1996 Mercury Grand Marquis Owner's Manual - Page 178

When to use j (Overdrive) Overdrive is the usual driving position for an automatic overdrive transmission. It works the same way Drive works, automatically upshifting or downshifting as the vehicle speeds or slows. 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 j (Overdrive) - with Transmission Control Switch activated (TCS) 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, press the TCS located on the shift lever. You can depress the TCS 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. 175