Failure mode shift pattern alteration for an electronically controlled transmission

Shift pattern control apparatus for a motor vehicle transmission shiftable between successively engageable forward speed ratios including a lowermost speed ratio, an uppermost speed ratio, and one or more intermediate speed ratios, the apparatus comprising:

• electrically alterable memory means having stored therein as a function of speed ratio and driver demand previously determined information corresponding to a vehicle speed at which a transmission shift from said speed ratio should occur;
• look-up means for retrieving previously determined speed information from said memory means pertaining to the current speed ratio and driver demand for comparison with an indication of the actual vehicle speed to schedule shifting from said current speed ratio;
• and
• override means effective in response to the detection of a failure of an intermediate speed ratio for electrically altering the speed information stored in said memory means such that the previously determined information used to schedule shifting between such failed intermediate speed ratio and successively higher and lower speed ratios is replaced with new speed information determined according to an arithmetic combination thereof, whereby further shifting between such successively higher and lower speed ratios is scheduled in accordance with the new speed information.