| | High Speed Vibration
I've experienced an up and down shimmy on the whole dash board assembly where I could feel it on the steering wheel and pedals. It feels as though it's coming from the front end or at least some place under where your feet rest; definitely not from the rear. It happens only in 6th gear at speeds above 70mph. It never shimmies in any other gear at any RPM; only 6th above 70mph. The shimmy itself is a little inconsistent, meaning that it comes and goes at various speeds above 70. However, the vibration unmistakably dissipates upon letting off the gas, and comes back a few seconds after I step on the gas again. I never step on the brake during this whole time, so I don't think it has anything to do with the rotors, especially since the shimmy responds to the throttle/torque.
For those of you who've dealt with this problem or are familiar with it, what are the common causes given the circumstances above?
Any input is greatly appreciated.