Vibration under acceleration = unwanted butt massage

[JulesB]

I've developed some severe vibration (full seat-of-the-pants massage chair style) during acceleration and I'd appreciate any expertise anyone can offer. I realize this subject is well-traveled territory, but I figured I'd submit my particular case.

2001 6MT allroad, 173,000 miles, stage 1 chip.

Pertinent service history: both front CV axles replaced within the last 25,000 miles, new ignition coils and plugs in the last 15,000miles, both ICUs replaced 2000miles ago, driver's side outer tie rod end 4000miles ago.

I'm not experiencing engine misfiring issues, and I sincerely believe this is a drivetrain issue. No MIL, no other lights, no significant vibration with clutch disengaged (although I have not yet had a helper rev while looking at the engine to diagnose engine mount issues, which I am sure could use replacing), still shifts through all gears pretty smoothly. The vibration does not really start bucking while the car is cold, but after about 10-15 miles it starts kicking in. It's most severe under acceleration but will also vibrate while coasting downhill in gear. On flat road with minimal gas needed to maintain speed, the vibration is more subdued, but still present. Smooth sailing while coasting in neutral.

I tested acceleration with traction control on and off: no difference. Changing ride height didn't really seem to effect the severity either.
1st gear acceleration doesn't seem to shudder as badly, but anything from 2nd on up vibrates under acceleration.

I've pulled n' prodded on all control arm components n' such and I'm not feeling excessive play anywhere. I tried my best to get a look at the driveshaft hanger bushing with the exhaust on, and it still looks to be intact, but I can't really tell.

I've read a lot of posts blaming the front cv axles for this vibration, but I do not believe that to be the case here. I've also heard tales of unbalanced tires, but I don't believe that's the case here either (the cold vs hot phenomenon).

Last bit of pertinent info: I believe the clutch is original, which seems like a helluva long run; it would stand to reason that she's done for. I also have not seen any records of any transmission service ever completed.

My main questions: Could a failing clutch cause this type of vibration under load? (I've never experienced any jumps in RPM from clutch slippage). Just yesterday I changed the rear diff fluid just for the hell of it: no change in vibration. Is changing the front tranny fluid a good idea in the diagnosis process? Is there any chance wheel hubs/bearings could manifest vibration in this way? I am planning on doing motor mounts and transmission mounts as soon as possible for sure. I just don't understand why the vibration wouldn't pop up regardless of cold or hot if mounts were the issue.

Thanks a lot for any insight folks!

[rollerton]

Leavenworth? No ways!
For this problem you sort of have to narrow troubleshooting down to parts that rotate and what the nature of the rotation is relative to what you feel and how the car is moving.
I'm always prone to blame the driveshaft for issues like this (because I had a BAD one that did something like this). But it's a very difficult thing to diagnose actually. My reasoning is that the main rotating assembly that undergoes stress under acceleration is the axles and driveshaft.
The driveshaft aspect/angle changes the 'most' when you accelerate and decelerate, and mainly at the ends. I also like to blame the drievshaft ends because they're very easy to swap out to see if it helps. The center support is not as easy. But if you can get under the car to inspect the center support of the driveshaft you may find something also, but I've been told the center bearing can be really quite loose and not be the cause of vibrations- you have to remove the exhaust shield to see it. Keep in mind that the Allroad driveshaft is specific to it, especially the manual, can't just grab an A6 part- though it would probably fit it wouldn't be correct.

Other considerations, like the clutch..yeah, could also be part of it considering you feel no problem when in neutral. Unfortunately this ends up being another part-time job swapping out parts until one day you get lucky.

[02 A6 2.7T]

Leavenworth? No ways!
The center support is not as easy. But if you can get under the car to inspect the center support of the driveshaft you may find something also, but I've been told the center bearing can be really quite loose and not be the cause of vibrations- you have to remove the exhaust shield to see it. Keep in mind that the Allroad driveshaft is specific to it, especially the manual, can't just grab an A6 part- though it would probably fit it wouldn't be correct.

