High Speed Vibration Troubleshooting Help Needed...

[SVOMikey]

Help! I’m at wit’s end. I have a high-speed (78-85mph) vibration in the front of my 2015 GTI/PP w/manual gearbox. It has been there since the day I got it off-lease from dealer w/ 25K miles. It is felt in the seat and a little in the steering wheel. Months later I jumped a curb and replaced all of the front right suspension, all wheels, tires and bearings. Vibration was still there. Threw the car on a lift and ran up to speed with LCAs & wheels dangling in the air. LCAs were flopping around quite a bit. I Jammed a crowbar in between the LCA and frame and it died down a bit. The LCA bushings were very sloppy.

I took it to a shop that said it was the right CV axle. They swapped with new OE axle and said it was happy. It is not. Still there.

I swallowed my pride and brought it to the dealer. Worst auto experience of my life. To escape any liability, they refused to listen to me when I said it did it from day 1 and blamed the tires/wheels I put on as well as the subframe which had slight damage from running up on the curb. Basically, all stuff changed months after the vibration was 1st noted.

Out of spite I have gone to the Audi aluminum subframe and a solid rubber LCA lower bushing and it hides the vibration quite a bit with the harsher ride but it’s still there. The car feels like it has a full set of coil-overs just from changing to the solid TT bushing!

So... The car has new aftermarket wheels/Michelin tires, all new OE suspension on the right front, new rotors, pads, wheel bearings (all 4), new OE Right CV axle. The car aligns perfectly. The tires have been road-force balanced a few times and it may help a little but does not eliminate the vibration. Again, the subframe and rear LCA bushings have been changed.

The car has the original left front suspension and CV axle. My local CV shop says they have no way to tell if the axle is bent. I thought they could spin it like a driveline shop does with a prop shaft but they claim no dice. The shaft is so far above the subframe I really doubt anything damaged it. So I really go to worst case scenario and think it’s the output shaft of the diff. Thoughts?

Today I stuck a run-out gauge on the ends of the CV axles but couldn’t get on the joints themselves. Both original and new shafts seem to have about 5 thousands of play on the painted surface at either end of the axle before it goes into the joint. It is likely not a valid test. I also stuck it on the vented edge of the brake rotor and saw about the same number. Again, both new and old look about the same.

So it turns out ATS makes a fantastic NVH test set for finding stuff like this but no one in CO or NM has one. )-:

Any suggestions on next steps? Any shop recommendations in Colorado that has enough of a clue to help? Thanks all. Sorry for the long post. Mikey in Denver.

 

[Superfreak]

Help! I’m at wit’s end. I have a high-speed (78-85mph) vibration in the front of my 2015 GTI/PP w/manual gearbox. It has been there since the day I got it off-lease from dealer w/ 25K miles. It is felt in the seat and a little in the steering wheel. Months later I jumped a curb and replaced all of the front right suspension, all wheels, tires and bearings. Vibration was still there. Threw the car on a lift and ran up to speed with LCAs & wheels dangling in the air. LCAs were flopping around quite a bit. I Jammed a crowbar in between the LCA and frame and it died down a bit. The LCA bushings were very sloppy.

I took it to a shop that said it was the right CV axle. They swapped with new OE axle and said it was happy. It is not. Still there.

I swallowed my pride and brought it to the dealer. Worst auto experience of my life. To escape any liability, they refused to listen to me when I said it did it from day 1 and blamed the tires/wheels I put on as well as the subframe which had slight damage from running up on the curb. Basically, all stuff changed months after the vibration was 1st noted.

Out of spite I have gone to the Audi aluminum subframe and a solid rubber LCA lower bushing and it hides the vibration quite a bit with the harsher ride but it’s still there. The car feels like it has a full set of coil-overs just from changing to the solid TT bushing!

So... The car has new aftermarket wheels/Michelin tires, all new OE suspension on the right front, new rotors, pads, wheel bearings (all 4), new OE Right CV axle. The car aligns perfectly. The tires have been road-force balanced a few times and it may help a little but does not eliminate the vibration. Again, the subframe and rear LCA bushings have been changed.

The car has the original left front suspension and CV axle. My local CV shop says they have no way to tell if the axle is bent. I thought they could spin it like a driveline shop does with a prop shaft but they claim no dice. The shaft is so far above the subframe I really doubt anything damaged it. So I really go to worst case scenario and think it’s the output shaft of the diff. Thoughts?

