Diff Whine ... Common?
Thread Starter
Racer
Joined: Mar 2019
Posts: 355
Likes: 169
Diff Whine ... Common?
I’ve started to notice some diff gear whine in my ‘22 HTC. 700 miles. There’s a noticeable whine in the 65-70 mph range, regardless of gear. So I’m wondering if others have noticed it and if you’ve addressed it with GM? I’m probably more interested in hearing from those that don’t have an issue since I’m anticipating the “they all do that “ response. The local service Mgr has driven mine and stated ‘he wouldn’t be happy if it was his car’ ... so I hope he will go to bat for me. I made a similar post on the ‘general’ forum but didn’t get much useful info. I hope this group is more helpful.
Pro
Joined: Feb 2007
Posts: 697
Likes: 663
From: Portage Michigan
Tremac DCT
Above is a link to a very good article regarding the development of the C8, as well as the transaxle. One very important detail is that they wanted a common fluid to lubricate the gears, clutches and everything else. To accomplish that they had to do away with a hypoid ring and pinion, since it in itself requires a very special fluid that is not compatible with the other things now in there. So, the ring and pinion gear set is an on-center alignment. Hypoid gearing was developed decades ago to reduce gear whine. So, it is inevitable that there is a very faint whine from the rear. It is normal, and almost expected, but I doubt Chevy would ever say that. Being the mechanical guy that I am, I like the sound of a flat tappet solid cam, supercharger whine and turbo spool-up, so a whine of a rear gear from a fantastic sports car is not objectionable to me.
The whine you are hearing is considered normal. Enjoy the ride.
Above is a link to a very good article regarding the development of the C8, as well as the transaxle. One very important detail is that they wanted a common fluid to lubricate the gears, clutches and everything else. To accomplish that they had to do away with a hypoid ring and pinion, since it in itself requires a very special fluid that is not compatible with the other things now in there. So, the ring and pinion gear set is an on-center alignment. Hypoid gearing was developed decades ago to reduce gear whine. So, it is inevitable that there is a very faint whine from the rear. It is normal, and almost expected, but I doubt Chevy would ever say that. Being the mechanical guy that I am, I like the sound of a flat tappet solid cam, supercharger whine and turbo spool-up, so a whine of a rear gear from a fantastic sports car is not objectionable to me.
The whine you are hearing is considered normal. Enjoy the ride.
Thread Starter
Racer
Joined: Mar 2019
Posts: 355
Likes: 169
Tremac DCT
Above is a link to a very good article regarding the development of the C8, as well as the transaxle. One very important detail is that they wanted a common fluid to lubricate the gears, clutches and everything else. To accomplish that they had to do away with a hypoid ring and pinion, since it in itself requires a very special fluid that is not compatible with the other things now in there. So, the ring and pinion gear set is an on-center alignment. Hypoid gearing was developed decades ago to reduce gear whine. So, it is inevitable that there is a very faint whine from the rear. It is normal, and almost expected, but I doubt Chevy would ever say that. Being the mechanical guy that I am, I like the sound of a flat tappet solid cam, supercharger whine and turbo spool-up, so a whine of a rear gear from a fantastic sports car is not objectionable to me.
The whine you are hearing is considered normal. Enjoy the ride.
Above is a link to a very good article regarding the development of the C8, as well as the transaxle. One very important detail is that they wanted a common fluid to lubricate the gears, clutches and everything else. To accomplish that they had to do away with a hypoid ring and pinion, since it in itself requires a very special fluid that is not compatible with the other things now in there. So, the ring and pinion gear set is an on-center alignment. Hypoid gearing was developed decades ago to reduce gear whine. So, it is inevitable that there is a very faint whine from the rear. It is normal, and almost expected, but I doubt Chevy would ever say that. Being the mechanical guy that I am, I like the sound of a flat tappet solid cam, supercharger whine and turbo spool-up, so a whine of a rear gear from a fantastic sports car is not objectionable to me.
The whine you are hearing is considered normal. Enjoy the ride.
I haven’t read the article yet, but using a common trans fluid does not preclude using a low-noise differential gear set. Many modern transmissions have a common lube and are quiet. I worked In tractor DT development for many years. Our trans used wet clutches and brakes ...not unlike the DCT. It used a common fluid and was the reservoir for the entire hydraulic system. We used on-centerline (spiral/bevel) ring & pinion and they were quiet. IMO, DCT whine probably has more to do with contact ratio, overall gear dimensional quality, and setup. TheC8 is not a big block C2 or C5 with an aftermarket blower. Gear whine is like finger nails on a chalkboard to me and it shouldn’t be a characteristic of a car of this caliber. I’ll be addressing it with GM so will try to update this post with developments.
Last edited by Thera p; Nov 30, 2021 at 09:09 AM.
Melting Slicks
Joined: Nov 2012
Posts: 3,161
Likes: 686
From: SUFFIELD CONNECTICUT
Yes , I have rear gear whine between 50 and 60 mph on light throttle or maintaining speed on level ground, with just a little off throttle from 60 to 55 mph. I have a 2021 , 2600 miles, non Z51.
Last edited by BJ67; Dec 6, 2021 at 07:58 PM.
Thread Starter
Racer
Joined: Mar 2019
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Melting Slicks
Joined: Nov 2012
Posts: 3,161
Likes: 686
From: SUFFIELD CONNECTICUT
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Thread Starter
Racer
Joined: Mar 2019
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I’ve heard (on FB) of one instance of the owner adding an additional 2 qts of fluid to the transmission (as recommended for track use) and it reduced diff whine. Can anyone confirm whether an oil ‘add’ does reduce whine?
Thread Starter
Racer
Joined: Mar 2019
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Race Director
Joined: Aug 2016
Posts: 12,710
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From: Garden Valley CA
Mine slightly whines at higher speeds at part throttle when it has warmed up. It is most obvious when I hold the throttle in a neutral load situation. Like going down a very slight grade or letting the car slightly decelerate.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
Thread Starter
Racer
Joined: Mar 2019
Posts: 355
Likes: 169
Mine slightly whines at higher speeds at part throttle when it has warmed up. It is most obvious when I hold the throttle in a neutral load situation. Like going down a very slight grade or letting the car slightly decelerate.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
For those that don’t think they have an issue, please listen closely at highway speeds. I’d love the hear from owners that have NO gear whine to support my discussions with GM.
Thx to all for your input!
Thread Starter
Racer
Joined: Mar 2019
Posts: 355
Likes: 169
Mine slightly whines at higher speeds at part throttle when it has warmed up. It is most obvious when I hold the throttle in a neutral load situation. Like going down a very slight grade or letting the car slightly decelerate.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
I noted it on my service order when I brought the car in for its first service. The response was "no abnormal noise heard at this time".
The DCT transfer spur gears have straight cut teeth vs helical teeth which are quieter. I suspect a slight whine is inherent in the design.
Race Director
Joined: Aug 2016
Posts: 12,710
Likes: 10,140
From: Garden Valley CA
Race Director
Joined: Aug 2019
Posts: 12,351
Likes: 14,181
From: Central Illinois
They all whine a little at steady state cruise in the 60-70 mph range. Mine has never changed in 4,400 miles and so it's just characteristic of the design. I live with it and it's fine.
Thread Starter
Racer
Joined: Mar 2019
Posts: 355
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I had the dealer add an additional 2 quarts to the tranny as recommended for track use. It seems to have reduced the whine a little bit. I might try add some insulation to get the noise down to a level is not objectionable to me. Not sure what to use or where to apply so need to do some research.