Someone local with lots of previous vibration issues could probably test drive it and offer some wisdom ...
Usually if the vibration is most noticeable in the seat it's probably a gearbox or center driveshaft related issue. If it was control arms or front CV axles you would feel it in the steering wheel.
If it turns out to be the driveshaft center bearing, there's a replacement specifically for the allroad from 034 ... https://store.034motorsport.com/driv...bs_description

[JulesB]

Leavenworth? No ways!
For this problem you sort of have to narrow troubleshooting down to parts that rotate and what the nature of the rotation is relative to what you feel and how the car is moving.
I'm always prone to blame the driveshaft for issues like this (because I had a BAD one that did something like this). But it's a very difficult thing to diagnose actually. My reasoning is that the main rotating assembly that undergoes stress under acceleration is the axles and driveshaft.
The driveshaft aspect/angle changes the 'most' when you accelerate and decelerate, and mainly at the ends. I also like to blame the drievshaft ends because they're very easy to swap out to see if it helps. The center support is not as easy. But if you can get under the car to inspect the center support of the driveshaft you may find something also, but I've been told the center bearing can be really quite loose and not be the cause of vibrations- you have to remove the exhaust shield to see it. Keep in mind that the Allroad driveshaft is specific to it, especially the manual, can't just grab an A6 part- though it would probably fit it wouldn't be correct.

Other considerations, like the clutch..yeah, could also be part of it considering you feel no problem when in neutral. Unfortunately this ends up being another part-time job swapping out parts until one day you get lucky.

Ah! A fellow central Washingtonian: Cheers good sir! Are driveshaft ends easy to source? And when you say "easy to swap," how easy compared to all the hard-as-hell things that these beasts have to offer!? Also, is changing out the trans fluid at 173K likely a good call?

[JulesB]

Someone local with lots of previous vibration issues could probably test drive it and offer some wisdom ...
Usually if the vibration is most noticeable in the seat it's probably a gearbox or center driveshaft related issue. If it was control arms or front CV axles you would feel it in the steering wheel.
If it turns out to be the driveshaft center bearing, there's a replacement specifically for the allroad from 034 ... https://store.034motorsport.com/driv...bs_description

Ha! I'd gladly let anyone get a free butt massage from this thing if it might help diagnose the gremlins!

[rollerton]

Ah! A fellow central Washingtonian: Cheers good sir! Are driveshaft ends easy to source? And when you say "easy to swap," how easy compared to all the hard-as-hell things that these beasts have to offer!? Also, is changing out the trans fluid at 173K likely a good call?

I'm actually just down the street in Wenatchee! And I have a pile of parts of junk and stuff if you ever need anything random. Like driveshaft CV joints. How 'bout some wheels? Need to get rid of some
@ 170k miles...you might want to change the fluid and filter. I wouldn't go any further though. If it's driving okay now clean fluid will help, but flushes and trans additives will probably not be a good idea.
Ever need any help with anything hit me up, ..have VagCom and some crappy tools.

[bpark1210]

I'm actually just down the street in Wenatchee! .

My vote goes for drive shaft . . . either the CV joints or center bushing. I'm experiencing the same at the moment. I noticed a little bit of a soft whine that sounds rotational at idle. When I accelerate hard there seems to be vibration at higher rpm loands. Conundrum for me is to replace the drive shaft CV joint which requires a pull of the entire assembly or just cough up for a 01E swap since it's a quarter of the work.

Rollerton, you're in Wenatche? I'm heading there April 9-11th to visit a good buddy to help w/ his new home and truck maintenance. I'll be taking the S6 out there since my Passat refuses to start up, you interested in meeting up and showing me your 6mt swapped S6?

[rollerton]

Passat refuses to start up, you interested in meeting up and showing me your 6mt swapped S6?

Hey!
Yes! Absolutely..hit me up whenever you'll be close. I'd love to show you the ...manual S6, but...it went to a new home a couple months back. It was a dumb thing in retrospect, I do not feel like I came out ahead, but I still have two other S6's plaguing me. As of now they're both auto's.
My wife still drives a silver one like yours; except hers looks like one of those off road buses they haul chickens in down in Brazil. It's fucked up, she beats the fuck out of it and the chain tensioners are just rattling away like a machine gun. Yeah. I have TWO 4.2 chain tensioner jobs sitting in front of me.
And ...it'll sound strange, but my girlfriend is driving the high miles Polar White S6 that came from Thaddeus in Wisc. I'm rolling a mint condition white B6 USP Avant as of now and will eventually take hold of the white S6.
Anyway, yeah, I'm always around..love to see that beast you resurrected. We Need a group buy 01E swap deal from somewhere!

[alfissimo]

Driveshaft support. Get some 3m windshield glue and fill the support with it, let it sit for a night or so then it should be good to.

[02 A6 2.7T]

Passat refuses to start up, you interested in meeting up and showing me your 6mt swapped S6?

