Whining/Whirring Noise On Overrun
 

Just noticed this over the last week or two. It has definitely got worse/louder but seems to have settled now. It can be described as a whirring or whining noise coming from the gearbox tunnel area in the front of the car, say under the MMI screen to driver's foot-well area. A bit like electrical interference noise you used to get when your alternator wasn't suppressed in the old days (for those who remember).

• It doesn't do it on acceleration or whilst cruising.
• It only does it when foot comes off the gas and decelerating.
• It does it in every forward gear and is road speed linked and NOT engine speed linked.
• It stops if you select neutral while slowing down.
• Selecting 'Sport', 'Tip' or 'Drive' makes no difference.
• I have slightly uneven wear levels on tyres front to back (2mm rears & 5 mm fronts).
• Gearbox was flushed/serviced a year ago.
• I have also noticed a slipping/spinning/shuddering from the rear tyres when going really slow and on a tight-ish lock (not sure if this is connected).
• No vibrations, clunking, grinding or any other nefarious noises from anywhere.
• Car drives smoothly and as usual from stationary to 3 digit figures. Performance doesn't seem effected.
• Noise seems to abate at around 10mph when slowing down.
• Above 80-85 it seems to pulse/drone when decelerating until about 70 when it becomes a constant whine.
• Car has done 78,000 miles
• No oil/fluid leaks from anywhere or smells of burning oil.
• Had the transfer box off and new gasket and gear oil last year at same time as gearbox service.
• Yet to check VCDS for any codes. Will update.

Is this gearbox, diff, bearings, cv joints? I think it may be gearbox as it goes completely when in neutral. What do folk think?

I'd start with looking at the carrier bearings/mounts on the main driveshafts.
What mileage are you at ?
You probably need to get the car on a lift & get someone to run the car through the gears with the road wheels off the ground to try & identify it.
I had something similar on a D3 but the noise seemed to come from under the rear seat, making me suspicious of the rear diff. It turned out to be a rear wheel bearing at 140K miles approx. From memory, the noise got louder with road speed which would make sense.

Hi Joe. Sorry, yes. Updated OP with new bullet points. 78k. Agree. Need to get someone to look at it before something goes pop. Its not looking very promising if the noise goes completely when in neutral is it? Surely that means all of the drive-train (diffs, CVs, transfer box, prop shaft, wheel bearings, etc) is all still moving and all I have done is remove the gearbox/TC from the equation?

On a deceleration run the and gearbox in normal operation it would allow some degree of engine braking by delivering torque to the engine would it not?

If my understanding stands true then extra load would be applied to all the other components as against to a in neutral test.

When it stops at around 10 mph, check your driver info display to see if that matches the time the gearbox is shifting down to 1st.

Very good point Del, yes you're correct, so it could still be something like a dodgy CV joint (he says hopefully...) :(

I will check that Tony, yes, but I think it doesn't shift down to 1st until really low, like 5 mph or something, maybe even lower. I will try it tomorrow to see. I have done about 180 miles in it over the weekend and to be honest it doesn't seem to be getting any worse. Looking back, it seemed to have started around the time of that really really hot weather, when it was about 28-30 degrees for a couple of days. Maybe coincidental. It's just been in for a longlife service and a couple of other odd jobs to Audi and they didn't comment, so we will see. Thanks all.

It's still in 3rd (sometimes 2nd) when slowing down to 10 mph and only really drops into 1st if speed is like 2 or 3 mph or I stop. So 10 mph is not really related to a specific gear.

The behaviour sounds like the prop centre bearing, but the mileage is very low for that to be happening.

Did you ever get to the bottom of it?