Front end vibration between 65 an 80 mph. need help diag.

[Camel]

Here is the problem and the soluitons that I have tried:

Problem:

Front end vibrates under acceleration and cruising between the speeds of 65 and 80 mph. Vibration planes out after 80 mph to a slight (very slight) shake. Deceleration, the vibration is less pronounced.

Not RPM related at all. Only under load and between these speeds.

Solutions tried:

New TC Rod Bushings.-Replaced the goo oozing bushings with urethane ones from PDM.

Four wheel alignment.-Alignment seemed to help at first. But upon further driving, I realized that the problem occurs at a slightly higher mph than before. Now placing itself between 72 mph and 80 mph.

The tires are good and not flat spotted at all. The car is driven daily.

The only things that I can figure are: maybe blown struts in the front, bad control arm bushings, or tie rod ends (but the car tracks properly and there is not slop in the steering at all.)

NISTECH, help me out here if you can. One thing I would like to know is how to identify blown struts.

[Checkered-Member]

Might be wheel balance, are you sure you haven’t lost any weights?

[Camel]

Pretty sure. No clean spots on my dirty factory rims. I would think that would show up at more speeds than just what I am seeing.

[Rex]

If you're running the same size tires all around, swap them from front to back or left to right to see if it makes an difference, if it's a wheel/balance isue and you move the wheel with an issue to or from the front you should feel a difference in the steering wheel.

Another thought, does the vibration maintain (as long as speed does) if you get to that speed and "coast". That could let you know if it's coming from the motor?? Recently, a Q owner found underspray/road tar on his drive shaft that was causing a slight vibration.

Good luck.

[Checkered-Member]

Another thought, does the vibration maintain (as long as speed does) if you get to that speed and "coast". That could let you know if it's coming from the motor?? Recently, a Q owner found underspray/road tar on his drive shaft that was causing a slight vibration.

Good luck.

But he said it isn’t rpm related…you would think there will be more vibration at higher rpm if it was engine related...my logic

[Camel]

I think what he is saying is that it may be driveline related rather than engine related. I don't think that it is engine related, but a driveline related problem could be the case. Regardless of that, I think that I will take the suggestion about the tire/wheel rotation to eliminate variables before I go spend money on balancing. That is a great suggestion, thank you very much. I will report back tomorrow with results.

I still would like to know how to identify blown struts though. The car handles well but i need a good excuse to spend some cash on a set of KYB's and springs.

Thanks for the great help guys (and in short order i might add). Again, I will report back tomorrow after swapping the fronts to the back.

If the prolem contines, I will try the coasting method to check the driveline (I believe that it does still happen when coasting down from 80 to 60. I get the shimmy somewhere in between.

C

[NISTECH]

I have to agree . It seems you have a tire imbalance issue. to tell if you have bad stuts they either make a rapid knock noise when driving over uneven road surfaces(asphalt cracks) also when jouncing the car it should imediatly return to rest position when you let go. no repetitive osillations trying to find center.

[Camel]

So the tire rotation thing should be a really good test, right?

And on the strut thing, thanks for the info. I figured if it looked like a bobblehead doll, it is time to replce the struts. Oh well, no TEINs for me, YET...

[NISTECH]

yea you will most likely still feel the vibration but it will have different charicteristics when in the rear.

[Camel]

Thanks, I am going to try it tomorrow.

[Camel]

Ok, swapped the wheels front to back today. Made a huge difference. I am going to take this thing to get all 4 tires speed-balanced later this week.

Thanks for all of your help guys.

[Rex]

Glad to hear that helped, could have been some "crude" on the indise of a rim that was dislodged during the swap.

[Camel]

Don't think so, I drove highway today and felt a little vibe from the rear of the car. Need to get all four balnced for safety's sake.

[Camel]

It was a tire that was out of round. I got new tires and the problem went away completely.