Ford 2003 Mustang Workshop Manual page 2267

Apply and release of the torque converter clutch.
Maximum fuel economy during normal operation.
Second Position
This position provides:
Second gear start and hold.
The torque converter clutch can apply and release.
Improved traction and engine braking on slippery roads.
Engine braking for descending steep grades.
First Position
If this position is selected at normal road speeds, the transmission will shift into second gear, then into
first when the vehicle reaches a speed below approximately 45 km/h (28 mph).
This position provides:
First gear operation only.
Engine braking for descending steep grades.