1996 Ford Mustang Owner's Manual - Page 177

However, Overdrive also shifts into a fourth gear -an overdrive gear - when your vehicle cruises at an appropriate consistent speed for any length of time. This fourth gear will increase your fuel economy when you travel at cruising speeds. When to use D (Overdrive) - with transmission control switch activated (O/D OFF light illuminated) Overdrive may not be appropriate for certain terrain. If the transmission shifts back and forth between Third and Fourth gears while you are driving on hilly roads or if your vehicle does not have adequate power for climbing hills, depress the TCS. You can depress the TCS marked "OD" at any speed. When to use 2 (Second) Use 2 (Second) for start-up on slippery roads or to give you more engine braking to slow your vehicle on downgrades. When to use 1 (Low) Use 1 (Low) when driving down steep grades. It gives more engine braking to slow your vehicle than 2 (Second) on the downgrades. You can upshift from 1 (Low) to 2 (Second) or from 1 (Low) to Overdrive at any speed. P (Park) Always come to a complete stop before you shift into P (Park). Make sure that the gearshift is securely latched in P (Park). This locks the transmission and prevents the rear wheels from rotating. 181