In fact, what is really impressive about the EMD class is that the wheel slipping can actually be controlled using radar that senses the linear speed of the loco which is taken as the reference for comparison. In other locos, during slip, corrective action is taken (like reducing current supplied to the motors) for re-adhesion.
Hence, the uncontrolled spin of the wheels is prevented in EMD's. Sanding is automatically invoked whenever an axle slips.
GM's technology after all _/\_