A method of operating an automatic transmission.

摘要

An improved shift pattern control in which successive upshifting and downshifting is avoided in conditions of above normal loading by inhibiting upshifting to a speed ratio having insufficient gradeability in relation to a measure of the actual loading. In essence, the control continually monitors the gradeability of the various forward speed ratios of the automatic transmission in relation to a measure of the actual grade load to determine their excess gradeability, and removes from the shift pattern those speed ratios having insufficient excess gradeability. This ensures that the automatic transmission will never be upshifted to a speed ratio that has insufficient gradeability for the given driving condition, thereby eliminating the successive upshifting and downshifting which occurs with conventional shift controls.