[Christ]

Originally Posted by MechEngVT

Is the Audi TT? The Volkswagen New Beetle? Both are FWD, but both have suffered from high speed instability due to aerodynamic lift at the rear.

In high-speed highway driving (and no, 80 mph doesn't count...I'm thinking Autobahn counts) rear downforce improves stability regardless of drive configuration. A stable vehicle is one that is slightly biased toward understeer. Having a front engine or front weight bias when combined with rear lift will make a vehicle more prone to oversteer. A little bit of oversteer at 125 mph during a lane change can be fatal. Oversteer is always unstable (when not throttle-induced). At high speeds during emergency maneuvers it can happen fast enough that no human driver can correct the steering quickly enough to catch it without going into oscillations. This is why every vehicle in mass production has varying degrees of tendency to understeer.

2000mc and lunarhighway are right; check rear for toe-in and replace old bushings, ball joints, and bearings. Any slop in bushings/joints can cause dynamic toe-out at the non-driven axle as the vehicle is pulled forward but the loose suspension lags behind. The opposite (dynamic toe-in) will happen during driving at the driven axle, but during braking a sloppy driven axle will transition to dynamic toe-out and make the car feel unstable during hard braking.

You sure about that? I might be wrong, but I'm fairly certain that dynamic toe settings move outward as you speed up.