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Vibration when foot off throttle between 70-75 MPH only

11K views 22 replies 10 participants last post by  doji_nj 
#1 ·
The last 2-3 days, I have started getting this horrible vibration all over the car when I take my foot completely off the accelerator around 70-75 MPH. As soon as I gently tap the brakes when the vibrating starts or push the gas pedal to accelerate, the vibration disappears. So I have learnt to drive without taking the foot off the pedal suddenly at highway speeds, which is not easy in rush hour traffic :)

Is a wheel balancing and alignment required? Or is there a chance there is some thing in the front-end suspension that is out of whack and might need to be replaced? My tires (Bridgestone Potenza 960 Pole Position) have 10K miles on them and I do primarily highway miles.

I did have new front pads and rotors put on a week ago. Another incident was that I hit an undulation in the road (no pothole) around 10 days ago at 50 MPH and thinking something might have screwed up the right passenger side after that? The car handled fine after the bump and no vibrations but am wondering if an incident like this might take a week or two before the vibration shows up?

I was planning to go to Firestone for an alignment and wheel balancing /rotation but wondering if that will fix the problem, or do I have a bigger problem with the car?
 
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#12 ·
Yeah I am thinking clutch too!! Can't be axle or wheel related as it would get worse as you go faster not just at one specific speed. It may be that when you let go of the throttle the torque converter is not engaging properly and switching the gears. You have been using the proper tranny fluid right!?
 
#13 · (Edited)
Yes I am. Infact, I just did a drain and fill a month back of SPIII fluid. So looks like this entails a trip to the dealer to fix the torque converter. What financial damage am I looking at for this problem? :D

I am able to create this vibration at will. As in only between 70-75 MPH when I let my foot off the gas completely does the vibration appear and pretty much through the entire car for 2 to 5 seconds, and goes away if I step on the gas right away. As of now, I drive like I have an egg between my foot and pedal so that the shudder does not appear when decelerating.

I plan to take the car for a tire rotation and alignment anyway since I'm due for it. If the vibration remains after this, I have no choice but to take it to the dealer and have them figure it out.
 
#14 ·
I have that problem too but I know mine is because I need new half shafts cause my boots broke. When I just changed my brakes I was able to chake the rotor and not have the steering wheel move.
 
#15 ·
if you are having your wheels/tires balanced for car-shaking problems, get them ROAD FORCE balanced. Not just static balance. Road Force. If the tire guy looks @ you like you are dumb or tries to hem & haw just find another shop.

Note: if it only happens >70, how about trying <69 until you get it fixed?
 
#16 ·
a static balance is just with the weights on the inside of the wheel. A dynamic balance has weights on both the inside and outside and can be done on a normal non-road force balancer. A road force balancer is different because it simulates the effects of driving and gives you a number corresponding to how well it does.

A tire can be perfectly balanced but still fail a road forcer.
 
#18 ·
I had Firestone do a wheel alignment today. The vibration has reduced slightly, but they did a road test and confirmed that there is something either with the transmission or axle that is causing this vibration that they prefer not to get into, and referred me to a local transmission shop.

The vibration is now very pronounced when I am going slightly uphill between 70-75 MPH on a gradual left to right turn and I need to slow down to reduce the vibration. So the vibration has progressed beyond appearing only when suddenly off the pedal when at highway speeds.

Looks like a trip to a Hyundai dealer in central NJ is in store soon to figure out this issue. Also, is there a chance that 'if' I migh have overfilled the tranny fluid by perhaps quarter a quart of SPIII that this issue might have arisen? Is the TCM very sensitive to fluid level?
 
#19 ·
If there is none, it won't run. If there is way too much it wouldn't be good but an extra dribble won't kill anything but your paint.

Did they road force balance the tires?

Before you go spending a zillion dollars at the dealership, try this: Rotate the tires front to back, and see if it changes. If it changes, or goes away it's the tires or wheels.
 
#20 ·
When you're accelerating, more of the weight is on the back tires, and when you decelerate/brake it shift to the front tires again. Not a huge difference, but it might matter. Rotating the tires is one way to experiment with just changing one thing. What about using "3" instead of "D"? Does it still happen? Does the vibration stop if you shift into Neutral? (not a trivial thing to try at 75mph)
 
#21 · (Edited)
Tried shifting to neutral when the shudder was quite pronounced under mild acceleration at highway speeds. The vibration remained while in neutral. So that pretty much should rule out any tranny issue?

So it is the axles that is causing the problem. DJHellfire, thanks a ton for your help!!
 
#22 ·
Replaced both front car axles today. Haven't had a chance to drive at high speed as yet and see if replacing the axles solves the shuddering when acelerating.

Also need to add another 1 quart of SPIII and then take the car for an alignment.
 
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