Grade and payload based transmission gear selection strategy

摘要

A method is described for controlling an automatic transmission of a vehicle during deceleration arising from a force resisting forward movement arising from an incline grade and a vehicle mass. The force of resistance to forward movement is determined at least based upon the incline grade. A destination gear is calculated based upon a set of gear-specific output curves and the force of resistance. The destination gear is compared to a current gear within which the machine is operating. The programmed controller executes an early downshift schedule when the destination gear is at least two positions lower than the current gear, thereby initiating a series of downshifts of the automatic transmission from the current gear to the destination gear. During each gear shift performed according to the early downshift schedule, shifting occurs at a cross-over point between output curves of current and next lower gears.