smooth.

When it was on the lift today, I could see both the driveshafts have noticeable runout....and it looks like alot.

The shop that balanced the shafts assured me the shafts were straight and balanced, but I could easily register .060" runout on the rear shaft with a dial gauge and it's likely a little more. The front has more runout but was too hot to get anything setup to measure around the converter.

I wiggled the yokes, used a prybar, and both front and rear driveshaft yokes are good and tight, no movement up or down.

I didn't think it was the driveshafts because I had a slight noise before as the rear u joint had slight movement, and it morphed into this, coupled with the rear pinion history.

How much "wobble" is normal? Should I be able to see it from 10' away lol?

 

[dkad260]

I've seen a number of drive shafts spin when they're in the air but I don't remember them ever looking like this...maybe I'm wrong.

Something must have popped loose inside when they welded the weights, that's the noise you can hear Inside the shaft. Wouldn't surprise me the welder was too hot and there's a piece of slag inside.

 

[donjetman]

yeah that can't be right

 

[j91z28d1]

I hate to say it, but I think I'd buy 2 new shafts of the best quality you can find since oem seems to be discontinued.

I'm no expert, but I would think that spinning at 80mph would be ******* everything, especially the tranny tail housing bushing. the pinion has a bearing but the tranny is just a bushing that's splash oiled I believe.

I don't know if it's the same as the old manual trannys, but I killed a few of those with vibration, took them down to the copper under the sliver/Grey coating. not sure if you can see it with the shaft out or not to inspect it.

 

[j91z28d1]

it sure seems to me that oem gm driveshafts are not meant to be serviceable. I think you have to melt that epoxy out to get the old ones out without damage and then the amount of heat needed is ******* the shaft.

 

[OR VietVet]

it sure seems to me that oem gm driveshafts are not meant to be serviceable. I think you have to melt that epoxy out to get the old ones out without damage and then the amount of heat needed is ******* the shaft.

I beg to differ. I have changed many pairs of u-joints and heated the keeper/epoxy to melt it out. The heat is not that much really. You are not heating it like you are getting ready to cut metal.