Factors Which Influence the Choice of Gear

Stop and go traffic identification (540iA only)

If the vehicle is driven slowly and only accelerated gently between two stops, the transmission shift program will block the downshift into 1st gear. However, this downshift can be provoked by depressing the accelerator pedal further when the full performance potential of the vehicle is needed.

Downhill gradient identification

AGS identifies that the vehicle is on a downhill gradient when the road speed is increasing even though the accelerator pedal is released. In this situation, upshifts will be suppressed in order that engine braking is utilized more effectively. If the driver also applies the brakes, the transmission downshifts to the next lower gear (RPM permitting) so that engine braking becomes even more effective. If the "Winter" program has been activated, the downshift does NOT occur.

Fast off identification

If the accelerator pedal is eased back suddenly, for instance when the driver transfers his foot to the brake pedal, the shift program prevents an upshift if the transmission is in 3rd, 4th, or 5th gear. This ensures that the available engine braking effect is fully utilized since the driver's action of suddenly easing back on the accelerator pedal is an indication of his intent to slow down the vehicle. This upshift suppression also reduces the number of transmission shifts when the car is driven in a hard or enthusiastic manner, as historically automatic transmissions upshifted to the highest possible gear when the accelerator pedal was released.

Corner identification

Lateral acceleration is computed by evaluating wheel rotation speeds (using the ABS sensor signals). Based on these calculations, upshifts are inhibited when cornering hard to maintain vehicle stability.