My 96 850 GLT wagon has developed what I can only describe as an oscillating high speed vibration. When traveling on the highway at about 70 mph, I get a vibration in the steering wheel that comes and goes at regular cyclic intervals of a few seconds. Kind of like a slow pulsing. It is annoying at best.
No, but I have an idea what physical phenomenon might cause something like that. Generally, when you hear a slow oscillation like that, it is due to what's called a "beat frequency".
click here:
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And scroll down to "Envelope of beat production".
It's like the slowly oscillating drone of a twin-engine turbo-prop plane, caused by the engines running at rpms that are different by, say
10 to 20 rpms.
So, you probably have two rotating elements, each out of balance slightly, that are rotating at nearly the same, but not quite identical rpms. The frequency of the beat is F1-F2. Maybe your two front tires are slightly different in radius (uneven wear, uneven pressure?), and each is a little unbalanced?
Someone with knowledge of typical problems with your model can help from here.
The first thing to try would be to rotate the tires front to back and see if that changes it. Easy to do and would tell you if a tire has developed a problem.
More likely causes would be a bad front wheel bearing or CV joint.
Sure sounds like tire balance. Each front wheel is probably out of balance a similar amount and there is a tiny difference in rolling diameter between them. As you go down the road the forces on the steering alternately add and subtract as the wheels slowly rotate with respect to each other.
A spin balance on the front tires should fix you right up. If a shop in your area uses Hunter balance equipment you can be sure it is done right.
I'd like to thank all of you for your replies. I'm going to have the tires rotated and balanced and see if that solves it. It has been a year or so since that was done so it might not be a bad idea.
I had have similar problems in different car makes (Volvo, Nissan, Silverado, etc.) and in most of times is an uneven wear in tires, as well as small deformations due to impacts, low preassure driving, and such kind of things.
I know that also can be due to high mode vibrations, and if thus it may be ought to a damage or deformation in chassis or body.
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