Rear diff noise...

[knight001]

Hi all....

So just had the 24,000km service and was able to duck away to Wagga Wagga for the Easter break.

So now that I’m back I have noticed a noise coming from the rear when I’m driving and turning right majority of the time.

Also if I’m feathering the accelerator pedal or reversing low speed.

I’m booked in tomorrow for it to be checked and hoping it’s not a major deal. Also hopefully the dealer will hear it as it seems to be the loudest on cold starts....

Anyone had this issue or had it fixed? Any advice or details I can share with dealer would be appreciated.

2019 ZB Commodore VXR.
Cheers... Tim

 

[Skylarking]

My experiance is that dealer service personel are clinically tone deaf cause they can never hear noises that are obvious to everyone else

You'll need be able to tell them what speed the noise coming from the rear occurs at and whether on acceleration, coasting or steady throttle. Also you'll ned to describe the noise and whether its a whine, rumble, etc. Best to read the relevant sections in the VF or ZB workshop manual (links in some threads on these forums) just to familiarise yourself with their terminology.

How many kms has the car done prior to the trip and is this the first time you've driven the car for 4 hours straight?

 

[stooge]

Hi all....

So just had the 24,000km service and was able to duck away to Wagga Wagga for the Easter break.

So now that I’m back I have noticed a noise coming from the rear when I’m driving and turning right majority of the time.

Also if I’m feathering the accelerator pedal or reversing low speed.

I’m booked in tomorrow for it to be checked and hoping it’s not a major deal. Also hopefully the dealer will hear it as it seems to be the loudest on cold starts....

Anyone had this issue or had it fixed? Any advice or details I can share with dealer would be appreciated.

2019 ZB Commodore VXR.
Cheers... Tim

check out this forum

AWD Makes Noise Near Rear of Car when Turning at Slow Speeds

I've noticed a weird noise coming from what sounds like the AWD system when turning at slow speeds. The noise sounds hollow and kind of like a grumble/moan that comes from the rear of the car and seems worse during cold starts. Has anyone else noticed this? I'm trying to understand if this is...

buickforums.com

it is the same vehicle but sold in the us

 

[Skylarking]

check out this forum

AWD Makes Noise Near Rear of Car when Turning at Slow Speeds

I've noticed a weird noise coming from what sounds like the AWD system when turning at slow speeds. The noise sounds hollow and kind of like a grumble/moan that comes from the rear of the car and seems worse during cold starts. Has anyone else noticed this? I'm trying to understand if this is...

buickforums.com

it is the same vehicle but sold in the us

Interesting read.

Me, I've got no idea what the service life is for a twinster drive system which uses slipping clutch packs to provide drive to the wheels. These slipping cluth packs are used to send varying amounts of torque to help stear the car around corners. It's like brake vectoring on the HSV's and LE commodores but doesnt waste energy by applying brakes.

When driving straight ahead the twinster clutch packs should be fully locked so will not suffer any wear. During turns, the brains will command varying amounts of slip to one axle which will by design generate heat and wear of the clutch packs... Problem is how much slip and how often is such commanded with what rates of wear? Do these twinsters have any oil coolers?

As is, GM's reputation with their LSD's are that the clutch packs are a known weakness and they fail. But such LSD failures only result in an open diff so it's not catastrophic. With these twinster diffs, when the clutch packs fail, i'd assume you'd loose drive to one side and soon after to the other side. In such cases you'd have a loss of rear drive... Guess it's good teh ZB has AWD (but isn't the centre diff also based on clutch packs )

Great design, probably let down by not using metal plate wet clutches which supposedly last longer... Lack of diff oil cooling (if thats the case) probably also doesnt help

 

[Jack GS]

There have been a lot Regals going through rear differentials. It sounds like you have some of the same symptoms described by the Regal owners, so be prepared to have the entire differential assembly replaced. Check out this thread for more details:

Joining the Rear Diff Club

 

[Anthony121]

I know of the SA Police went through a few of these Twinster Diffs in 2019. The V6 has too much power to drive the diff Unable to source parts resulted in VOR's

 

[Jack GS]

I know of the SA Police went through a few of these Twinster Diffs in 2019.

Interesting... do you have more info on that?

Unfortunately, from what has been shared on the Buick forum, the issue is not limited to the V6. There have been about a half dozen folks with the I4 speak up and only one with a V6. That's not statistically significant given there are far fewer V6s in the States. Only the GS trim has the V6, and all other trims have the 2.0T I4.

I haven't had any issues yet. I drive it hard but I'm sure I don't come close to what the Police put them through. Time will tell. I guess I better break it before warranty is up... Knowing this was a potential issue early on, I had ALL fluids in the car replaced at 1,000 miles. Dealer said everything looked good then, FWIW.

 

[knight001]

Well reporting back after service visit today.

When I dropped the car they asked me to wait for the Holden Foreman to go for a drive with me. He noticed the sound straight away.

He showed me from what I could work out was a tech line report which advised to change the gear oil.

He said that the oil is hard to find at the moment as it’s expensive and replaces the standard oil in the diff.

Picked it up this arvo and seems good as new. I will test things out over the weekend to ensure it’s sorted...

 

[knight001]

So update...

Feels a lot better to drive however at low speed and entering a mild incline the car feels sluggish and I feel the need to put my foot down to go back a gear.

I know that this could be related to the factory tune in the transmission as I have read about this elsewhere in car reviews where it was noted that while it is a good transmission it can be sometimes be lazy to kick back at low speed and small inclines.

I guess that I did not notice it as much before and wonder if the diff issues which seem fixed with the oil change had anything to do with it?

Maybe the transmission needs resetting? (Not sure how to do that) or could something else be acting up? Or perhaps a better transmission tune is in order...

Other than that... It’s a dream to drive!

 

[Skylarking]

Changing diff oils doesn’t change the diff ratio so changing oils won’t impact on the logic used by the auto...

It just may be the “smart“ auto has learnt your driving behaviour over the last few tanks which may have been a little subliminally influenced by your right foot due to the diff noise. Alternatively, it could just be your imagination playing with you as you look and listen for differences after the oil change.

In any case, these smart autos learn and adjust for wearing clutches which is great. Supposedly they also learn driver behaviour which can make them feel porky and slow if you drive like nan for too long... I believe it’s called adaptive transmission and such learnings can be reset but the process would be gearbox specific. Supposedly it isn’t complex to do a reset though you probably need ODB test equipment to do it (=Holden).

The reset process is gearbox specific and I don’t know what gearbox is in the ZB other than there are 2 types. Just for giggles, here’s one reset/relearn process... for a GM 8 speed gearbox which is probably not your gearbox as I think petrol ZB’s have 9. Speeds...