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Violent vibration coming from where?

Old 09-06-2011, 12:16 PM
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lanceccs
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Default Violent vibration coming from where?

My car is built for track, thus I put in all the solid or hard bushings. From engine mount, trans mount, diff mount, arms bushing and subframe bushings. Almost all bushing on car has been replaced. Don't flame because it is built for track and NVH is ok.

My car has this short burst of violent vibration, I am trying to find out where it is coming from.

When I was on stock clutch, the behaviour was that when deaccelerating from high RPM (6000 RPM), the car will go thru a short burst of sudden and violent vibration, usually at around 5000 to 4000 RPM.

Recently, I've just replaced my clutch with SPEC Super Twin and the vibration became milder and shifted from 2000 to 2500 RPM when accelerating. Also noticed that the rear (trunk) is also vibrating this time.


I suspect this has to do with....
Bushings, yes I know. But why only specific RPM when the violent vibration occurs? Is it because some rotating part is not well balanced thus at a certain rotating speed it spins out of balance causing the violent vibration? This has to be from the drivetran as when I rev the car in netural, it is not happening.

So what could it be? Flywheel, Clutch, Driveshaft, Diff?

Anyone? Would appreciate your input. Thanks.
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Old 09-06-2011, 12:19 PM
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I don't know
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Old 09-06-2011, 12:54 PM
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I get the decel vibration at times (short burst felt thru the shifter). Doesn't happen all the time... Not sure what it is, almost feels like 1 cylinder firing for a brief moment.
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Old 09-06-2011, 01:03 PM
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lanceccs
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Originally Posted by djamps View Post
I get the decel vibration at times (short burst felt thru the shifter). Doesn't happen all the time... Not sure what it is, almost feels like 1 cylinder firing for a brief moment.
Mine is felt thru out the chassis. From engine bay to the trunk. The whole chasis is shaking...and it happens all the time at the said RPMs
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Old 09-06-2011, 01:35 PM
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I experienced this yesterday and today during heavy rain. It was when I left off the gas aroun 3k Rpms it would start vibrating and sounded like it was about to blow up. Drove it after it rained and now everything is fine. Wtf?
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Old 09-06-2011, 01:44 PM
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If the vibration happens in several gears (first, second, third, maybe fourth) at the same engine speed range (4-5K rpm), it's probably something in the engine, clutch or transmission input shaft.

If it only happens in one gear at that engine speed range, it's likely to be further back in the drive train.

Does the vibration stop immediately when you depress the clutch pedal?

Have you tried rotating your driveshaft with respect to the transmission output shaft and/or the differential input shaft?

Have you checked the runout and/or balance of the driveshaft?
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Old 09-06-2011, 01:55 PM
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lanceccs
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Its happens in specific RPM, not a specific gear. I suspect driveshaft...let me try depress the clutch when its vibrating, this will isolate it between engine or drivetrain issue.... I think should be easy to troubleshoot since it comes on without fail every 2000 to 2500 rpm...

Originally Posted by winchman View Post
If the vibration happens in several gears (first, second, third, maybe fourth) at the same engine speed range (4-5K rpm), it's probably something in the engine, clutch or transmission input shaft.

If it only happens in one gear at that engine speed range, it's likely to be further back in the drive train.

Does the vibration stop immediately when you depress the clutch pedal?

Have you tried rotating your driveshaft with respect to the transmission output shaft and/or the differential input shaft?

Have you checked the runout and/or balance of the driveshaft?
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Old 09-12-2012, 12:19 PM
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I also have a violent vibration in my shifter. I have the touring (so yes admitting to having an auotmatic) I just got new tires and alignment but it seems when I pick up speeds around 75+ and really give it extra gas that my shifter will start rattling forward and backward (not taking it out of gear) but still to the point where some of my passengers have asked about it with concern. I haven't had much luck finding anyone else who has this problem.
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