A shift control and shift strategy for an automatic transmission in an automotive vehicle driveline wherein the automatic ratio shift schedule can be disabled selectively to accommodate a manual ratio shift control. A driver-operated mode selection switch permits the operator to select normal automatic ratio control or a launch-assist mode during operation in the normal ratio shift mode. Ratio changes occur in response to driveline operating variables in a vehicle launch-assist mode. The transmission control system is commanded to effect a high speed ratio when the vehicle is stationary with the brakes applied. The operating mode defaults to a normal ratio shift mode as the operator releases the wheel brakes. In an alternative embodiment of the invention, the control includes multiple enable switches for achieving manual selection of the ratios when a manual upshift sequence is desired.