: Root cause for the diff howl/whine?



Rockey
01-16-12, 05:41 PM
I just dropped my 09 V back off at the dealer because I noticed a very slight whine yesterday which turned into a more noticeable whine today. They seem to think it a wheel bearing but my money is on the diff. If so, this will be diff #2 for my V. I want to be prepared in case they deny warranty because of my mods. Maybe I will rebuild it myself and go with 3.73's if I have to go that route.

This sounded like a bearing issue to me but Im not familiar with GM diff's. I did a few gear swaps and rebuilds on a Mustang 8.8. I dont think its the gear contact because it whines on both the drive and coast side. If it is a bearing issue I will send the bearings to Nachis' engineering lab to have them analyzed. Maybe its the clutch pack? Doesn't seem likely though - no noticeable difference going around turns.

Maybe Im geting ahead of myself. I find it hard to believe they would deny warranty when it is pretty obvious this is an issue that exists at stock power levels, but if they do then so be it. Maybe its not even the diff, I just want to be prepared. Anyone have any input?

GM-4-LIFE
01-16-12, 05:51 PM
I had my diff replaced in December, but GM better find out why they are failing and get the supplier to fix them ASAP. This is going to cost GM a lot of money for no reason at all.

Gary Wells
01-17-12, 04:30 PM
There are / have been at least several posts / threads where the differential has gone south. Quite a few people have inspected the fluid level in the differential and found it to be low. If it is the differential, primary root cause would be the GM supplier, secondary root cause could be that GM does not inspect the fluid level when they come in from the supplier, and / or GM trusts the supplier to perform all quality control functions without a verifiable and / or accountable receiving inspection function. Only my thoughts on this possible issue, not saying that GM does not have good control of their suppliers.

Rockey
01-17-12, 05:00 PM
There are / have been at least several posts / threads where the differential has gone south. Quite a few people have inspected the fluid level in the differential and found it to be low. If it is the differential, primary root cause would be the GM supplier, secondary root cause could be that GM does not inspect the fluid level when they come in from the supplier, and / or GM trusts the supplier to perform all quality control functions without a verifiable and / or accountable receiving inspection function. Only my thoughts on this possible issue, not saying that GM does not have good control of their suppliers.

If the root cause is inadequate lubrication then it would be very difficult for them to deny warranty because of modifications. I was thinking it would be more along the lines of angular misalignment or improper preload/end play on the thrust bearing. I still havent heard fro the dealer so they probably didnt get a chance to look at it today.

Gary Wells
01-17-12, 05:31 PM
I'm only going by what has already been posted on this forum. Quite a few owners have either checked or had their dealer check the fluid level with the response being that the level was low. I don't remember anybody reporting that diff was their replaced for this reason. Several people have reported their diff going out & being replaced due to any particular reason that I remember. So it could very well be what you suspect / suspected. Good luck with your dealer & repair / replacement either way.

mrk4543
01-18-12, 08:21 AM
My diff was replaced by my local dealer, Tropical Cadillac in Bradenton, just last week (2011 CTS-V, automatic,, delivered new on 7/15/11 with 5,400 miles now on the clock). Dealer went thru GM check list of possible causes for the whine and they, along with the GM Drive Train folks decided it was the diff. Supposedly the cost to GM for the warranty replacement was around $3,000. It would definitely be interesting, and in GM's best interest to determine the root cause....it would surely eliminate a lot of concern by customers as well as a cost saving to GM.

Rockey
01-18-12, 08:38 AM
I'd bet dollars to doughnuts that GM already knows the root cause of this problem. I was hoping someone here would know and be able to shed some light on it for us.

RogersV
01-18-12, 10:00 AM
I'd bet dollars to doughnuts that GM already knows the root cause of this problem. I was hoping someone here would know and be able to shed some light on it for us.

Received my V on 1-17-09, had "Differential Carrier Assembly" replaced on 9-21-09 at 6928 miles. At the time the dealer thought they would get permission to repair, but G.M. said no, return Carrier Assembly intact so they can evaluate the problem. By now it's only fair to say they know what's causing the failures.

mrk4543
01-18-12, 11:17 AM
Received my V on 1-17-09, had "Differential Carrier Assembly" replaced on 9-21-09 at 6928 miles. At the time the dealer thought they would get permission to repair, but G.M. said no, return Carrier Assembly intact so they can evaluate the problem. By now it's only fair to say they know what's causing the failures.

I would hope that they know but you would think that it wouldn't take almost two years to remedy the problem. I know, big business moves slowly but this particular issue is ridiculous.:thepan:

Gary Wells
01-18-12, 12:43 PM
Getting approved suppliers / vendors / manufacturers is pretty much the bane of the aerospace industry ever since there's been vendors / suppliers / manufacturers existed.
Probably has been a major issue for the auto industry too. A lot of politics involved at that level between purchasing depts. and vendors.