When a vehicle or machine including a transmission is operated in a band around a shift point of the transmission, the transmission may experience shift hunting which can result in increased fuel consumption, operator discomfort or irritation, and transmission wear or damage. Delaying a shift point may alleviate the shift hunting condition, but may cause asynchronous shifts. When a drivetrain includes flexible or fluid couplings, such as a torque converter, these couplings may absorb the shocks from asynchronous shifts. However, in a drivetrain without a flexible or fluid coupling, forces and shocks to the driveline resulting from asynchronous shifts may cause damage. Jerking from the asynchronous shifts may cause operator discomfort or irritation.
U.S. Pat. No. 6,663,534 discloses a method for preventing oscillating gearshifts of a motor vehicle automatic transmission with an electronic transmission control device. The control device monitors the current road resistance from a comparison of measured vehicle acceleration with a theoretical vehicle acceleration and determines therefrom the value of differential acceleration. The engine torque is reduced if: (a) the position of the accelerator pedal of the motor vehicle is greater than a first limit value; (b) the differential acceleration is greater than a second limit value; (c) the measured vehicle acceleration is greater than a positive third limit value; (d) the theoretical impingement in the next higher gear is lower than a fourth limit value; and (e) the current engine speed is greater than a fifth limit value.