Wierd noise vibrations

[Ska]

OK somit has happened to my car;

Syptoms are as you start to accelerate at a good pace; not exactly gunning for it, I get this dull thud noise reatedly which increases in rate with acceleration. It seems less obvious with normal criuse. Also when I press the throttle slightly the gearbox is reluctant to change down and this vibration becomes more violent making the car feels like a bull ride ; almost feels like a throttle issue or misfiring under load The noise/vibrations seem to eminate from the drivers side front wheel assembly. Its worth noting that I have been away from my car for a couple of weeks and a friend has borrowed it; in this time it looks as if the CV grease has oozed out of the rubber gaiter even though ther is no sign of a tear anywhere but there is defo loads of CV grease riding my alloy wheel and wheel arch. May I have your learned opinions dear Sirs as I thought that if a CV joint went dry it would make a loud clicking noise

PS yes I will never let this FRIEND borrow my car again and there were no failt codes.

Your help as ever is much appreciated

[Duffy3074]

If there's CV grease everywhere then the joints gone, the click when lightly worn but can clonk/lock up when completely goosed.

Pop the driveshaft off and have a look.

[grdunn123]

I wouldn't drive it at all until you've had it diagnosed properly although it does appear to be a cv joint...you'll do loads more damage potentially if you're not careful

[LostKiwi]

Jack up the offending wheel and check for rotational play. Chances are the CV's gone and it will either turn fairly freely or clunk as you rotate it back and forth...

[SINGH]

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Jack up the offending wheel and check for rotational play. Chances are the CV's gone and it will either turn fairly freely or clunk as you rotate it back and forth...

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This has also just happened on a friends A6 theres also alot of grease around the area, how much would this usually cost to put right?

Thanks

[Ska]

The drive shaft has to come off and my mechanic friend is charging an hours labour around £45 plus the parts. What gets to me is the type of noise and the fact that it happens in a straight line and not necessarily on turns; the noise is more like a pillow being punched repeatedly and the car vibrates like the engine is missing big time.

I suppose the question is do I replace the whole drive shaft or just the CV joints because it looks like all 120g of the stuff is living on the inside of the wheel and wheel arch

[LostKiwi]

Chances are the inner CV is ok as it doesn't get the same stresses as the outer one (which has to transmit drive through much sharper angles). To a certain extent it will depend on what you find when it comes apart...

[Ska]

OK its not the outer CV joint just had it replaced and the contents of my wallet to the tune of £110

Mechanic reckons it might be the drive shaft/s after another test drive. What’s interesting is that there is a dull noise (increases with acceleration) along with ever increasing vibrations; the intensity of which is different for different scenarios:

Below 25mph hardly noticeable

25-45ish with light accelerator pedal low frequency but high intensity vibrations(car feels like its missing (holding back))

Above 45ish frequency increases more than intensity.

One things for sure at certain speeds I'm sure the car is visibly shaking to on lookers

After my mechanic changed the outer CV joint we had a look at the drive shafts for ecentricty or deformation by sticking it on the ramp with the engine running which allows the front drive wheels to spin. There didn't seem to be much "wobble" in these though the O/S did exhibit more movement than the N/S and the O/S one had a lot of thick paint bubbling off at what looks to be either a joint mid way or a balancing wieght (what does one look like on these?).

Frustrated at not being able to diagnose this I went straight to the Stealers (Fat load of good) the bloke came out sat in the car and said it was miss firing as he felt the car was holding back. So I came home had a look round on the tinternet to see if there were any similar things. I found something on the vortex forum the guys explains the symptoms almost identical to mine and he too went down the drive shaft route until the stealers eventually found that the fuel pumps (engine mounted one for each bank) were pretty much knackered so they were replaced and he was fine. Which bring me on to the next question; Does my ACK 2.8 30v have an engine mounted fuel pump? Secondly I know from experience that If there are spark issues your misfiring is intermittent is a miss fire due to fuelling probs more consistent through the rev range? Could the fuel filter be responsible?

Yours desperately Ska

[LostKiwi]

If its fuelpumps you should get a low fuel pressure error on VagCom - have you tried it on VagCom yet?

You could also try changing the fuel filter - if its clogged it may cause the same symptom. Failing that get yourself a coilpack, change one at a time and see if it goes away. If it is a coilpack (and they do fail with weird misfires - my Volvo seemed to idle fine but would miss under load sometimes when one of the 4 I had to replace failed). Chances are a coilpack won't post any errors on VagCom either.

