Car Vibration Diagnosis

ford
mustang

#1

[2000 Ford Mustang 3.8L V6 AutoTrans]

I’ve looked all over the internet and haven’t been able to find someone describe a vibration like mine. My vibration is different in different gears. First and Second gear are vibration-free. Third gear has a vibration that pulses between horrible and barely noticeable at the rate of about once per second, and this rate speeds up to about 4 times per second as my rpm increases (although every once in a while, maybe one time a week, I will have a perfectly smooth 3rd gear). Fourth gear has a noticeable vibration which gets worse with increase in rpm.

This vibration is felt in mostly the seats, and very well heard in the change sitting in my cupholder. I’ve gone through an alignment, brake pads, and tires since getting the car and the vibration didn’t seem to change with any of them. Any suggestions?


#2

Mine had the same problem (4.6 V8 and auto trans) and finally discovered the driveshaft was 2.2 oz out of balance.