Quiet whining noise

[mannyo]

Not having much luck with the D3.

I had the exhaust leaks fixed last week, so now the car is silent when driving along, but now have a couple of sounds which were obscured by the loud exhaust.

Once the car warms up when driving at 70mph there is a noticeable whine coming from somewhere, This whine is stops if pull into the services on the motorway for say 1/2 hour, but will return a short while later.

Also when coming to stop with a small amount of steering input there appears to be a slight judder just as the car comes to a stop. There is no problem when travelling in a straight line.

Now I have alarm bells ringing, thinking Diff or Transfer box problems. If I shift to N on the motorway the sound remains but seems to get quieter. At 60mph you dont really here it, and at 80mph its not noticeable either.

All four tyres currently have different tread levels, so once the D2 is sold they will all be replaced. Not sure if this is the cause but there will be rotational speed differences across all four corners.

[mannyo]

This weekend the car has been driven quiet a few miles,

Blandford to Cambridge, then Cambridge to Bury St. Edmunds via Elveden, Then Bury St. Edmunds back to Cambridge, Cambridge to Stevenage, Stevenage to Blandford.

Listening as much as I can, I have not worked out where the sound is coming from apart from it appears to be from behind me, I cannot be 100% sure though.

Observations.

At 60mph the sound is still there, but the frequency is lower than 70mph.
At 75mph the sound is still present but higher frequency.
The sound varies with road speed, and not engine RPM. Shifting down manually the sound does not change.
Lifting off the throttle, the sound returns after a short period even whilst slowing down.
If when driving you ease of so the car is neither slowing down or speeding up the sound goes much quieter.
If you floor it the sound goes away until a steady speed is obtained.

First port of call is going to be replace tyres I think, then the diff oil perhaps if the tyres don't fix it. I dont think its a wheel bearing, although again cannot be 100%. Even after driving 100 miles, I checked the wheel temperatures at Winchester services and all 4 wheels where stone cold so its not brakes either.

[snapdragon]

Originally Posted by mannyo

Even after driving 100 miles, I checked the wheel temperatures at Winchester services and all 4 wheels where stone cold so its not brakes either.

You may as well change the diff oil. The rear is easy and the front is a little harder as it requires an oil extractor as there is no drain.
I used FUCHS Fuchs Titan Sintopoid 75W-90 Axle/Diff Fluid from Opie Oils as it meets the VAG spec. ELSAWIN workshop manuals are available from ebay, TPB etc...

[mannyo]

This juddering sound is starting to bug me somewhat. Did it twice today pulling up at lights, its not the brakes.

You don't feel anything through the pedal, or feel anything coming through the steering, its audible only. Does it even under the lightest of braking and always just as the car is about to stop. its very quiet and would have easily been drowned out by the exhaust being holed. Both events today were in a straight line.

I am beginning to think something that's not nice is going on with the drivetrain.

[mannyo]

More diagnosis, this is quiet worrying and not sure what to make of it. I'm picking up the buyer of my D2 from Salisbury on Sunday, so another pair of ears will be able to witness the fault.

The judder/shudder or whatever you want to call it happens as I say when stopping, but it does it in both 'D' and also when coasting to a stop in 'N'. You do not have to be on the brakes either, it will sometimes do it just coasting to a stop in 'N' with no feet on any pedals. The speed concerned is less than 1mph, you could walk faster than the speed where the sound occurs. If I brake hard to a stop, nothing the car pulls up fine everytime.

Thought maybe its a dodgy engine mount, so this evening I opened the bonnet put the car in D and foot on the brake, then pressed the accelerator, the engine hardly moves. Tried reverse with foot brake, same result so its not the mounts.

Then there is the quiet whine when at speed, no sound at all in town.

Scanned the car for fault codes as well, Engine - nothing, Auto Trans - nothing.

Weird, very weird.

[PsYcHe]

If it does it in N then unlikely to be the box... maybe a gearbox mount or suspension bushes.

the bmw and jag versions of the box are known for thumping into 1st when stopping (the wifes x5 does it).

[sarg]

Sounds like suspension bushes to me, somewhere on front arms

[mannyo]

The tyres are being replaced on Monday, all four.

I cleaned the car today, found the nearside rear tyre almost bald in the centre of the tread so obviously been overinflated at some point. Confirmed by the local tyre place, who did not have any tyres in 255/40x19 (sleepy Dorset for you).

I popped to the local garage to check the pressures, FR - 35PSI, FL - 35PSI, RR - 35PSI, and I was expecting a high reading on the otherside, but no RL was running at 20PSI so it was 15PSI down.

Tyres are all now 35PSI, the judder/shudder is still there, I'll report again once the new tyres are on.

[sarg]

I cannot imagine why new tyres would fix the shuddering

[mannyo]

Originally Posted by sarg

I cannot imagine why new tyres would fix the shuddering

Confirmed, it hasn't.

Four new tyres now fitted, and the best of the old ones transferred to the spare as it was an odd size. Will report if the whine is any different when I get to drive at 70mph again, not very often in Dorset as hardly any dual carriageways.