To replace the whining differential again?

Slithering_Joe · #1 (**permalink**) 07-13-09, 11:26 AM

- How many of you guys have a rear differential that whines and are living with it?
- How many ’06 & ’07 CTS-V owners experience gear whine?

I’m wondering if I am going to be wasting my time taking this car in for the 6th time to the dealership for more warranty work. Thankful for a warranty which expires this September but this is getting old and I really like this car. I would hate to have to bring this car in to fight with a dealer or to have the replacement for the replacement diff whine again in just a few thousand miles. I’m more worried about getting a diff that becomes worse than the previous one. Not once since owning the car had I caused the backend to hop or did I beat on it in anyway. I guess I would just like some reassurance that this rear will not let me down someday while on the road or when I am long outside of the warranty period, diffs becomes scarce and expensive. With a child on the way I need some reliable transportation and peace of mind.

History: Back in October ’08, I had the original differential replaced (odometer: 25,000 miles) for a whining sound that occurred all the time. After ~3,000 miles the replacement diff started to whine but under different circumstances than with the original one. Because of this, I changed out the original GM ‘grape oil’ with Amsoil Severe Gear Lube 75W-90. Since then, I have accumulated another 5,000+ miles and it has done nothing to improve it. With this diff (odometer: 33,000 miles), applying very light throttle acceleration or slow deceleration (engine braking ) the whine is quite audible. Accelerating and decelerating have different sounds where at a slight acceleration it is much more audible. But, when you apply more throttle (faster) the whine goes away. If you are on the highway with the cruise control on the rear is whisper quiet. One thing to mention is that the diff only whines after it has had a chance to heat up from use. Weird huh? The sound is quite annoying especially since I had never owned a car that did this and I expect more from this car.

- Is this a normal thing with these diffs?
- Is this the signs of a dying diff?

I’m wondering if the reason for the noise is in the way the higher ratio V differential is suspended by its subframe. This is my first idependent-rear drive car but previous cars had 4-link straight axles and I never heard them. I have also read numerous posts from members here mentioning that after changing out their factory bushings for stiffer poly bushings they noticed more gear whine. Could the stiffer bushings may dampen less vibration from the gears contributing to the audible whine? Sounds plausible.

- Or, is it a suspension design that transmits more gear noise to the chassis?
- Maybe this design transmits more gear noise to the chassis/body than with other independent suspension designs?
- If this is the case, I and others may have nothing to worry about. Correct?

The dealership is trying to sell me a GM warranty for $2000 - $3000 which I think is insane! I have time until Sept. to shop around for a warranty or a new car.

ahahnu · #2 (**permalink**) 07-13-09, 11:32 AM

Come to Wycoff on Wed. Hopefully others will show and we can commitee the decision! Go for rides and compare noises.

lollygagger8 · #3 (**permalink**) 07-13-09, 11:36 AM

Very, very, very normal. (search and you'll find many threads)

Try different fluid other than the GM garbage. Also, heavier fluid 90w140 seemed to quiet mine down a bit.

Slithering_Joe · #4 (**permalink**) 07-13-09, 12:14 PM

Quote:

Originally Posted by lollygagger8

...
Try different fluid other than the GM garbage. Also, heavier fluid 90w140 seemed to quiet mine down a bit.

As mentioned above, I have AMSOIL in it now...but I have thought about a heavier viscosity in the future.

justin311 · #5 (**permalink**) 07-13-09, 12:21 PM

Isn't Amsoil the best for that?

justin311 · #6 (**permalink**) 07-13-09, 12:21 PM

Whoops, you beat me to it.

justin311 · #7 (**permalink**) 07-13-09, 12:27 PM

I have the whine also. It is a brand new diff. I get it at 60mph. I'm going to try a different fluid also.

darkman · #8 (**permalink**) 07-13-09, 12:47 PM

Quote:

Originally Posted by Slithering_Joe

- Is this a normal thing with these diffs?
- Is this the signs of a dying diff?

The condition you describe is quite common, but it is not normal. IMO the differential should be changed. You can remove all doubt by simply pulling some of the fluid and sending it in for oil analysis. The degree of metal-related contaminates will indicate its condition.

Alan F · #9 (**permalink**) 07-13-09, 12:51 PM

WOW...this is almost down to the exact mileage of my original replacement and now I'm about to roll 33k and its whining again. Made the mistake of lowering my back seats when I put the bike in there and w/ the back seats down it sounds like a jet...and not the turbo spooling cool sound, but the whine magnafied.

If you are wondering if your diff whines...lower the back seat and drive around.

I'm taking mine in soon as my warranty also expires in Sept.

bigbadcj · #10 (**permalink**) 07-13-09, 01:41 PM

Thats normal is these cars. Ive never seen one that did not do it. Hell purchase a mclaren f1. Then you will really understand what gear whine sounds like...3rd will whine your ass out the car.

lollygagger8 · #11 (**permalink**) 07-13-09, 02:05 PM

Try the heavier fluid first.

You can always try dynomat....or ear plugs

Slithering_Joe · #12 (**permalink**) 07-13-09, 02:06 PM

Quote:

Originally Posted by bigbadcj

... Hell purchase a mclaren f1. Then you will really understand what gear whine sounds like...3rd will whine your ass out the car.

We're talking about a Cadillac differential not a McLaren transaxle. At one time the replacment diff was quiet and it was a relief. Now it is not. Just wondering if there is a time bomb below the trunk waiting to go off when I need the car the most.

OldRoadDawg · #13 (**permalink**) 07-13-09, 02:13 PM

Quote:

Originally Posted by bigbadcj

Thats normal is these cars.

I agree.
Mine has the 45 mph +/- whine under light throttle. Had it from day one and it's still there at 46K.
Had a base CTS before this. Identical whine. I've driven several CTS and SRX Cadillac.
Same whine in everyone of them.
I don't even hear it anymore until I try listening for it.
IMO much ado about nothing.

Alan F · #14 (**permalink**) 07-13-09, 02:47 PM

Quote:

Originally Posted by Slithering_Joe

We're talking about a Cadillac differential not a McLaren transaxle. At one time the replacment diff was quiet and it was a relief. Now it is not. Just wondering if there is a time bomb below the trunk waiting to go off when I need the car the most.

i respect the "that's the way it is" comments, but i'm not a "that's the way it is" guy, to my own detriment I know.

Like mine, it was dead silent for the first few thousand miles. I remember like yesterday when i had the cruise set on the interstate, had rear seat passengers, and the whine came back and stayed after no abuse whatsoever.

So...if its quiet for a few thousand miles...what changes? Not selling the V because of it but something most certainly happens that brings in the whine. After my next warranty trip I will probably use a better oil as well.

bigbadcj · #15 (**permalink**) 07-13-09, 07:56 PM

Quote:

Originally Posted by Slithering_Joe

We're talking about a Cadillac differential not a McLaren transaxle. At one time the replacment diff was quiet and it was a relief. Now it is not. Just wondering if there is a time bomb below the trunk waiting to go off when I need the car the most.

I know what the disscussion at hand is. Just saying it does it. Mine never blew and the stroker v i had never blew. I drive like a complete ******* too. Ive had my hands on a ton of these cars and they all make the same whine. If they all do it its normal. If you have one that does not, its not broke in or its not normal.