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Vibration when accelerating

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Vibration when accelerating

  #1  
Old 05-23-2011, 12:15 PM
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Default Vibration when accelerating

My 2004 Audi A8L (now at 97k miles) vibrates when accelerating normally, it smoothes out after the car has built up good speed but if I try to accelerate again near 70 to 80, the virbation starts again. I recently noticed this after I had my back tires changed on Friday, but I can't see why that would make the car vibrate.

The transmission works normally and shifts normally, its just the vibration that seems to be in the center of the car when driving straight forward.

Any suggestions? Thanks.
 
  #2  
Old 05-23-2011, 02:26 PM
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Originally Posted by A84ADATE View Post
I recently noticed this after I had my back tires changed on Friday, but I can't see why that would make the car vibrate.
If it wasn't there before, the odds I'd give it are:

70% - tire(s) not balanced properly
20% - alignment required
10% - other or bad tire(s) which is unlikely
 
  #3  
Old 05-23-2011, 11:12 PM
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Need to watch closely if the vibration happens at same rpms, regardless of car speed..or just during acceleration and STILL look at rpms.
 
  #4  
Old 05-24-2011, 09:13 AM
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i know its not the tires, it only does it when I push the accelerator if i let off, its smooth.

I sure its time to replace the rear right and left CV because when I turn at low speed sharp, I can feel the grind/vibration which is similar to what I feel when I am pulling forward.
 
  #5  
Old 05-24-2011, 10:25 AM
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IN general CV's do NOT wear out...bullet proof...with boots and grease in place, they'll go at least 1/4 million miles.
They do not grind in corners..if dry of grease (boots ripped open) for many miles, they pop/click.

If hearing/feeling grinding in rear in corners, classic wheel bearing noise...also NOT a normal wear item (but much more likely than CV failure), unless running excessive incorrect wheel offset for long periods.

Bad tires can produce symptoms that people don't believe until they're solved...even expensive tires. Bad alignment alone can produce grinding feel in low speed corners...if off just enough, a front tire can be "shoving" (plowing), rather than rolling smoothly, causing sometimes intense vibration.

CV's are often the most misdiagnosed NON-problem, esp when one has never had one go bad...their symptoms are unique and nothing like the grinding/squealing of failed bearings or defective tires.

Inner front CV's (actually triple roller joints) if badly failed (no reason, without dry lube or actual impact) , could cause vibration on hard acceleration..but not a common problem.
 

Last edited by silverd2; 05-24-2011 at 10:28 AM.
  #6  
Old 05-25-2011, 10:19 AM
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Originally Posted by silverd2 View Post
IN general CV's do NOT wear out...bullet proof...with boots and grease in place, they'll go at least 1/4 million miles.
They do not grind in corners..if dry of grease (boots ripped open) for many miles, they pop/click.

If hearing/feeling grinding in rear in corners, classic wheel bearing noise...also NOT a normal wear item (but much more likely than CV failure), unless running excessive incorrect wheel offset for long periods.

Bad tires can produce symptoms that people don't believe until they're solved...even expensive tires. Bad alignment alone can produce grinding feel in low speed corners...if off just enough, a front tire can be "shoving" (plowing), rather than rolling smoothly, causing sometimes intense vibration.

CV's are often the most misdiagnosed NON-problem, esp when one has never had one go bad...their symptoms are unique and nothing like the grinding/squealing of failed bearings or defective tires.

Inner front CV's (actually triple roller joints) if badly failed (no reason, without dry lube or actual impact) , could cause vibration on hard acceleration..but not a common problem.
Ok. thanks for the info silverd2, I guess I will take it in and have technician look at it.
 
  #7  
Old 03-16-2012, 12:00 AM
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Did you ever find the problem? Mine is doing the same exact thing.
 
  #8  
Old 03-16-2012, 09:57 AM
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Originally Posted by greekengreg View Post
Did you ever find the problem? Mine is doing the same exact thing.
Good Morning,

I found out that the tires I had on the back 275/40/19 (Conti) which may have been too tall, because they appeared taller compared to the front 255/40/19 (Conti Contact 2) was causing the quattro to go hay wire, this was after spending over $1400 trying to figure it out what was wrong. Audi told me it I need a new rear diff over $3400, so I found a used one with 39k mile had it repalced and the same problem remained. I finally found a good VW/ Audi A8 tech...he told me the rear tires may not be recognized by the quattro system...I put my other 255's back on, problems went away instantly. Those Audi Dealer guys SCREWED me 2 times...first telling me I need spend $3400 and then had an issue with MMI and said I need to have MMI motor replaced for $600.

Well I hope this helps your problem.
 
  #9  
Old 03-16-2012, 06:31 PM
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On all cars with AWD, it is extremely important that the rolling diameter of the tires are the same. The tires that were listed above for the rear are larger/ taller [ i.e., a greater rolling diameter from the front tires] ) so the AWD gearing is fighting itself and will wear the transfer case gears quickly as well as make some odd noises. The dealership should have caught that mistake in sizing the front to rear tires that were used.
 
  #10  
Old 03-19-2012, 10:31 AM
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Originally Posted by MNNYA View Post
On all cars with AWD, it is extremely important that the rolling diameter of the tires are the same. The tires that were listed above for the rear are larger/ taller [ i.e., a greater rolling diameter from the front tires] ) so the AWD gearing is fighting itself and will wear the transfer case gears quickly as well as make some odd noises. The dealership should have caught that mistake in sizing the front to rear tires that were used.

i figured with the tires both being "40" i didnt think it would have been a problem but come to find out, with it being a different continental tire model than the front, it must have been a little taller, I have had 275's on the back before with no problem. Thanks.
 

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