Could a CV axle be the cause?

[Mr T]

Folks:

I've posted a bit about an odd noise in the past....still considering what could be the cause before I get too into the project. A few facts first:

Vehicle:
- 2008 Denali XL (6.2L, of course) AWD.
- 198K miles
- All drive line oils changed every 30K (Tranny, transfer case, front and rear diff).
- At 182K miles (last July) I replaced front and rear diff oils. No abnormal shavings in the front.
- At 190K, while replacing the upper control arm on the left side, I ended up replacing the CV axle as when I dropped the knuckle, I let it fall too far and the CV came apart. I couldn't get it back in so I simply bought a new one from O'Rileys.
- Both left and right hubs are relatively new (15 to 20K on each).
- 2 weeks ago, with wheels in the air on stands, I got under the truck and checked all drive lines. All felt tight (no side to side wobble) and from what I could tell, looked normal. I'm no drive line expert!

As of last month, I started to get a whirling noise from the front end--very faint. Only audible when between 25 to 45 MPH and ONLY under power. Take the gas off and it goes away. It's more rhythmic. wobble noise and not a constant sound like a wheel bearing.

All of this lead me to believe my possible issues are:

1) Carrier bearing on the front differential. I say carrier cause it's not grinding or loud, so probably not the planetary gears, just a bearing.
2) Because I replaced it recently, COULD it be the left side CV Axle is going bad? I know what a CV axle does when it's "gone", meaning no more grease and someone is turning sharp and you hear the thud or crackle. What about the axle just being noisy under power and when straight? Is that possible? Could I have put a replacement in that is flawed and is now going bad after just 1 or 2 months?

Thoughts?

 

[swathdiver]

Folks:

I've posted a bit about an odd noise in the past....still considering what could be the cause before I get too into the project. A few facts first:

Vehicle:
- 2008 Denali XL (6.2L, of course) AWD.
- 198K miles
- All drive line oils changed every 30K (Tranny, transfer case, front and rear diff).
- At 182K miles (last July) I replaced front and rear diff oils. No abnormal shavings in the front.
- At 190K, while replacing the upper control arm on the left side, I ended up replacing the CV axle as when I dropped the knuckle, I let it fall too far and the CV came apart. I couldn't get it back in so I simply bought a new one from O'Rileys.
- Both left and right hubs are relatively new (15 to 20K on each).
- 2 weeks ago, with wheels in the air on stands, I got under the truck and checked all drive lines. All felt tight (no side to side wobble) and from what I could tell, looked normal. I'm no drive line expert!

As of last month, I started to get a whirling noise from the front end--very faint. Only audible when between 25 to 45 MPH and ONLY under power. Take the gas off and it goes away. It's more rhythmic. wobble noise and not a constant sound like a wheel bearing.

All of this lead me to believe my possible issues are:

1) Carrier bearing on the front differential. I say carrier cause it's not grinding or loud, so probably not the planetary gears, just a bearing.
2) Because I replaced it recently, COULD it be the left side CV Axle is going bad? I know what a CV axle does when it's "gone", meaning no more grease and someone is turning sharp and you hear the thud or crackle. What about the axle just being noisy under power and when straight? Is that possible? Could I have put a replacement in that is flawed and is now going bad after just 1 or 2 months?

Thoughts?

Could be the aftermarket CV shaft, might be the ring and pinion. Can you record and post the noise for us? Mine sounds the same even in 2WD but engine load does not matter. Not too worried about it yet, still not sure of what it is either.

 

[Foggy]

What you are describing is usually NOT a CV axle noise/symptom, so
I doubt it's the CV. Possibly bad wheel bearing, but you know how to
diagnose that by driving and putting load from left to right to see
if it changes.
My guess would be the diff... sorry

 

[Big Mama]

My Dad’s 06 Silverado does the same thing on the right side. His sounds like a loud tire tread buzzing but drops off at around 50 mph. Did you get an alignment after the front end work?

 

[Mr T]

So wait! I had a thought today while cleaning bathrooms.....yeah....that's when I do some of my better thinking.

I can't really figure out the cause of the noise; however, to eliminate or confirm it is the front diff, why not simply disconnect the driveline that runs from the transfer case to the front diff? If the noise stops, it is either the diff itself or the u-joints in that drive line. Right? And we know what u-joints sounds like.

SO to my KEY question. Does anyone know if doing so could damage the transfer case? I can't see how it would hurt the diff but the transfer case, could this cause a "balance" issue, if you know what I mean.

Thoughts?

 

[Mr T]

Wanted any thoughts if anyone has an opinion on the matter. Thx.

 

[Big Mama]

Shouldn’t cause any problems but if you want to make sure it goes back the same way put a mark on the shaft and a reference point. With it out you’ll be able to see if you have bad u-joints.

 

[LRob]

Dont see why it would hurt to pull the front drive shaft to take a wuick drive to try and recreate the noise. Do a little more research though and let us know. This is just theory unless someone has actually done it. I have 2wd so no real experience with it.

 

[Mr T]

Shouldn’t cause any problems but if you want to make sure it goes back the same way put a mark on the shaft and a reference point. With it out you’ll be able to see if you have bad u-joints.

Always a good suggestion. Something easy to forget when trying to get things done quickly. Thx!

 

[Moose912]

DO NOT ATTEMPT TO DRIVE AN AWD DENALI WITHOUT FRONT SHAFT!! IT WILL DESTROY THE TRANSFER CASE.

 

[Big Mama]

Thanks Moose you may have saved someone a pile of cash, what causes the failure?

 

[Moose912]

The differential in them is designed to have consistent load and continuous revolution. When it cant match that, it trashes the gears. (This is what I have been told). I looked a year ago at doing this to dyno my truck for tune, but was advised by multiples of this. Couple guys said you could cook it in under 10 minutes. Way I see it, if its even a 1% chance its possible, hell no.

 

[Big Mama]

Forgive my ignorance. He was going to remove the shaft and drive around the block so the front wheels are turning as is the output on the TC but I suppose there’s a chance one could spin more than the other. 1% is too much of a gamble for me too.

 

[Moose912]

No ignorance there sir. We are all in this together and trying to learn what we can as we go!!

 

[andyd]

What you are describing is usually NOT a CV axle noise/symptom, so
I doubt it's the CV. Possibly bad wheel bearing, but you know how to
diagnose that by driving and putting load from left to right to see
if it changes.
My guess would be the diff... sorry

I would also agree i had a simular issue and I purchased a used diff knowing it would need a rebuild. While rebuilding I discovered that the outer snub shaft bearing were shot along with the outer carrier bearings. They were not that bad but I did get the noise you described.