OK, This is not a *Contour* experience, since I've only had my SVT for about two months now.
I had a bad motor mount on my 86 Maxima SE. What I experienced on this was, when there was a sudden change in drivetrain torque (i.e. the clutch let off or engaged), there was a heavy, muffled *thunk* noise up front. The engine/tranny was rocking back and forth very slightly, I suppose.