Well, I got my rx7 yesterday, and i noticed something wrong with the car. As i take the car to higher speeds such as 60mph there is a wobble in the rear end, not in the corners, but on straight road, at this speed its only really noticable if you go over a bump, however, at 100mph the car shakes so violently that i won't dare to take it to 110, it feels almost as though i'm turning left and right very quickly. I've read about the DTTS system and i was able to feel that in the corners and i like it, but the feeling that i described above is completely different and not enjoyable or beneficial at all. Can anyone tell me what it could be??

 

Something is loose.

Check that all lugnuts are tight.
Do a visual inspection of the bushings.
Loosen and torque major nuts and bolts.
Apply a load to bushings and see if any flex too
easily.

Good luck.

 

Driveshaft! Check the driveshaft