Hi everyone

Just joined up, I have a 2014/15 facelift model A7 3.0 tdi Quattro 272 ps. It has 40400 miles on the clock but its started making a noise while driving. It's like a whine/droning type of noise it starts as a low noise then increases in pitch as I go faster IT/s not a wheel bearing. I'm wondering if it could be the prop shaft center bearing. Has anyone came across anything like this? All help will be very much appreciated.

Hello Alan,

I’m not claiming this is the cause of your issue, but have  you taken the wheels off, and had the tyres thoroughly inspected for defects? Simple first-port-of-call elimination. 
Kind regards,

Gareth. 

Had each one off and used spare wheel and reversed them, noise coming from same place all the time. But thanks anyways. 

Alan

Thanks Alan,

Sorry to suggest what you have covered - always helps to state what has already been eliminated. 
When this noise gets to its maximum, have you tried accelerating and decelerating to see if the noise alters under these conditions?
Kind regards,

Gareth.  

Pitch increases the faster you go. My next step is to get it up in the air with the wheels of the ground to see if I can pinpoint it better. Thanks for your suggestions though, as I say any help at all.

Alan

Hi Alan, did you ever find out what the issue was? I’ve got the same issue. I’ve replaced my rear diff but still the same. 

A new differential is a drastic measure that is rarely needed. What other possible faults did you eliminate before then?

I took it Audi and the diagnosed a faulty rear diff. Then I took it to my local mechanic who said he didn’t trust Audi and done his own diagnostics and said it’s a faulty rear diff. Changed it last year most of the sound went away. A year later it’s back worse than ever. Took it to a new garage they diagnosed rear diff too. And changed it for another one. And the sound is still there. Now he’s saying he can’t pinpoint where the sound is coming from.

so 3 different mechanics diagnosed noisy rear diff. It’s now on its 3rd diff. And still whining. They said it’s not the rear wheel bearings. So at this moment it time I’m at a complete loss. Only thing is both diff jobs were mostly covered under my aftermarket warranty. So not really out of pocket more than a few £100. 

47 minutes ago, Bishop1 said:

so 3 different mechanics diagnosed noisy rear diff. It’s now on its 3rd diff. And still whining. 

I think it's safe to say the differential is not the problem, and that the mechanics you consulted are guessing.

I suggest you work methodically through the possible causes, eliminating each in turn, and hope to arrive at a definite or at least probable cause. Start with the tyres as mentioned by Magnet in 2022, then wheel bearings, rear tracking, CV or universal joints, prop shaft pillow bearing.

The tyres are the most likely culprit. Look for mis-matched tread patterns, wrong pressure, and balance.

14 minutes ago, cliffcoggin said:

I think it's safe to say the differential is not the problem, and that the mechanics you consulted are guessing.

I suggest you work methodically through the possible causes, eliminating each in turn, and hope to arrive at a definite or at least probable cause. Start with the tyres as mentioned by Magnet in 2022, then wheel bearings, rear tracking, CV or universal joints, prop shaft pillow bearing.

The tyres are the most likely culprit. Look for mis-matched tread patterns, wrong pressure, and balance.

Thanks for your reply. I’ll try and work through ur list. 
as for tyres. There Michelin PS4s all round with 5mm on the rears. Had an Audi service few months back there said tyres are fine. So I’ll check the rest of the list. 

1 hour ago, Bishop1 said:

 Had an Audi service few months back there said tyres are fine. So I’ll check the rest of the list. 

Would that be the same Audi centre that told you a new diff was needed? Why take their word for it when it is so easy to check for yourself.

No it was a different Audi main dealer

 I just got the car back, the noise is a lot quieter now and the sound now starts from bout 40mph+. Where as before you could hear it from 20mph. Going to take it to another Audi tech. He said he’s gonna go through everything and try and diagnosed the issue