Droning noise from D4 4.2tdi
 

Hi all,

Have a D4 4.2tdi that I bought 2 1/2 years ago with 27k. It's now got 57k miles.

Yesterday it started making a noticeable droning / humming noise, difficult to tell where it comes from but gets worse with road speed. It's worst at about 70 going down to 50 with engine braking.

On a trip to Southampton today the sports differential warning light (yellow) came on but has now gone again. Took it to a dealer who cleared the warning, took it for a test drive and said they could not find anything wrong. Noise is still there though. Definitely not tyres as new ones fitted very recently.

Any thoughts on how to proceed - just brace myself and go back to the dealer to investigate the noise? Is it likely to be anything other than the diff?

Cheers

If you have a noise like that along with a warning about the diff I would looking at that further, even if you have to get creative and secure a go pro wrapped in foam and tied onto the diff just to see if you can get a recording from it.

Is the car still in warranty? if it is i would push the issues before it expires.

Had a drone on my D3, same drive train, was a rear wheel bearing.

Never any warning lights though, I'd doubt the diff warning light was a coincidence!?

Yep id agree - had a rear wheel bearing go on a D3 which gave a similar droning noise, it just got louder gradually until we changed it. +++

You say you had new tyres? Front or rear or all 4?

I also think the diff is most likely given the noise has just started suddenly. A wheel bearing wil gradually get nosier unless the bearings suddenly collapse.
I have similar miles on a D4 3.0TDI without any issues but i dont have the sports diff. My previous D3 had one rear wheel bearing replaced after a similar droning noise but it was at about 150k miles.
If you are out of warranty, it would be worth having the diff oil changed, condition of the old oil might indicate if the diff is in trouble. Shouldnt cost much to have it done.

Take that with a very large pinch of salt. I had an alleged Audi "Master Tech" tell me that he "had no idea what was wrong with my EPB" and to "exercise it a few times and give it a couple of days to settle back down" when all it needed was the basic "place in park and turn ignition off with handbrake off" calibration and it was fixed. :tuttut:

If the diff light came on and it was making that much noise, get it to someone who will give you a better diagnosis other than "dunno mate.. seems alright to me"... :mad:

The bearing on my D3 started groaning clear as day one day, parked it up after a 200 mile drive, no noise - came back a few hours later to drive home, groaned all the way home. Was like that for a few 1000 miles until I isolated which bearing and got it booked in, my initial worry was the diff!

That said, oil change won't hurt and may as you say tell a story!

Hi all,

Great answers - thanks very much. Sounds like the way forward is to ask for some help in changing the diff oil and in isolating whether there is a wheel bearing issue. Trip to the local indy will be booked today.
It is out of warranty (by 6 months grrrrr) and had all 4 tyres changed and tracking done. The noise was evident before and after the tyre change.

Does anyone happen to know what would trigger the sports diff system warning? No idea what sensors feed into it - maybe the abs sensors?

Cheers

I'd say the first step would be to get a mechanic in the back of you car to listen to the noise, just spinning the wheel on mine on the ramp didn't trigger any noise, had to be under load and at motorway speeds.

Ended up with a tech crawling all over the back seat on the M60 for him to work out which side it was, apparently the sound deadening doesn't help. He said that the main dealers use a microphone setup clipped to various points on the suspension to isolate, his method proved to work also +++

The noise you describe sounds like a bearing but I can't see why it would bring a diff light on , does the d4 have some kind of active diff with limited slip control .
If you turn on a tight lock does it have any sort of binding feel to it

I think it has hydraulic controlled sports diff, they do suffer from high pressure sensor faults, electric and software problems on different Audi models.

Considering you have droning noise it could be wheel bearing worn letting the hub to move around a bit and affecting ABS sensor readings and that confuses diff control. But I would expect it to bring up ESP and/or ABS lights as well. Check the wheel bearings, log ABS sensor readings while driving and check the fault codes.

Hi all,

Thanks again for the replies. Quick update:
The droning noise was a wheel bearing, replaced and noise issue is solved. Cost approx £300 at the local indi for reference.

Did not fix the sports diff light though, coincidental. That turned out to be 2 sensors (temp and oil level) and 2 of the clutch / fluid valves controlling the hydraulics in the sports diff. That was sorted out at the dealer - shade over £800 (ouch).

Master tech confirmed that the main cause of the light coming on is electronics / generally sensor problems. From the research I did this seems to be fairly common across sports diff on A4s.

Cheers

Glad it's sorted.

But one thing worth remembering here the "master tech" confirmed it is the electronics making the light come on but also couldn't find anything wrong with it to start with. I'm not an electrician or a "master" tech even i know it electrics that make a light work.