Grinding noise from rear - 2015 S4

[SteveYem]

There is a road I take every day home from work that has a sweeping right-hand turn that I go through at 40-45 mph. Lately I've been hearing a metallic grinding/rubbing sound coming from the rear...maybe rear driver side but hard to tell....as I am going through this right-hand sweeper. The sound occurs roughly 2x per second, so it doesn't seem frequent enough to be a brake rotor rubbing sound (my old WRX used to have rear rotors that would rub on the dust shields).

The car is a 2015 6MT with sport differential. I can't help but think (fear?) that this sound is coming from the sport diff. I only hear it when I am into this long right-hand turn, during which the sport diff would be 'working'. I never hear it when going straight, nor do I hear it when going through shorter duration turns. It's like it takes a couple seconds of being steady into the turn until I hear it.

I am going to keep an ear open for it tomorrow when going through the same turn on the way to work (sweeping left-hander). Has anyone else experienced this? Any recommendations? Something tells me this is going to be difficult to replicate for the service tech.

For reference, all modifications are listed in my signature, although I'm not sure any of them would make a difference.

[sergzz]

There is a road I take every day home from work that has a sweeping right-hand turn that I go through at 40-45 mph. Lately I've been hearing a metallic grinding/rubbing sound coming from the rear...maybe rear driver side but hard to tell....as I am going through this right-hand sweeper. The sound occurs roughly 2x per second, so it doesn't seem frequent enough to be a brake rotor rubbing sound (my old WRX used to have rear rotors that would rub on the dust shields).

The car is a 2015 6MT with sport differential. I can't help but think (fear?) that this sound is coming from the sport diff. I only hear it when I am into this long right-hand turn, during which the sport diff would be 'working'. I never hear it when going straight, nor do I hear it when going through shorter duration turns. It's like it takes a couple seconds of being steady into the turn until I hear it.

I am going to keep an ear open for it tomorrow when going through the same turn on the way to work (sweeping left-hander). Has anyone else experienced this? Any recommendations? Something tells me this is going to be difficult to replicate for the service tech.

For reference, all modifications are listed in my signature, although I'm not sure any of them would make a difference.

Sounds like it could be the diff based of your description. I would really make sure. Since the sport diff is more effective on power, try going into the corner slower and accelerate out sooner. If it's the diff you should be able to hear it more this way.

And yes replicating to the dealer is key. If you can't do it with them then they will just tell you that everything is perfectly fine.

Are you planning on modding the car?


Sent from my iPhone using Tapatalk

[SteveYem]

Sounds like it could be the diff based of your description. I would really make sure. Since the sport diff is more effective on power, try going into the corner slower and accelerate out sooner. If it's the diff you should be able to hear it more this way.

And yes replicating to the dealer is key. If you can't do it with them then they will just tell you that everything is perfectly fine.

Are you planning on modding the car?


Sent from my iPhone using Tapatalk

Thank you for the advice. I will give that a try on my way home today.
The car is "lightly" modified. No engine modifications, but lowered on coilovers, cat-back exhaust, currently on aftermarket winter wheels and tires, 034 transmission mount. Nothing that seems like it would affect the function of the differential, though.

[bhvrdr]

The fact that it is happening on the sweeping right hand turn makes me think a bad wheel bearing. The other thing is that you could be rubbing on something like an end link or tire to fender liner etc. Look for any contact marks. Does it sound like a humming/groaning noise or like a rubbing noise?

Mike

[SteveYem]

The fact that it is happening on the sweeping right hand turn makes me think a bad wheel bearing. The other thing is that you could be rubbing on something like an end link or tire to fender liner etc. Look for any contact marks. Does it sound like a humming/groaning noise or like a rubbing noise?

Mike

Thanks for your input. The sound is like two ceramic plates rubbing together. I do have aftermarket rear sway bar and solid endlinks, but I should note that I've had those installed for ~4 months on this car and for ~1.5 years on my old B8 and never noticed an issue before.

[bhvrdr]

Thanks for your input. The sound is like two ceramic plates rubbing together. I do have aftermarket rear sway bar and solid endlinks, but I should note that I've had those installed for ~4 months on this car and for ~1.5 years on my old B8 and never noticed an issue before.

That sounds more like rubbing. Stuff shifts all the time. It can happen. Bolts can loosen up, springs can settle, bushings can wear, exhausts contract and expand. The bearing would be a groaning noise. Here is a good video...

https://www.youtube.com/watch?v=46F07Qx0EoI

Mike

[SteveYem]

That sounds more like rubbing. Stuff shifts all the time. It can happen. Bolts can loosen up, springs can settle, bushings can wear, exhausts contract and expand. The bearing would be a groaning noise. Here is a good video...

https://www.youtube.com/watch?v=46F07Qx0EoI

Mike

Thanks for the link. This is definitely not that sound. What I am hearing is a muted and less continuous version of a brake rotor rubbing against the dust shield. What led me to thinking it is the sport diff is that I know it's a wet multi-plate clutch arrangement and I could understand if it would make noise if the mating plates are not adequately lubricated. Maybe if the fluid level in the differential is too low the mechanism can run a bit dry with the car in a corner and result in this noise. I really don't know, just speculating at this point.

