C5 Vibration

[Bill G]

I have a vibration in the rear of my 2002 C5 coupe (automatic). Background: When I bought the car it had 18K miles on it and the vibration was present then but not as pronounced and it is now at 30K miles. The rear seals were fixed about 5K ago. It has a Blackwing air intake and stock exhaust. Other than that, no other modifications.



Here is how the vibration occurs... If I hold the RPM to just over 3300 in first or second gear and then hold the car steady on a highway, any movement to the rear of the car (side-to-side or a slight dip that causes the rear to react) causes a vibration. This vibration feels like grinding action like a driveshaft bearing is bad. If RPM is higher and the movement to the rear increases (from the road) the vibration gets stronger and louder. A wide open throttle shift from first to second gear will cause it too.



Probably a bad explanation but basically any movement of the rear end with rpm over about 3300 will cause it.



I took the Corvette specialist from the local Chevrolet dealership for a ride and he says that they have spoken with Chevrolet engineers who say it is a harmonic. I doubt that this is the issue. I think something is aligned incorrectly or there is a bearing problem.



Any ideas what it might be?



Thanks - Bill

 

[wishuwerehere82]

Bill,

I would start with the tires first, make sure thay are balanced properly with a Hunter GSP 9700 road force balancing system.
Then work inward and check the rear wheel bearings, CV joints on the axle shafts, and if it doesn't get any better, then the CV joints on the driveshaft.

 

[mrm1149]

Possible Getrag problem, fluid low, needs changed?

 

[Bill G]

The tires were replaced and balanced about 7K miles ago. Am running Michelin Pilot Sport ZP tires.

When Chevrolet replaced the rear seals, the only thing that was not removed in the rear was the transmission. The exhaust was out of it, the suspension, etc. I couldn't believe what they had to do to replace those seals. The car also got the 30K mile maintenence during this time. This includes transmission service.

Nothing changed vibration wise. This is why I suggested that it was a driveline bearing or bent drive shaft. They said it was a harmonic. I am getting ready to take it to a different dealer. By the way, I do have an extended warrenty that paid for the repair.

 

[mqqn]

Hi Bill G -

If it is not a wheel bearing or u-joint (fairly easy thing to check) then I might suspect the torque-tube bushing....just a thought.

http://www.breathlessperformance.com/products/100-504.asp

best regards -

mqqn

 

[Remo]

Bill,

Any late breaking news on the vibration problem?

Remo:cool

 

[Bill G]

Bill,

Any late breaking news on the vibration problem?

Remo:cool

We haven't got it resolved yet. I spoke with Chevrolet and they want to elevate this to a management level at the dealership. If that fails, Chevrolet will help set things up to have it checked by another dealership. I think it is in the driveline between the engine and the transmission. I am still hearing the word "harmonic" from the mechanic and was thinking that this might be a good time to put a Corsa Touring exhaust system on it (just to make sure that there are no harmonics).

Thanks for checking!

 

[gbik]

I had a 1985 camaro with a vibration problem at moderate engine speed. finally found the torque converter was loose on flywheel. Don't know if this helps just my experience. Jay

 

[DRTH VTR]

I am still hearing the word "harmonic" from the mechanic and was thinking that this might be a good time to put a Corsa Touring exhaust system on it (just to make sure that there are no harmonics).

Thanks for checking!

I assume that you are joking D ), but just in case someone misunderstands, harmonics just refers to a vibration that is self-reinforced (sort of a positive feedback). It can be a multiple of the primary vibration frequency, and stuctures can have a frequency at which they like to vibrate. The harmonics associated with an out of balance drive train component have nothing to do with the harmonics associated with exhaust noise.

 

[Bill G]

I am joking up to a point. There is another issue and that is the 1500 rpm rumble that comes from the exhaust system. A Corsa "Indy" or "Touring" exhaust system will fix that.

The main issue is the vibration. The dealership says that they think that it's a harmonic. They told me that Chevrolet engineering have said that harmonics can cause an problem similar to what I have. I think the harmonic theory is nonsense. There is something wrong in the drive train and it reminds me of a drive shaft or u-joint problem.

 

[IH2LOSE]

isnt there supposed to be a large mass installed someplace on the rear of the car to displace this harmonic problem.

Is there a chance it was removed maybee by the previous owner. I had thought when I did my cat back on my 02 there was one installed on my car. I will put my car up on my lift this week and see if I can find it

 

[Bill G]

Thanks for the information!

I took a different mechanic out for a ride today. He says it is a bearing but is not sure where. They are going to tear into it just as soon as the Corsa exhaust gets to the dealership. They have to remove exhaust system to accomplish what they have in mind so I figured they might just as well put the Corsa back on when the time comes. They agreed.