Mystery Vibration

suspension
audi
a6

#1

I?m having a vibration problem with my 2001 A6 2.7t 6-spd. It is equipped with the sports suspension option and has 104k miles on it, 50k of which I?ve added since I purchased it four years ago.

It all began in May when a serious rhythmic, speed dependent noise started emanating from the car; front driver side. I took it to one of my two favorite independent shops and they diagnosed and replaced the front lower control arms and bushings. This eliminated that problem but a couple of days later, when I had occasion to be driving at highway speeds, I noticed a (admittedly slight) speed-dependent vibration that hadn?t been there before. I took it back to them but they claimed they couldn?t even detect it and so couldn?t begin to diagnose it. ?We don?t know the car as well as you do and can?t feel anything funny, at least not to us? said the shop manager.

So I then took it to a second independent shop who was able to confirm it present at highway speeds. He examined the control arm installation and found no fault with that as well as the balance of the suspension components and instead faulted the tires (two were worn down pretty good, two still had adequate tread). Four new tires later, and three separate attempts at balancing them (including ?road-force? balancing) the vibration was still there. He even returned two of the tires on the suspicion of a defect but to no avail. He also replaced the wheel centering adapter-rings suspecting as they were old and brittle and had become compromised. I will add here that with each successive effort at working the tire issue (be that re-balancing or replacing) the problem seemed to improve slightly, finally confining itself to between 62 and 79 mph. (And actually, I haven?t yet taken it beyond these speeds). Then again, it could also just be me, desperately wanting to believe it was improving??.

Failing with the tire remedy, this second guy thought it might then need a rebuilt driveshaft assembly since the vibration didn?t seem to be ?in the steering wheel? or isolated to any specific corner, but rather was that sort of ?whole-body? vibration that (in the old days when I actually wrenched on cars) used to signal u-joint problems. He added that he found the boot around the front joint had a small tear that might have allowed debris to enter and/or grease to escape, further corroborating the possibility that it could be the culprit. However he then also added that the tear was very small and the joint and driveshaft didn?t actually seem to have been compromised; i.e., it all seemed tight and in good working order.

Now then, the total cost to have him install a re-manufactured driveshaft assembly would set me back $900+, and with no guarantee of success. And, if it doesn?t solve the problem, the part would also not be returnable to the supplier (since it had been installed in a car). Having already replaced all four tires to no effect, and having little appetite to continue throwing good money at potentially unnecessary parts, I decided I ought to break down and take it to a full-fledged reputable Audi dealer where their ?experts?, intimate with the odd nuances that make Audis Audis, would quickly diagnose the problem, (the theory being that there could be no better authority than they, at $135/hr. of course).

The Audi dealer pronounced the car ?fit-as-a-fiddle?, nearly congratulating me on the solid condition of the entire drive train and suspension. ?Not even a motor or transmission mount? I challenged? Nope, said they; she?s as tight as they come; exemplary for its age and miles. I had counted on the normal tendency for most dealerships (and my prior experience with this one) to hunt relentlessly for any work they can charge you for, even work you didn?t know you needed. In the process of ?exposing? this inevitable litany of issues, one would be the actual problem causing the vibration. So I was surprised, if not somewhat confused, that they found nothing in the car?s own components to replace. It?s worth noting too here that they didn?t mention the small tear in the front joint boot (and I had deliberately not mentioned it to see if they would notice it) which makes me question how thoroughly they actually examined the car. And I will also add here that the independent mechanic who claims to have found it, while not an Audi expert per se (and so limited in his ability to find evasive ?brand-specific? problems like these), nevertheless has my complete trust and so I do not doubt that the tear is actually there.

Instead, the Audi dealership declared: ?It?s those aftermarket wheels you have on the car?. Well, in the 50k miles I?ve owned it, it has had the same set of Oettinger 17? rims it came with, and the car has never had this vibration problem before. That doesn?t mean the wheels can?t now have a problem, but they didn?t have any such problem two months ago. Now given that Pennsylvania competes gamely every year to win the honor of having the nation?s worst roads, and boasts one of the most efficient ?Departments of Pot-Hole Installation? anywhere, it?s possible that the car was so victimized and a barely perceptible bend in a rim is the result.

On this last possibility I?m thinking of taking it back to the Audi dealer and having them swap known good wheels/tires from another (pre-owned) Audi onto mine, to see if the problem goes away. (Frankly, I don?t know why they didn?t think of that given that they believe the wheels to be at fault.)



I?m not adverse to spending money as long as it actually solves the problem but I loathe the idea of swapping parts with no apparent reason, especially when I?ll be stuck with them. At present, the car is not a ?complete? Audi, lacking the requisite driving refinement at highway speeds. I used to brag that the car really began to ?settle down? at 85 mph and above, assuming a completely stress-free composure where one could ?drink tea with pinky properly extended?, characteristics for which Autobahn-engineered German cars are famous. Now I don?t want to drive it past 60! So I?d appreciate any other suggestions anyone might offer, especially since I?m betting against the wheels as the cause of this problem.



Thanks for your help,



Len Dube

Exton, PA


#2

Hmm-m-m…Obsession? Or undiluted Passion?I can relate.Word for word.Almost.I shall try to be brief.Le’ssay I were to change your Audi to a Volvo 265 with the PRV engine ,that wore her 343,000 miles with the power and grace of Nureyev;[unavoidable mixed meta.]I too have walked this costly road.As you are now,I once was.Nine months into this quest I was slotted into another recommended shop. Even the Pros’ who tended the F.H.P. steeds were stumped.You see after whittling down the list ‘of probables’ they were now as determined to find AND elimenate that Shim an’ shiver that showed itself only at 63 mph.aargh!My sweet spot.Many moons and mucho diniro have passed when,everybodies favourite uncle happened in that day as was his want.He listened quietly to the collective litany of fixes.As he repacked his pipe he said to no one in particular"Did anyone check to see if the driveshafts were out of round?"A split driveshaft meant another u-joint .That one is set in a rubber center carrier bearing,and both had been replaced with Volvo factory parts.Now,in all of central Fla. there was only shop with the equipt. to spin each shaft to speed…shoot it with a laser…mark it…A man in Ocala ,who’d add the weights accordingly .No MO Humm!Who Knew? If I learned one thing,it is this.It’s not what you hum but how you hum.


#3

Interesting…were I a betting man I’d say driveshaft as well, despite the Audi dealer saying otherwise. The $900 doesn’t bother me if it fixes it!
Thanks. I’ll post in later when I know more. I still want to eliminate the wheels/tires first though!