Help me determine this VIBRATION.

[europaisch]

I have a vibration that I cannot determine. I need help and ideas. Here's where I am.

Car: 2008 Audi A4 Avant Quattro. (Coilovers, 19s, BBK)

Vibration:

- Starts at about 55mph and is present up through 80mph.
- Vibration is felt in the seats, floor and the gas pedal. (cups and water bottles rattle)
- All four control arms, corners of the car show vibration when ran on the rack. (Update 11/3/14)
- Not in the steering wheel.
- Not present during braking.
- The vibration has a pulsating rhythm. It oscillates from light to strong on a very specific almost heartbeat rhythm. The driveshaft is the easiest place to 'see' the rhythm of the vibrating. (Updated 11/3/14)

Failed Solutions:

- Tires. Originally thought it was a imbalanced tire. Took tires to three different tire shops including one with a road force balancer. All three confirmed a tire that wouldn't balance. Bought an entire set of new tires. Still had the vibration.
- Wheels. My next thought was that I had a bum wheel. Bought a brand new set of wheels. Still have the vibration.
- Suspension. For good measure I replaced my Eibach/SLine/S4 perch with Stasis Streetsport COs. Still have the vibration.
- Axles. I had both front axels replaced. Still have the vibration.
- Rear Differential. Replaced the rear diff. Still have the vibration through the entire car. (Updated 11/3/14)

Please help me shed some light on what could be causing this annoying vibration.

Dirty pic for clicks after an 17+ hours on the highway.

[ChipsöfSix]

Thinks I would check are
Control Arms ( bushings could be beat ) and when was the last time you got an alignment ? Does the car dart when your driving ?

[aluthman]

Is it a high frequency vibration or a low frequency one? I had a low frequency vibration that turned out to be a loose motor mount.

[Maiky]

cv joint cause vibrations at acceleration

[kegobeer]

cv joint cause vibrations at acceleration

He replaced both axles - which includes the CV joints.

[europaisch]

- It's not alignments. I've had many over the life of the vibration. Including one a month ago.
- No vibration at acceleration.
- Can't speak to the motor mount solution as the vibrations seems to onset at speed. (Lord knows they could be replaced, the 2.0T motor feels like a diesel.)

[kegobeer]

You've replaced most of the things that would cause vibration between certain speeds. Might as well replace the tie rods (complete, not just the outer). If they are worn you could get some shimmy at high speeds.

[dalmation53]

You've replaced most of the things that would cause vibration between certain speeds. Might as well replace the tie rods (complete, not just the outer). If they are worn you could get some shimmy at high speeds.

check upper control arms,tie rod ends inner and outter. check strut mounts too those ******s go back sometimes..

[europaisch]

Thanks for all of the great suggestions. I'll check out the UCA, tie rod ends and strut mounts while I'm at it.

[Sanjman]

just more ideas... motor mounts, snub mounts, go to a tire shop and make sure each wheel/tire combo is balanced properly. Maybe the weights came off of them. I remember having ice stuck on the wheels and had the same issue. I left the car in a heated garage and knocked all the ice off each wheel it the vibration went away. Of course you're in the bay... where there's snow and desert haha. who knows anything goes.

[midnight407]

silly question but...I would assume you have hubcentric rings in there, right?

[europaisch]

Thanks Sanjman. I'll check out the mounts. As for the imbalance, the vibration is consistent across multiple sets of wheels and tires. It's not a wheel/tire issue.

Yes Midnight hub centric rings are there.

[drumnjuny]

i've been chasing a similar rattle forever. good luck! i'm going to do control arms (supposed to show up this week) and see if that fixed it.

[Acme]

You say it doesn't vibrate under acceleration, does it actually stops while you accelerate, or you say that because it does vibrate but it's not worse when you accelerate? I'm asking because I have a very similar issue, but in my case it does vibrate under acceleration but it's not related (i.e. the vibration is still there when I cruise, even when in neutral).

[kr3w45]

Does the vehicle shake when brakes are lightly applied?

The first thing I would check if you have already checked wheels/tires/suspension/driveline would be the brakes. There is a chance one of the calipers is hanging up or sticking and warped the rotor causing a vibration when the brakes get hot. Check the front and rear, look for discoloration in the rotors.

[Jake@JHM]

Have you looked into your drive shaft support? These are known to have a vibration felt on the highway when they have gone bad.

http://jhmotorsports.com/shop/catalo...-a6-p-792.html

These bearings fail and can cause different levels of vibration depending on how bad it has failed.


In addition to warped rotors, pad deposits are usually the cause of vibrations from brake components which would feel the way you would imagine a warped rotor to feel like. Check if you have any black spots on the rotor little or big.

[drumnjuny]

Have you looked into your drive shaft support? These are known to have a vibration felt on the highway when they have gone bad.

http://jhmotorsports.com/shop/catalo...-a6-p-792.html

These bearings fail and can cause different levels of vibration depending on how bad it has failed.

what are the symptoms for this besides the vibration? how can you tell if its gone bad? i'm not even at 100k yet but i do drive the car pretty hard and owned it for the last 40k so i'm curious if this could be it.

i'll be sure to report back as to whether the control arms fixed the issue

[Jake@JHM]

The only real symptom is vibration because it is a bearing with a spinning shaft going through it.

