A method of controlling a transmission in a motor vehicle, comprising: providing N automatically selectable gear ratios of the transmission, the N automatically selectable gear ratios including a minimum gear ratio (RMin) and a maximum gear ratio (RMax), a transmission control circuit for operably controlling the transmission, an internal combustion engine operably producing input torque to the transmission, an engine control circuit for operably controlling the engine, a data link establishing electrical communication between the engine control circuit and the transmission control circuit, and an engine brake operably coupled to the engine; receiving a first signal from a throttle position sensor corresponding to a position of an accelerator pedal, a second signal from the engine brake corresponding to an engine brake status, and a third signal corresponding to a cruise control status; determining an autobrake preselect state as a function of a comparison of the first signal to a threshold, the second signal, and the third signal; measuring grade with a sensing device and communicating the grade measurement to the transmission control circuit; receiving a fourth signal corresponding to a service brake input from the vehicle; determining a desired maximum acceleration limit of the vehicle based on the measured grade and fourth signal; calculating a predicted vehicle acceleration based on the grade and an estimated vehicle mass; measuring a current vehicle acceleration; calculating the difference between the predicted vehicle acceleration and measured vehicle acceleration; computing an estimated required tractive braking effort based on estimated vehicle mass, desired maximum acceleration limit, grade, and the calculated difference; determining a current gear ratio from the N automatically selectable gear ratios of the transmission; calculating an estimated tractive braking effort for each automatically selectable gear ratio from the current gear ratio to the maximum gear ratio until the estimated required tractive braking effort is approximately equal to or greater than the calculated estimated tractive braking effort; selecting the gear ratio between the current gear ratio and the maximum gear ratio that corresponds to the estimated required tractive braking effort being equal to or greater than the calculated estimated tractive braking effort; and controlling shifting from the current gear ratio to the selected gear ratio for the operation of the transmission if the selected gear ratio is different from the current gear ratio. providing N automatically selectable gear ratios of the transmission, the N automatically selectable gear ratios including a minimum gear ratio (RMin) and a maximum gear ratio (RMax), a transmission control circuit for operably controlling the transmission, an internal combustion engine operably producing input torque to the transmission, an engine control circuit for operably controlling the engine, a data link establishing electrical communication between the engine control circuit and the transmission control circuit, and an engine brake operably coupled to the engine; receiving a first signal from a throttle position sensor corresponding to a position of an accelerator pedal, a second signal from the engine brake corresponding to an engine brake status, and a third signal corresponding to a cruise control status; determining an autobrake preselect state as a function of a comparison of the first signal to a threshold, the second signal, and the third signal; measuring grade with a sensing device and communicating the grade measurement to the transmission control circuit; receiving a fourth signal corresponding to a service brake input from the vehicle; determining a desired maximum acceleration limit of the vehicle based on the measured grade and fourth signal; calculating a predicted vehicle acceleration based on the grade and an estimated vehicle mass; measuring a current vehicle acceleration; calculating the difference between the predicted vehicle acceleration and measured vehicle acceleration; computing an estimated required tractive braking effort based on estimated vehicle mass, desired maximum acceleration limit, grade, and the calculated difference; determining a current gear ratio from the N automatically selectable gear ratios of the transmission; calculating an estimated tractive braking effort for each automatically selectable gear ratio from the current gear ratio to the maximum gear ratio until the estimated required tractive braking effort is approximately equal to or greater than the calculated estimated tractive braking effort; selecting the gear ratio between the current gear ratio and the maximum gear ratio that corresponds to the estimated required tractive braking effort being equal to or greater than the calculated estimated tractive braking effort; and controlling shifting from the current gear ratio to the selected gear ratio for the operation of the transmission if the selected gear ratio is different from the current gear ratio.