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Humming when Driving Above 30mph


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Hi All,

I'm looking for some help with my car (A4 2.0tdi B8 Auto Quattro 2014 SE), I recently changed the front wheel bearings (as a hub assembly) in October 2023.  Mid-December I noticed a humming/winding sound coming from the front right of the car when doing 30mph or above, which sounded very similar to wheel bearing noise (no clunking).  This would get faster/slower with wheel speed, and is constant (not influenced by acceleration or braking).  I checked the wheel bearings again, and they seem OK.  I checked the tyres and the front right looked out of shape - I was confident the noise was this tyre due to the uneven wear.  I got two new front tyres fitted and the alignment done, but the noise is very much still there.  Despite the alignment being done, the car is still pulling to the right.  I looked further and believe there is play in the front drive shaft inner CV.  I'm not too knowledgeable on quattro and the differentials etc but carried out a few more checks which were recommended by a mechanic.  I put the car on a lifter and put the car in drive to see if I could hear where the noise was coming from, as I couldn't spin them freely enough myself.  At first all wheels started spinning, but the front right was intermittent.  Soon only 3 were spinning (the front right wasn’t - so I couldn't listen for noise!).  I put the car in neutral and spun the front left wheel - the front right wheel did spin in the opposite direction as expected.  I then put the car back in drive but held the front left wheel still, the front right wheel didn't start spinning (I’m advised it should have at this point?).  I have been advised to try putting the car on a lifter, in drive, but turning the steering full lock to see if the front right wheel starts to turn.  I’ve also been advised to try disconnecting the prop shaft to the rear and see if the car drives to determine whether it’s a differential issue.  I have attached a link to a video of the play in the front right inner CV axle.  My query is whether from the above, and attached video, is it clear it's the CV axle, or could it be the differential?  If not, what further checks should I do to determine what the issue is?  I’m thinking it may be easier to take the car in to a garage having tried everything I can. 

Thanks in advance, RD.

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Hi Ryan 

1: have you jacked the car uo front end, and checked the wheels for play ? put your hands on the wheel at the 12 o'clock position and the 6 o'clock position push the top hand and pull the lower hand towards you is there any play . 

2: Does the CV , universal joints have grease in it ?

3: The vehicle pulls to the right  "Or pushed to the right ? "

4: The uneven tyre wear is significant. 

5: Is there traction in the wheel, Front right ? Jasonj



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Hi Jasonj, thanks for your quick response, I appreciate it!

  1. I have, there is no play in the wheels when pushed/pulled in the 12 and 6 o'clock positions. 
  2. There currently is no evidence of grease leakage on any of the CV joints - would it be safe to assume the grease is still there based on that? The outer CV on this particular wheel was replaced in September 2023.  
  3. I'm unsure what you mean by "pushed to the right" but when driving with the steering wheel straight, the car goes to the right (so I have to have the steering wheel turned slightly to the left in order for the car to go straight).  
  4. I understand the tyre was showing signs of cupping as the tread on the outside had worn patches every 6 inches or so around the circumference.  
  5. I'm not sure if there is traction in the front right.  How would I identify this?  From the testing I've done recently, I have a feeling it's free spinning and relying on the other wheels to propel the vehicle.  

Thanks, RD.

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Hi Ryan, Re

3: Pushed to the Right. This vehicle is all wheel drive . The symptoms you present would indicate that this wheel is indeed being Pushed by the Rear wheels, 60% .

Pulled forward by the Front wheels.  40% Front distribution under normal operating conditions . Distributed evenly in normal operating conditions. 

3a: If the front wheel does not have Traction ,  it is not under normal drive . This means in effect the rear wheels are Pushing the vehicle. The other front Wheel, Left side is Pulling the vehicle forward .  

4:The tyre on the suspected Wheel Right side has uneven wear on the outer circumference , with patching every 6 inches as the wheel is not sitting  square on the road surface . 

5: This would then put the wheel under undue load  along with the CV joints as these joints should be rotating under the propulsion from Drive shaft , and not freewheeling  and then develops the humming sound when the vehicle is under acceleration "extra load is applied" 

5a: Humming sound is created because of the frequency / pitch / resonance at speeds above 30mph .

5b: There is not audible sound at lower speeds , due to the lack of force being applied .  

6: Steering correction is an indication that you are having to compensate for a non operational front wheel , as you are having to use a left directional bias to maintain the vehicle in line . 

Synopsis: All those salient points mentioned by yourself would indeed point to this vehicle not having drive on this wheel . 

Prognosis: obtain OBD diagnostics . This will ascertain if you need: (ABS Sensor along with Drive Shaft , Differential) Jasonj




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Thanks JasonJ, appreciate your assistance and detailed response. 

Your response makes sense and I feel is quite an accurate representation.  

In relation to your suggested prognosis, please could you elaborate on how an OBD diagnostic would identify whether the drive shaft or differential is the issue?  I'm not aware of these being monitored, apologies if this is a daft question. 

I don't believe the output flange is spinning either during my above testing.  Could it be that there is an issue with the CV axle, but caused by a problem within the transmission/differential?

Would a worn output flange bearing cause enough play for the teeth not to bite?  Is my following understanding correct - the output flange for the side in question is linked directly to the ring gear, but the ring gear must be working for the front left wheel to be spinning?  Unless, as you say, the ABS sensor is faulty causing the wheel to apply the brake.  During the testing, when the wheel isn't spinning, I am able to turn it by hand so I don't believe the brake is activated. 

Having said that, it's jogged my memory and I forgot to mention earlier - I have had a few recent issues with the brake on this wheel.  Two to three instances, a scent of burning when getting out the car - the disk and hub is sizzling hot compared to the front left wheel.  Maybe you are correct that there is an issue with the ABS, but would this cause loss of drive from the transmission/differential or could it have damaged something within?

Thanks again, RD.

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Hi Ryan, Re

1: OBD plugged into diagnostics would identify what Differential  System is in this vehicle  eg ( Torsen with Helical gear  etc)

2:" Problem with CV axle".  It would appear that  CV Drive Shaft is  non  operational as it  is not driving the right front wheel. But has it has had Torsional forces ( That's the Twisting ones from being Pushed ) exerted onto it  Probably would be a consideration to look at it in greater detail for damage .. Due to the torsinal forces ..  but you dont mention grinding noises .

3: ABS sensor sends data to CAN bus ( Controller Area Network ) and then to ECU . Relays information about wheel spin etc As this Wheel is not Deploying ABS  ie flagging up as a warning on your dash making your brake pedal judder etc . Is Questionable Because in these circumstances it should :

3a: Maybe this is because this is 4 wheel drive the other 3 driving wheels  are compensating for this 

4 : The fact the Left wheel has no issues is a good sign " The fact you still got gears and a clutch" are all positive 

5: WARNING this vehicle will not handle as it should especially under heavy braking . 

6 : I am always reluctant to advise , due to the nature of this being an  open forum and other people may read it and  proceed to act on those instructions . But off the record . I would Take the CV drive shaft out 

7: Take it to a garage "For a Quote" as they are conversant with this  and will advise you what needs to be done,   BUT it really does need addressing  Jasonj

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Hi JasonJ,

Thank you, I will see if I can get OBD looked at this week.

I will get in touch with a local Audi specialist and request a quotation - rather than take the drive shaft out and investigate further, I imagine they will advise if the CV drive shaft is faulty when carrying out their diagnostics.  

Thanks, RD

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