A power machine having a drive system for propelling the power machine over a support surface, the drive system including a hydraulic pressure source including at least one hydraulic pump capable of providing pressurized fluid as an output and a drive assembly including a hydraulic motor in fluid communication with the hydraulic pressure source and switchable between a first displacement arrangement and a second displacement arrangement, the first displacement arrangement having a larger displacement than the second displacement arrangement and further characterized by: the drive assembly further including: a drive control valve operably coupled to the hydraulic pressure source and configured to provide pressurized fluid from the hydraulic pressure source to the hydraulic motor to cause the hydraulic motor to rotate; a shift valve (200, 240) configured to receive pressurized fluid from the hydraulic pressure source and provide a shift signal to the hydraulic motor for selecting one of the first displacement arrangement and the second displacement arrangement; and a sensing device capable of generating a load signal indicative of a load condition provided by the drive assembly; and an electronic controller in communication with the sensing device and configured to provide an electronic control signal to the shift valve to control the displacement of the hydraulic motor in response at least in part to the load signal; and wherein the drive control valve is in communication with an input of the shift valve (200, 400) and is configured to provide a pressure to the shift valve. the drive assembly further including: a drive control valve operably coupled to the hydraulic pressure source and configured to provide pressurized fluid from the hydraulic pressure source to the hydraulic motor to cause the hydraulic motor to rotate; a shift valve (200, 240) configured to receive pressurized fluid from the hydraulic pressure source and provide a shift signal to the hydraulic motor for selecting one of the first displacement arrangement and the second displacement arrangement; and a sensing device capable of generating a load signal indicative of a load condition provided by the drive assembly; and a drive control valve operably coupled to the hydraulic pressure source and configured to provide pressurized fluid from the hydraulic pressure source to the hydraulic motor to cause the hydraulic motor to rotate; a shift valve (200, 240) configured to receive pressurized fluid from the hydraulic pressure source and provide a shift signal to the hydraulic motor for selecting one of the first displacement arrangement and the second displacement arrangement; and a sensing device capable of generating a load signal indicative of a load condition provided by the drive assembly; and an electronic controller in communication with the sensing device and configured to provide an electronic control signal to the shift valve to control the displacement of the hydraulic motor in response at least in part to the load signal; and wherein the drive control valve is in communication with an input of the shift valve (200, 400) and is configured to provide a pressure to the shift valve.