[Ska]

Tried the coil pack change and spark plugs and changed the fuel filter; no change. But car feels more lively!

Also vagcomed it again and still no Codes, however, the vibrations are a bit worse and occumpanied by a repeated dull "whoom" (yes I know it the technical term ) on acceleration from the front right, which is saying to me drive shaft, so thats what I'm gonna change next unless someone has reasons as to something else like say bearings; but I always thought that was more of a continuous groan

[IT_S8]

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Tried the coil pack change and spark plugs and changed the fuel filter; no change. But car feels more lively!

Also vagcomed it again and still no Codes, however, the vibrations are a bit worse and occumpanied by a repeated dull "whoom" (yes I know it the technical term ) on acceleration from the front right, which is saying to me drive shaft, so thats what I'm gonna change next unless someone has reasons as to something else like say bearings; but I always thought that was more of a continuous groan

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This is interesting stuff, My A8 that I bought and used for about 10 miles before buying the S8 has a similar sounding problem, which started as a vibration and worsened to the point I cant drive it now. Its sat in our workshop waiting to try out donor parts (like I'll ever have time for that!). I came up with the following conclusion during my road testings if it helps:

1) noise/vibration was consistent with speed, not revs so not engine. Got it up to 40 and shifted using tiptronic to vary revs, but not speed and no change in problem

2) Got it in a car park with one person listening to wheel and drove very very slowly. Eventually picked up on a faint squeaking every revolution by the passenger wheel.

3) Turning the steering wheel (or not) made no difference whatsoever...

4) It got worst the more I drove it.

I concluded the N/S bearings are probably shot. If it were the CV joint, I'd expect turning to make a difference. Engine revs freely stood still and made no difference which gear I use at speed...

Dont know if that helps, but i'm very interested to see what you conclude. I'll let you know if I ever get chance to change my bearings over... I know we've got an action to check out some replacement shafts for you at the moment... I've been on hols, so Dave's on with it

[LostKiwi]

While you have it stripped down you may as well look at the wheel bearings too. Having read back through the thread the clue that the issue is near the wheel is that you said the wheel and inner arch liner was covered in grease. Got to come from somewhere... and if it isn't the CV the only other thing there is a wheelbearing.

Be real interesting to know what this is!!!

[Duffy3074]

Yep, this should be s simple one.

At least pull the pads out, turn the lot with the wheel in the air and feel for any play/roughness.

The clue is in the grease, it's come out of somewhere that needs it, so it's either a joint on the driveshaft (A common fault on any car, especially FWD)or the wheel bearing.

[Ska]

@ Ian thanks for that but there is one fundamental difference in that the vibrations; on my car they increase with speed and the noise is not a squeak and the vibrations are almost non existent below 30mph; I've read round on the internet that a squeak is normally associated with the inner joint.

What lost kiwi says about the bearing+ grease may hold the key; when we done the cv joint I had a quick glance from the inside at what looked like the bearing which was cover in grease but I couldn't gauge if it was damaged. The question is can a failing bearing cause so much vibration on its own or has this damaged the shaft as well? No damage to the spline but was insure about the trueness of rotation when we had a look whilst doing the outer cv joint.

As for free play; checks they were done but on a compleicated suspension set up as on this car there was not detected.

I think I might have to change the bearing first (least expensive first) though once you have the that undone its easy to put the replacement shaft in at the same time

[LostKiwi]

If the cage that surrounds the individual bearings has collapsed and started break up then it possible some vibration could be caused. Similarly if a bearing has fractured or got a flat spot, or if the inner or outer race has worn through the hardened coating it will cause noise, although in that case I'd be surprised if it gave no warning at all (usually this is the classic rumbing wheelbearing symptom).

Best pull it apart and take a look - not too much of a job and whilst its apart you may as well change it - not expensive at all!

[Ska]

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If the cage that surrounds the individual bearings has collapsed and started break up then it possible some vibration could be caused. Similarly if a bearing has fractured or got a flat spot, or if the inner or outer race has worn through the hardened coating it will cause noise, although in that case I'd be surprised if it gave no warning at all (usually this is the classic rumbing wheelbearing symptom).

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Thats just whats throwing me nothing in this A8 sounds like what it would in any of the other cars I have ever owned. I would expect a defective bearing to "groan" constantly but this is more like once every revolution of the wheel/shaft with the vibration ocumpanied at the same rate? turning the wheel can make it wortse for a bit which would then piont to the drive shaft also its less evident when you take your foot of the throttle which again says to me drive shaft as it happens a lot more when its being torqued up so to speak.

