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LESSON 3: POWERTRAIN
Shift Patterns
•
Under certain conditions the transmission automatically downshifts to a lower gear range (without moving the
range selector lever). There are three categories of automatic downshifts:
– coastdown
– torque demand
– forced or kickdown shifts
•
Coastdown
The coastdown downshift occurs when the vehicle is coasting to a stop.
•
Torque Demand
The torque demand downshift occurs (automatically) during part throttle acceleration when the demand for torque
is greater than the engine can provide at that gear ratio. If applied, the transmission will disengage the Torque
Converter Clutch (TCC) to provide added acceleration.
•
Kickdown
For maximum acceleration, the driver can force a downshift by pressing the accelerator pedal to the floor. A
forced downshift into a lower gear is possible below calibrated speeds. Specifications for downshift speeds are
subject to variations due to tire size, engine and transmission calibration requirements.
2005 Expedition/Navigator New Model Technician Training02-SEP-043-46