is R2 some sort of clutch, i hold it in and it stays in the gear that i am in while using auto tranny, i think its called shift lock, have anyone else tried this?
Well it does 'lock' you in gear, but 'shift lock' in the context of drifting means something else:
Shift Lock Drift
This is performed by letting the revs drop on downshift into a corner and then releasing the clutch to put stress on the driveline to slow the rear tires inducing over steer. This is like pulling the E-brake through a turn, but this should be performed on wet ground to minimize damage to the driveline. (from driftsession.com)
This is basically severe engine braking, to the point of traction loss. GT4 doesn't really have engine braking, so you can't do this.
