Torque converter slip rate based skip power downshift control strategy

摘要

A power downshift control method/system strategy (FIG. 6), based upon sensed torque converter slip (TC slip) is provided for an automated mechanical transmission system (12) including an engine (16), a mechanical transmission (14) and a torque converter (20) drivingly interposed the engine and transmission. At the beginning of a power downshift, the target gear is derived from the TC.sub.-- slip, vehicle deceleration, current gear and operator throttle demand. These four vehicle conditions are parameters of a four dimensional matrix such that increasing values of each parameter promote a greater potential for skip power downshifting.