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Volkswagen Jetta, Golf, GTI: 1993-1999, Cabrio 1995-2002 (A3) Help IDing The Cause of A Front End Vibration


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Last Post: Nov 18, 2013 1:11 PM Last Post By: BobD
Gene54

Posts: 169
Registered: 06/24/04
Help IDing The Cause of A Front End Vibration
Posted: Oct 30, 2013 8:44 PM
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The next problem I'm chasing is a high frequency vibration I feel in the powertrain and steering wheel. Its not a thumping, shake or shimmy like you'd feel if a wheel is bent or out of balence, but a higher frequency. I had a local shop check and confirm the front tires aren't out of balance, so that should rule that out. Normally I'd start having a look at the axles and CVs, but they've been replaced in the last month or so, with the correct types including the tublular rather than solid passenger side.

That leave's one or more bad engine mounts or the front bearings. The front bearings seem to be nice and quiet with no growling when you steer the car in either direction. I've noticed while I was checking for TDC, when I rocked the car in gear to move the crankshaft, the motor rocked a bit. Not a huge amount but enough that it can be seen and you can feel the movment on the front motor mount. I did the standard in gear and engage the clutch with my other foot on the brakes and the hand brake on. The motor moved a little, but not the jump you'd expect if a mount was gone.

Should there be any movement in the front motor mount or does the movement indicate it needs replacing? If it not the mount, can the front bearings be bad even though they aren't making any noise? Or is there another cause I should be checking for?
RickW

Posts: 718
Registered: 02/16/05
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 1, 2013 8:58 AM   in response to: Gene54 in response to: Gene54
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Hello, Gene

I'm not sure what to tell you about the motor mounts, but I've had wheel bearings go bad before, and have almost never had the classic symptoms you describe. I had a set go bad once, but the noise was unaffected by steering, and only changed with road speed.

A good way to check the front wheel bearings is to raise the front of the car off the ground and support it safely on jack stands. Then, grab each of the front wheels at 12 o'clock and 6 o'clock and rock it. Any noticeable play probably indicates a worn wheel bearing. If the wheel is solid at 12 and 6, but moves if you grab it at 9 o'clock and 3 o'clock, then you probably have wear in some of the suspension and steering components.

Rick W,
Bentley Publishers
Gene54

Posts: 169
Registered: 06/24/04
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 1, 2013 7:21 PM   in response to: RickW in response to: RickW
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It all got a more interesting this afternoon.

I decided to check the new passenger side axle, so I loosened up the six bolts to the inner CV and it fell apart!! My undergrad in Mech Eng so I ended up on a conferance call with two of the supplier's engineers who said the symptoms sounded like there were some miss matched parts in the CV. They claim I'll have a replacment by Wed or Thur.
RickW

Posts: 718
Registered: 02/16/05
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 4, 2013 7:46 AM   in response to: Gene54 in response to: Gene54
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Sounds like you found the source of the problem. Best of luck with the repair and thanks for the update.

Rick W
Bentley Publishers
Gene54

Posts: 169
Registered: 06/24/04
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 6, 2013 1:46 PM   in response to: RickW in response to: RickW
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Attachment Chart.JPG (18.8 KB)
Attachment Axle.JPG (16.6 KB)
Just got word I'll have the replacement axle tomorrow
morning. The supplier tells me it’s is going to be identical to the OEM part,
hollow shaft and including the vibration damper like what was on the original
axle. Since this is a MK3.5, Cabrio, anything that contributes to controlling
chassis and drive train vibrations has got to be a good thing.

I’d like to completely check out the axle before it
installed and that includes the location of the damper. Researching this
problem I found a picture of a passenger side axle with axle vibration damper
hitting the metal block vibration damper bolted to the sub frame. I’d like to
avoid that problem!! I found these charts of where the damper is supposed to be
located along the length of the axle. Does anybody here know if the data shown
is also applicable to a 2001, Cabrio?


Thanks


Gene

Edited by: Gene54 on Nov 6, 2013 1:46 PM

Gene54

Posts: 169
Registered: 06/24/04
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 7, 2013 2:04 PM   in response to: Gene54 in response to: Gene54
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Attachment 1107131051.jpg (295.6 KB)
Attachment 1107131050a.jpg (299.0 KB)
Attachment 1107131050.jpg (334.6 KB)
Thought I'd post a few pictures of the axle they sent. After reading all the posts regarding vibration problems with the rebuilt axles that are missing the damper, I thought the members might be intetrested that you can get them. I also noticed while I was refitting the vibration damper block on the cross member there's a bevel machined on the edge that faces the axle vibration damper.

If anybody's interested I'll be glad to forward the source, their customer tech and engineers were absolutely first class, and a pleasure to deal with.

Gene
BobD

Posts: 1,833
Registered: 11/29/04
Re: Help IDing The Cause of A Front End Vibration
Posted: Nov 18, 2013 1:11 PM   in response to: Gene54 in response to: Gene54
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