This is more of a general GT post than about GT Academy
The feedback from the wheel always goes numb when the car yaws too much in GT 5 and GT Academy, generally noticeable while in a "tank slapper" or while drifting. Well, I finally found out why and it has nothing to do with the GT Simulation! (If this is already widely known please let me know)
Usually in LFS or any other PC sim, the simulation dictates the force feedback. For those whom use Logitech wheels there is an added steering effect, "centering spring" which forces the wheel to center. While messing around with the Logitech Profiler I wanted to see what centering spring force felt like. I moved the slider to 100% and started LFS, particularly to try drifting. Imediatly LFS felt just as bad as GT 5. The force feedback would just dissipate as the car yawed more until there was no feedback at all.
What happened in LFS is exactly what happens in Gran Turismo. I speculate that the feedback force starts to equalize with the centering spring force causing a net 0 force out of the electric motors. Try it for your self.
BTW: LFS feels much better while straight line driving with centering spring force on. Just need to find the medium where it is not too strong that it cancels out the force feedback.