[drumnjuny]

is there a visual inspection that would prove its faulty? install looks like a bitch so i'm gonna need to be 100% sure i need it before swapping it out haha

[europaisch]

Thanks for the great insight and replies. It's not brake related, no vibrations in brakes or while depressing the brake pedal. I had the vibration before, during, and since then, I've upgraded to a BBK kit. Plus, I recently had the calipers rebuilt. Rotors are mirrored, spot free.

Jake makes an interesting point. It's a rotational vibration, shows up at speed.

[Mister W]

vibrate but not in the steering, i'll say look at the back, tire got worned oddly, bearing, lug bolts not tight evenly, damaged wheel, unbalance disc.
Try braking with the e-brake to see if it change something.

[europaisch]

Mister W - Wheels Tires are new and properly balanced. Vibration has been there through 3 different sets of wheels and tires. Braking doesn't change anything.

[kegobeer]

I've seen the wrong hub centric rings cause this kind of vibration.

Have you replaced tie rods yet, or checked the steering rack?

[europaisch]

Haven't replaced tie rods or checked the steering rack. Wouldn't a faulty steering rack cause a wobble in the steering wheel? I have no wobble in the wheel.

[Jake@JHM]

DSS?

If you get tired of chasing it, bring it by. We will diagnose it for an hour of labor.

[kegobeer]

Haven't replaced tie rods or checked the steering rack.

DSS?

If you get tired of chasing it, bring it by. We will diagnose it for an hour of labor.

That's what I would do.

[drumnjuny]

DSS?

If you get tired of chasing it, bring it by. We will diagnose it for an hour of labor.

god damnit. i paid an hour and a half at 3z3 and they just used dial calipers to tell me that the hubs were warped didn't even look at the control arms or steering knuckle or anything else i asked about / said i suspected...

Jake fly out here and help me diagnose this shit lol

[pauldupuis]

check you wheel bearings. if there is a humming noise associated with you vibrations i would put money on it. if its felt in the pedals and the seat usually that means its the rear wheel bearing. if the vibration is in the steering wheel which i know you said its not it would be front wheel bearings. i see these all the time on all different makes. pot holes help in making them worse.

[europaisch]

Keeping everyone updated for prosperity.

Ran the car on a rack today with no wheels and tires. Still has a vibration. Tracked it down to the rear diff. As the car approaches 5th-6th gear the vibration starts occurring in the rear. The rear diff. starts making a rattle/grind type sound. As soon as you left off the gas the vibration goes away. It sends the vibration up front too.

Outlook not good as I may be having to replace a rear diff. Gulp!

Anyone have any insight into if B7s are prone to having the rear go out?

[Jake@JHM]

That isn't common, but we do have something for you! http://jhmotorsports.com/shop/catalo...on-p-1888.html

[vtwinjunkie]

Just curious. Have you ever had the rear diff serviced on it before?

Keeping everyone updated for prosperity.

Ran the car on a rack today with no wheels and tires. Still has a vibration. Tracked it down to the rear diff. As the car approaches 5th-6th gear the vibration starts occurring in the rear. The rear diff. starts making a rattle/grind type sound. As soon as you left off the gas the vibration goes away. It sends the vibration up front too.

Outlook not good as I may be having to replace a rear diff. Gulp!

Anyone have any insight into if B7s are prone to having the rear go out?

[europaisch]

Not to my knowledge. And I'm the only owner.

Some more insight, got in touch with Audi of America. The rear diff. for this car is currently on backorder from Germany. There are no B7 Avant quattro rear diffs in all of North America. Suspicious, like maybe that's a part prone to premature wear.

[Jake@JHM]

Not to my knowledge. And I'm the only owner.

Some more insight, got in touch with Audi of America. The rear diff. for this car is currently on backorder from Germany. There are no B7 Avant quattro rear diffs in all of North America. Suspicious, like maybe that's a part prone to premature wear.

Likely because its a large part that doesn't sell often, so AOA won't waste time stocking it.

[geebus]

[JayDog747]

How many miles do you have on the car?

[europaisch]

140k

[JayDog747]

140k and you never changed the rear diff fluid?? You may want to take care of that right away.

[europaisch]

Car has been properly maintenanced at all the proper intervals. Checked the rear fluid levels again today, nothing to cause alarm.

[konarider94]

I had an issue that sounds just like yours and it turned out to be the bearing on center torsen differential. Couldn't tell on the hoist if the source up front or out back because the center diff was putting vibration into the whole drivetrain. The bearing is toast on this, I replaced the whole trans because at the time I didnt know the issue and couldnt have the downtime. Looking at the picture you can see the worm gears has some sort of galling/pitting occuring on the wear faces anyway. At first the bearing feels okay but at some spots you can feel flat spots on the balls and only sometimes it will rattle pretty good just spinning it by hand. Its fairly easy to pull out and check. Picture of mine to help verify the story.

It may be your rear end like you speculate, but Im sharing this as another possibility. I really noticed it in the speed range you said. Its a 6010 bearing. You can calculate failure frequencies of that if you have a way to measure the vibration. I tried using a fft program on my phone but the mic wasnt sensitive enough to pick it up from all the extra noise.

[chris@fifteen52]

I would try some Motul 300 in the rear different and see if that helps.