Large Vibration at ONLY 65mph
03-27-2008, 02:12 AM
#1
Large Vibration at ONLY 65mph I know what to check for almost all vibrations. I've searched a lot. However most have to do with general vibrations. Mine ONLY occurs at 65mph (and 3-4mph on each side of it) and then goes away below or above that speed. It just really sucks because that is my main highway speed.
Car as 30k on it. Stock suspension. Poly trans mount.
The poly mount didn't make it more noticeable, but didnt help. It is just that it is hardcore at that 65mph. Car jumps up and down like a horse. Other than that is is smooth sailing, which is weird.
The two things I've checked are wheel balancing (recently got new wheels and nothing changed at all btw) and the U joints are perfect. How do I check for a bend driveshaft? (Even though it seems this may not be it.)
What else would make a precise vibration like this?
Car as 30k on it. Stock suspension. Poly trans mount.
The poly mount didn't make it more noticeable, but didnt help. It is just that it is hardcore at that 65mph. Car jumps up and down like a horse. Other than that is is smooth sailing, which is weird.
The two things I've checked are wheel balancing (recently got new wheels and nothing changed at all btw) and the U joints are perfect. How do I check for a bend driveshaft? (Even though it seems this may not be it.)
What else would make a precise vibration like this?
03-27-2008, 02:16 AM
#2
you changed you clutch recently, ive heard of people getting bad vib. from flywheel PP. but its weird it only does it at 65 mph. i would say maybe wheel bal. but you said you already had this checked
03-27-2008, 02:31 AM
#3
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My car does this as well. 65-70ish it vibrates throughout the car. But doesn't when it's lower, and doesn't when it's higher. Someone mentioned that that its drivetrain vibration.
I recently had tires mounted and balanced, so it's definitely not a balance issue.
I recently had tires mounted and balanced, so it's definitely not a balance issue.
03-27-2008, 07:48 AM
#4
same deal for me, but 70-75ish mph. feels like its right around 1600-1700 rpms
03-27-2008, 09:58 AM
#7
Does the vibration occur at 65mph in every gear? If the vibration follows rpm, the cause is in front of the transmission. If it follows speed, it's behind the trans. If it is in fact a "speed" vibration, take your driveshaft to a shop that can balance it. They'll be able to tell you if it's bent or out of balance. If that doesn't cure the vibration, you need to check your pinion angle. You may have a bent torque arm throwing everything out of whack. Even minute misalignments in pinion angles can cause wicked vibrations.
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03-27-2008, 07:33 PM
#8
Does the vibration occur at 65mph in every gear? If the vibration follows rpm, the cause is in front of the transmission. If it follows speed, it's behind the trans. If it is in fact a "speed" vibration, take your driveshaft to a shop that can balance it. They'll be able to tell you if it's bent or out of balance. If that doesn't cure the vibration, you need to check your pinion angle. You may have a bent torque arm throwing everything out of whack. Even minute misalignments in pinion angles can cause wicked vibrations.
Interesting you brought up the torque arm, as whenever I go over a bump in the rear (when the rear end is pushed upwards (like if you were to lower a car) I hear drivetrain noise. I think my pinion angle is off (I'll be soon getting a adj. torque arm with my full suspension here soon.)
And I BELIEVE it is entirely speed related, as it did it in both 5th and 6th gears, but it has been a while since I "tested" around with it. Once I get back home I'll go on the highway and make sure, and report back to you guys, as well as giving updates to what is or is not the issue.
03-28-2008, 08:59 AM
#10
Do you still have your stock suspension?
I've had the same issue since my car (a '99 WS6) was delivered from the factory. I chalked up the phenomenon to the car's natural frequency and my solution was to just hammer-down to 69 or 69 mph. (One thing to remember is that when these cars were designed, highways were just starting to consistently go up to 65mph across the country!)
Last year, I installed SLP shocks and haven't noticed the vibration since.
I've had the same issue since my car (a '99 WS6) was delivered from the factory. I chalked up the phenomenon to the car's natural frequency and my solution was to just hammer-down to 69 or 69 mph. (One thing to remember is that when these cars were designed, highways were just starting to consistently go up to 65mph across the country!)
Last year, I installed SLP shocks and haven't noticed the vibration since.
03-31-2008, 04:24 PM
#14
A localized vibe is almost always driveline. It's probably the driveshaft. If it's the steel driveshaft, it's almost definitely the driveshaft. Poly mount doesn't absorb vibes like rubber. Changing didn't cause the vibe but revealed it. Change to aluminum shaft. If that doesn't work, put the rubber mount back in.
This is your most likely cause.
Other unlikely causes:
Tires
Shocks
This is your most likely cause.
Other unlikely causes:
Tires
Shocks
09-21-2008, 09:25 PM
#15
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I feel your pain. I have had that vibration with both the stock rear end and my 9". With a stock torque arm and an aftermarket one. A new u joint and old u-joint. I think there is vibration in the tailshaft housing somewhere because the I know the drive shaft isnt bent and was just balanced. I'll live with it because I set my cruise @ 66 and let her be right it off as the nature of the beast kinda thing.
