Boxster Autocross Sound

[charles5448]

Hey all,

 

I have a 1999 2.5 Boxster with a 5 speed.

 

I have been auto-crossing the car a few times this summer and started to get the strange noise and vibration out of the car. The noise and vibration only happen during hard cornering while auto-crossing. The tires are brand new and don't show any signs of a rub or making contact with something in the wheel well. When driving the car normally on the street, it rides great with no noise or vibration. I have never had any sort of play with the shift knob in the car and never had any trouble finding a gear. Also I haven't had the 3000 rpm vibration that is associated with a bad motor mount. The transmission mounts look perfect with no signs of leaks. The CV axles look good and aren't torn or ripped.

 

I was starting to wonder if maybe this sound and vibration might have something to do with the Automatic Brake Differential that was an option on this car (Code 222, 224). The car does have the TC button on the dash and it made no difference whether this was on or off during the run. The noise and vibration the car makes almost reminds me of when you are hard on the brakes and ABS kicks in. Once the car is out of the corner everything returns to normal. The little information light that flashes when TC is applied never flashes while it is making the noise and vibration. 

 

If anyone has any knowledge of what this might be, I would be most appreciative. I am still in the early stages of diagnosing the issue so I might be a little vague. I am very happy to provide more information if someone needs it.  I just want to pinpoint if this is normal or not before I go replacing parts!

[ttocs]

First thing that comes to mind is CV joints, along with worn bushings causing extra flexing.

[charles5448]

Would the CV joint give any other indication that they are bad? I have never gotten any noise out of them.

[ttocs]

On a front wheel drive vehicle they often will "click" on left/right turns which stress the joint.

 

Does your noise occur while the car is turning only left, or right, or both?

What is the "frequency" of the sound, how many times per period of time? or once per tire revolution?

 

Check the parking brake. My car was sitting most of the year previous to my purchasing it and the brake drums had some surface rust which caused a loud click sound and felt like a hammer was hitting the wheel a couple times per tire rotation if I pulled the parking brake lever. So I wonder if the shoes might be close enough to the drums such that under high stress and flexing of the suspension that they might be making contact with some rust like what happened with my car.

 

There's also a dust shield that might be touching some wheel hub parts, but I would think that would sound and feel more subtle, less sudden.