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cts-v
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Discussion Starter #1
So I get this type of howl sound coming from the rear end every time I decelerate from 48 mph and then it goes away at 42 mph. Every now and then it'll happen when I decelerate from 10 mph and again goes away at 7 mph.

I've taken this to the dealer and service manager tells me this is normal with differentials because they rub on each other. I say it's not and could be a loose pinion bearing?

So I ask, is there any such thing as "normal" differential sounds?

Thanks in advance.
 

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2014 CTS Vsport Premium
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You can get a different sound when on the "coast" side of the gears vs the "drive" side, but it's not normally a problem.

There's a lot to setting up helical gears, it's not easy (been there done that). Are these factory, or did you re gear?

That said, cars this expensive should have quiet running gears.
 

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2011 CTS-V sedan, 69 Mustang Mach I
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No, that is not normal. My differential was making what sounded like road tire noise, they changed the differential and I hear nothing at all out of it now. I would have him show you a car on his lot that makes the same sound, if that’s what he thinks a differential sounds like. Or go to a different dealer.
 
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So I get this type of howl sound coming from the rear end every time I decelerate from 48 mph and then it goes away at 42 mph. Every now and then it'll happen when I decelerate from 10 mph and again goes away at 7 mph.

I've taken this to the dealer and service manager tells me this is normal with differentials because they rub on each other. I say it's not and could be a loose pinion bearing?

So I ask, is there any such thing as "normal" differential sounds?

Thanks in advance.
Good morning jduck,

I can understand how this noise from your back end would be concerning and I apologize for any frustration the lack of a resolution has caused you. It looks like you have already received some feedback from the forum, but I would be happy to add an additional layer of assistance if you plan on heading back to the dealership. If you are interested, please PM me and we can discuss the situation further.

Have a great day,

Austin J.
Cadillac Customer Care
 

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I had 3 diff's put in my 2011 before I traded it in. My current 2012 had a loud growl at startup when taking off and turning to the right. The current solution from GM now is changing the oil. Since then, no noise from the rear end that I can tell.
 

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2011 CTS-V sedan, 69 Mustang Mach I
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I had 3 diff's put in my 2011 before I traded it in. My current 2012 had a loud growl at startup when taking off and turning to the right. The current solution from GM now is changing the oil. Since then, no noise from the rear end that I can tell.
My Cadillac dealer didn’t change the fluid on mine before they replaced the differential, this was a couple weeks ago. However they did replace the drive shaft, and then a wheel bearing, before finally changing the differential, that cured the problem. I plan to put mine through a few heat cycles, and then replace the fluid at 500 to 1000 miles and hope the noise doesn’t come back.
 

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I had 3 diff's put in my 2011 before I traded it in. My current 2012 had a loud growl at startup when taking off and turning to the right. The current solution from GM now is changing the oil. Since then, no noise from the rear end that I can tell.
It may not have had the proper friction modifier from the get go. Or last change.
 

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'04V, '05V, '06SRT8, '10V, '13ZL1, '12 V, '16 Z06 SC757
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I changed my fluid out last weekend and used the friction modifier. About a quart came out (classic under fill) and about 1.5 qts went in. I had the howl under load but nothing while coasting. Never bothered me, just want to make sure it lasts a good long time. Less than $30 in parts and 30 minutes of your time. Great peace of mind.
 

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2009 CTS-V (TR-6060, Black Raven/Ebony, Recaros, Ultraview)
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I've had my differential fluid changed twice in 100,000 miles, and my differential has never been replaced. I don't think that an additive is used now. My only symptoms were a slight groaning when cold and turning in a parking lot.
 

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Gone; ‘09 V, ‘13 V coupe. Curr; ‘14 PG Vsport prem w/Kona interior
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^^If your dealership did the fluid changes for you, chances are the diff fluid they used had the friction modifier in it.
 

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cts-v
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Discussion Starter #11
Thanks for all the replies. They did say the fluid levels were to spec. Also, I believe GM's gear fluid now includes friction modifier without having to add something separately?

I've reached out to customer service in order to compare one of the dealer's models so we'll see what the next steps are...
 

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Gone; ‘09 V, ‘13 V coupe. Curr; ‘14 PG Vsport prem w/Kona interior
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Also, I believe GM's gear fluid now includes friction modifier without having to add something separately?
Correct. The dealership used Valvoline full synthetic gear oil, SAE 75W-90 with limited slip additive included on my V. I even took home 1 of the bottles with some of the unused fluid.
 

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Correct on the friction modifier or grape scent diff fluid. I use Mobil1 synthetic fluid so I needed to add it. For $30 I plan changing after every track day for good measure.
 

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I had the same howl on aggressive acceleration on my 2011 with 14k miles. Took it to the dealer about it end up replacing the supercharger and charged me $174 for a differential service. It still howls but much less than before. :rolleyes:
 

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Discussion Starter #18
I am on diff #4.....
How'd you get them to replace it the first time, let alone the third time? My instinct was to have the dealership replace mine under warranty, but the service manager kept singing about how it's all normal. What does he care as long they get paid by the warranty, right?
 

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How'd you get them to replace it the first time, let alone the third time? My instinct was to have the dealership replace mine under warranty, but the service manager kept singing about how it's all normal. What does he care as long they get paid by the warranty, right?
I have always wondered about the dealer not wanting to replace things. Is it a matter of the service not as profitable, meaning the job might tie up resources that can be used on more "profitable" service jobs?
 

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How'd you get them to replace it the first time, let alone the third time? My instinct was to have the dealership replace mine under warranty, but the service manager kept singing about how it's all normal. What does he care as long they get paid by the warranty, right?
Try another dealer.....
 
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