I recently completed the TDI 01E swap on my S6, and I believe I'm in your vacinity ...

[bpark1210]

I recently completed the TDI 01E swap on my S6, and I believe I'm in your vacinity ...

You must be the one Dre was helping. I'd love to meet up sometime and check it out. I'd want to pull the engine like you did to address a couple small coolant leaks. I'll pm you sometime to meet.

Sent from my Nexus 5X using Tapatalk

[02 A6 2.7T]

You must be the one Dre was helping. I'd love to meet up sometime and check it out. I'd want to pull the engine like you did to address a couple small coolant leaks. I'll pm you sometime to meet.

Sent from my Nexus 5X using Tapatalk

I am the one ... Dre and I have been doing stupid crap on our Audis for a few years ... lol

Sold him the Atlas allroad he had before the S6 ... I did a custom alcantara sport interior in it before I bought the S6 and decided to sell the ar ...

I've been following your thorough build thread and would love to check out your S6.

I bought the aluminum oil cooler coolant pipe and installed it with the engine out (one of the reasons I went the full engine-out route).

Glad I did, as it was an absolue bitch to get the oil cooler off without stripping the notorious top-center allen bolt ...

Picture of the allroad interior ... build thread here

[bpark1210]

Hey!
Yes! Absolutely..hit me up whenever you'll be close. I'd love to show you the ...manual S6, but...it went to a new home a couple months back. It was a dumb thing in retrospect, I do not feel like I came out ahead, but I still have two other S6's plaguing me. As of now they're both auto's.
My wife still drives a silver one like yours; except hers looks like one of those off road buses they haul chickens in down in Brazil. It's fucked up, she beats the fuck out of it and the chain tensioners are just rattling away like a machine gun. Yeah. I have TWO 4.2 chain tensioner jobs sitting in front of me.
And ...it'll sound strange, but my girlfriend is driving the high miles Polar White S6 that came from Thaddeus in Wisc. I'm rolling a mint condition white B6 USP Avant as of now and will eventually take hold of the white S6.
Anyway, yeah, I'm always around..love to see that beast you resurrected. We Need a group buy 01E swap deal from somewhere!

That's a lot of avants in the family. I'll hit you up over that weekend. I might be free on that Sun or Mon before I leave back to Seattle. Group buy would be great if Scotty would offer it.

[bpark1210]

I am the one ... Dre and I have been doing stupid crap on our Audis for a few years ... lol

Sold him the Atlas allroad he had before the S6 ... I did a custom alcantara sport interior in it before I bought the S6 and decided to sell the ar ...

I've been following your thorough build thread and would love to check out your S6.

I bought the aluminum oil cooler coolant pipe and installed it with the engine out (one of the reasons I went the full engine-out route).

Glad I did, as it was an absolue bitch to get the oil cooler off without stripping the notorious top-center allen bolt ...

Picture of the allroad interior ... build thread here

That's the exact reason I would want to pull the engine too. I've got a bufkin pipe sitting collecting dust as well as 2 o-rings for the rear coolant pipe that drips onto my cat, sounds like I'm grilling some juicy hamburgers under the hood as it drips haha.

Is that an alcantara dash on the ar?

[mbandit]

My similar vibration was not driveshaft ends or center bearing....it was the center u joint. Pulled the driveshaft out and rotated past what's was normal driving angle and it bound up so much that it was stuck at a 45 degree angle.

[SteelyS6]

Hey!
Yes! Absolutely..hit me up whenever you'll be close. I'd love to show you the ...manual S6, but...it went to a new home a couple months back. It was a dumb thing in retrospect, I do not feel like I came out ahead, but I still have two other S6's plaguing me. As of now they're both auto's.
My wife still drives a silver one like yours; except hers looks like one of those off road buses they haul chickens in down in Brazil. It's fucked up, she beats the fuck out of it and the chain tensioners are just rattling away like a machine gun. Yeah. I have TWO 4.2 chain tensioner jobs sitting in front of me.
And ...it'll sound strange, but my girlfriend is driving the high miles Polar White S6 that came from Thaddeus in Wisc. I'm rolling a mint condition white B6 USP Avant as of now and will eventually take hold of the white S6.
Anyway, yeah, I'm always around..love to see that beast you resurrected. We Need a group buy 01E swap deal from somewhere!

Group buy on TDI 01E's, best thing I've heard i awhile, count me in! I really think 6spd swapping my S6 would rekindle the love affair, everyone keeps saying how awesome it is!