[MVR 155]

Steve..... I think I would pull a wheel and closely check the rotor to dust shield potential for contact. By your description that is exactly what it sounds like it could be. I doubt the diff would be such a pronounced/precise sound (given your description that it sounds like ceramic plates rubbing together...... that is pretty detailed), given that it's contained in the housing it likely would be pretty muffled. Also if the diff was making that kind of noise it would very possibly be accompanied by a shuddering/vibration. Best of luck in sorting it out...... stuff like this can be such a pain in the ass to track down.

[SteveYem]

Steve..... I think I would pull a wheel and closely check the rotor to dust shield potential for contact. By your description that is exactly what it sounds like it could be. I doubt the diff would be such a pronounced/precise sound (given your description that it sounds like ceramic plates rubbing together...... that is pretty detailed), given that it's contained in the housing it likely would be pretty muffled. Also if the diff was making that kind of noise it would very possibly be accompanied by a shuddering/vibration. Best of luck in sorting it out...... stuff like this can be such a pain in the ass to track down.

Thanks for your input. I will be swapping my summer wheels/tires on hopefully this coming weekend so I will check the clearance at that point. The only thing that makes me think it's not the brake disc rubbing is that it's not a continuous sound... it's maybe 2x per second. At 45 mph land speed (which is about what I am driving when I hear it) and assuming the theoretical outer diameter of my 245/40/18 tires as 25.72", my wheel+tire+brake disc rotates at approx. 9.8 revolutions per second, so it would seem weird that I would only hear this sound once every ~4.9 revolutions. I'm not saying that makes any sense for the sport diff either, but I think it makes less sense for a wheel/tire/rotor rubbing issue.

In any case I will also check for signs of rubbing when I have the wheel off this weekend.

[RainJer]

Has your car been to a dance club recently?

[SteveYem]

Has your car been to a dance club recently?

Ha....no. There's a joke in here somewhere. Something to do with BPM?

[MVR 155]

Thanks for your input. I will be swapping my summer wheels/tires on hopefully this coming weekend so I will check the clearance at that point. The only thing that makes me think it's not the brake disc rubbing is that it's not a continuous sound... it's maybe 2x per second. At 45 mph land speed (which is about what I am driving when I hear it) and assuming the theoretical outer diameter of my 245/40/18 tires as 25.72", my wheel+tire+brake disc rotates at approx. 9.8 revolutions per second, so it would seem weird that I would only hear this sound once every ~4.9 revolutions. I'm not saying that makes any sense for the sport diff either, but I think it makes less sense for a wheel/tire/rotor rubbing issue.

In any case I will also check for signs of rubbing when I have the wheel off this weekend.

If it's super close on clearance it may take loading the car in the turn and then small bumps which cause just enough added deflection to cause it to scrape momentarily. Again..... It's just my guess and hopefully it's something this simple to correct. Best of luck on the diagnosis this weekend!!!!!

[switchedstance]

Actually just heard the same noise on my '15 today making a 90* turn out of my office parking lot. Noticed it yesterday but thought it was just my tire slipping on some sand. Today with radio off, defiantly heard it from the rear area, sounds like a very light traction control or abs intervention noise. I also get a lot more diff whine than in my previous non-sport diff a5, especially when coasting in gear, when the revs drop below 2500. Depress clutch, whine goes away. Not gunna love sleep over it, sure its part of the normal operation. Worst case, that is what warranty is for.

[vacsimile]

Also check your driveshaft for any wear marks. The exhaust could be shifting and rubbing against it.

[B8Addict]

Sorry to bump this thread after so long but I noticed my vehicle is doing the same thing.. not reproducible for shorter duration turns. Was there any resolution to this?

Ray

[vwblackb5]

This has now happened to me. I thought it was just the metallic brake pads when cold, but today I heard it again. It sounds like metal to metal grinding, then becomes high pitch then more grinding. Sound does not seem like it's affected by steering wheel feedback or braking. I think the rear rotor/brake shield is rubbing. Not sure why all of a sudden but I'm taking it to the dealer to have a look.

Car just reached 1200 miles today and here I go to the dealership ...

[SteveYem]

Sorry to bump this thread after so long but I noticed my vehicle is doing the same thing.. not reproducible for shorter duration turns. Was there any resolution to this?

Ray

Sorry that I completely missed your post! Yes, there was resolution. It turned out to be that the wheel well liner to the rear of the wheel had been somehow pushed out so that it would contact the tire under certain conditions. I originally posted that it sounded like a metallic sound, specifically similar to my old WRX with aftermarket rear brake rotors which would rub on a small section of the dust shield. But anyway, when I got into it on the S4 I saw the wheel well liner deformed (pushed in toward the rear of the tire), as well as being worn thin with a small hole worn through it from rubbing on the tire.

This has now happened to me. I thought it was just the metallic brake pads when cold, but today I heard it again. It sounds like metal to metal grinding, then becomes high pitch then more grinding. Sound does not seem like it's affected by steering wheel feedback or braking. I think the rear rotor/brake shield is rubbing. Not sure why all of a sudden but I'm taking it to the dealer to have a look.

Car just reached 1200 miles today and here I go to the dealership ...

Your sounds different than mine. My guess would be a stone or some other foreign object caught between the brake rotor and dust shield.