When I am on the freeway or even at 35 mph i am getting a vibration. it seems to be related to speed, not rpm. I assume that rules out the tranny. I have heard it is likely my pinion bearings. is there any other test that can be done to distinguish/rule out tire wear, driveline, pinion bearing or any other possible root to this problem. I suspect that my gear ratio may be too high also. Would this cause vibration problems as well? thanks.