[IT_S8]

[ QUOTE ]

@ Ian thanks for that but there is one fundamental difference in that the vibrations; on my car they increase with speed and the noise is not a squeak and the vibrations are almost non existent below 30mph; I've read round on the internet that a squeak is normally associated with the inner joint.

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My vibrations do increase with speed, just during actual acceleration they ease of slightly. Maybe the front of the car lifts slightly, taking weight of the bearings, who knows...

Squeak is a bad term, its more of a rubbing noise, exactly one revolution, barely audiable at low speed. I have no noticable vibrations until about 40mph +

Sounds very similar still.... Im hoping I might have chance on Friday to jack it up and give it some attention.

I'll probably change both the shaft and bearings though while im in there, unless it becomes blatently obvious that only one is at fault....

I'll let you know what I find if you dont fix yours first

[Duffy3074]

A strip down is the best way to have a look, chances are it's something simple. A bearing, a bent/worn shaft or even a clapped disc or even a brake pad with a stone/other misc bit of poo stuck in it.

You'll sort it.

Worst case scenario is the bearing on the output from the diff but that wouldn't leak grease (It runs in oil)

[Ska]

I doubt it anything to do with the brakes, in fact last night i took the car for a quick spin and tried to induce the vibrations again but htis time as the vibrations became most tense I slipped the Gbox into Neutral which immeadiately stopped the vibration by 90%. This says to me that the shaft is out of balance slightly and that it only really vibrates intensly when loaded by the engine which points more to torsional forces acting on it due to bad inner U joint, heres hoping...

[Duffy3074]

It was justa suggestion rather than a definitive answer.

Strip it down and I'm sure all will be revealed.

[LostKiwi]

Still doesn't explain the grease though......?

[Duffy3074]

This true.

The grease is definitely a clue!

[bargepole99]

I've only just seen this thread, but here goes. After my recent 60,000 mile service by a non-audi tech, I took my A8 to Poole Audi for them to give it a 'once over' as there was a very slight vibration when braking, and I had just had new new discs and pads fitted all round. I went out with the 'official' for a test drive and he thought the car was ok but recommended it be hoisted up and checked out underneath. They found a gaitor leaking so I ordered the part and a new CV joint. They also noticed a nail in the NSR tyre. On my way home I stopped at a tyre specialist to get the tyre fixed and mentioned about the leaking gaitor and how much it would cost to get the tracking done with their fancy laser kit after the new CV joint had been fitted. The reply I got was that the work should be entrusted to an official Audi dealer because the last time they had an A8 Quattro brought in for tracking it took them ages to 'try' and get everything correct. I took this advice and ended up going back to Poole Audi who did the job, found out that an additional component required replacement, and aplologised that the total cost, including tracking, had gone up from £96 to £116. All this work was done while I waited and I could see the car being worked on from the 'visitors' centre' for almost 2 hours. The result... After driving no more than a couple of hundred yards the car was clearly unlike it had ever been before - it was driving like a new car - and still does. My conclusion is that, perhaps, some jobs are best tackled / most efficiently done by specialist Audi mechs - and I don't have any connection with Audi at Poole or anywhere else !

Anyway, good luck with getting your problem sorted. I do know how frustrating these things can be.

David

2000 A8 LWB

[Ska]

OK an update tried fitting a new shaft but it was too short so whilst I was at the garage I got the mechanic to do a quick test.

We removed the wheels and secured the brake discs, then raised the suspension to simulate normal ride hight. We then ran the engine up to about 1500rpm and looked for play in the drive shaft. Except we didn't find anything significant in the shafts. However, we did find this wierd oscillating play in the flange shaft/u-joint end. the fisrt video is when the engine was run upto 1000rpm (15-20mph) and found that it kept sticking and each time it stopped the flange assembly moved slightly eccentricaly. On the second check we held the disc to stop it rotating whilst the gearbox was in "N" you can see a little clearer this motion. My thoughts are that the flange shaft is knackered but from what I can see it bolts straight on to the diff. with a single alan bolt are their any bearings for it that could go bad? or is my diff. shot.

PS the passenger drive shaft behaved much better.

A penny for your thoughts

top is my drive shaft:

[LostKiwi]

Hmmm... looks a bit odd. There is a bearing on the outer end of the shaft just behind the cover bolted to the gearbox casing. If you do go in there you may as well replace the gearbox seal at the same time.

To see what it looks like log on to www.vagcat.com and look at the detailed parts diagrams.