car in sig, starts to vibrate bad, as in shake the dash visibly. shifter shaking very badly as well, at about 70-75 mph, maybe even a lil earlier,

so far i' have tried a different driveshaft, difference in vib was minimal if at all,

also this is not a steady vibration, it has a rythm, that is hard to put in words, its sort of on and off, but at a continous rythmic rate.

any suggestions??

 

Check your trans mount.

 

Make sure your tires are still balanced, they can throw the weights off from time to time.

 

i've got one sitting here for it, just gotta do it , i'm inclined to think the mount is not it, i've broken them before, and it never had this vibe. it just felt like the trans was coming to get me when it slammed against the bottom of the car