Today I stuck a run-out gauge on the ends of the CV axles but couldn’t get on the joints themselves. Both original and new shafts seem to have about 5 thousands of play on the painted surface at either end of the axle before it goes into the joint. It is likely not a valid test. I also stuck it on the vented edge of the brake rotor and saw about the same number. Again, both new and old look about the same.

So it turns out ATS makes a fantastic NVH test set for finding stuff like this but no one in CO or NM has one. )-:

Any suggestions on next steps? Any shop recommendations in Colorado that has enough of a clue to help? Thanks all. Sorry for the long post. Mikey in Denver.

Man, that’s a tough one. I’d try Hardey’s Motorwerks or Berg Performance. Wife has used Import Mechanics and they’ve done well with her Audis over the past several years. I would not recommend Bluewater.

 

[gixxerfool]

When I was at the dealer we had a three axis scope for identifying NVH source. Made by PicoScope. It was insanely useful when used correctly. You may want to find a shop that has this, or a similar unit, and see what their diag charge is.

More to your question, since it’s been since day one, have you had the transmission evaluated? Could be a bad flywheel launched a weight maybe, or was never balanced in the first place. Possibly a motor or trans mount grounding out, I kind of doubt this since they were moved when you did the subframe replacement.

Since you feel it more in the car and partially in the wheel I would lean more towards chassis/suspension than driveline, but I don’t discount it. You have eliminated all of the common possibilities IMHO, it’s a good idea to start thinking outside the box.

Does the car have LSD? Has that been looked at for any deficiencies?

 

[SVOMikey]

Thanks Superfreak for the recommendations.

Other notes, the vibration only seems to be speed sensitive and not RPM sensitive so I didn't think about a flywheel issue. The car does have the LSD. I have bottle of LSD fluid to change out but haven't done it yet. there's a lot of debate I guess as the service manual doesn't list a maint interval for it.

Another interesting note, the output shaft of the LSD allows the yoke to move in/out a bit and that spoked me. I read a post about someone tightening that up. The dealer did confirm on another car that it seems to be the way they are assembled so I haven't touched it.

Would a tranny shop be able to evaluate the transaxle in the car? Maybe next move is to put it on a lift and measure runout on the output yokes of the tranny? I know my gauge won't fit in there.

I'll defo check into the Picoscope. Thanks Gixxerfool!

 

[xabhax]

Does the vibration go away when it isn't under load, foot off gas and coasting?

 

[SVOMikey]

greatly reduced under coast when not under load but not entirely gone. I'll verify tomorrow when I drive it.

 

[SVOMikey]

Verified but not what I thought. Vibration is consistent under load as well in coast. ~75 to ~80. Gone by 85mph.

 

[xabhax]

You said right axle was replaced. So the left side has never been replaced? Ever used tire sealant? Was the axle used on the right side a good quality one? The aftermarket rims, are you using the correct lug nuts for the wheels? Hub centric rings?

I did this to myself when i put rims on my car. I used the wrong lug nuts and got a wicked vibration.

Only can think of a couple things. Shifted belt in tire, bent rim, wrong lug nuts, something in the tire (Water, sealant), axle.

 

[SVOMikey]

Right axle was replaced with new OE VW. Left has never been replaced. No tire sealant. Vibration was present with the OE wheels as well as the VMR wheels. Good question on the lugs. I'll ask VMR about the crown. There is no no hub spacer on this wheel. It's an exact fit on the hub. I think what I need is a very kind GTI owner on the front range of CO willing to swap wheels for a day and see what happens. I guess there's a chance that the crap tires the dealer put on it to sell as CPO shook as well as the VMR wheels w Michelins.

 

[Superfreak]

Right axle was replaced with new OE VW. Left has never been replaced. No tire sealant. Vibration was present with the OE wheels as well as the VMR wheels. Good question on the lugs. I'll ask VMR about the crown. There is no no hub spacer on this wheel. It's an exact fit on the hub. I think what I need is a very kind GTI owner on the front range of CO willing to swap wheels for a day and see what happens. I guess there's a chance that the crap tires the dealer put on it to sell as CPO shook as well as the VMR wheels w Michelins.

You can come up and grab my track wheels if you want. I have a ‘15r but I’m pretty sure they’d work fine. DM if you want, I’m up near Conifer.

 

[Mike16GTI]

Sounds like something weird, perhaps a tire delaminating or the bands separating. Had this years back with a Golf I had, took forever to figure it out. If you haven't done it, I'd rotate tires from front to back. Maybe perhaps a subtle bend/dent or out of true wheel that can't be seen.