Automatic downshift and override control for a transmission

A hydrostatic transmission system for a work machine, comprising:

• a source of hydraulic fluid;
• a pump for pressurizing the hydraulic fluid;
• a motor group connected with the pump for receiving the pressurized hydraulic fluid, the motor group having high and low speeds for driving an output in either forward or reverse directions;
• and
• a control mechanism for determining when the motor group is driving the output in a reverse direction and at the high speed and for automatically changing the speed of the motor group to the low speed in response to the determination.

A hydrostatic transmission system for a work machine, comprising:

• a source of hydraulic fluid;
• a pump for pressurizing the hydraulic fluid;
• a motor group connected with the pump for receiving the pressurized hydraulic fluid, the motor group having a defined speed range for driving an output in either forward or reverse directions;
• a control device connected with the motor group , the control device selectable to send a speed signal to the motor group for driving the output at a predetermined speed within the speed range;
• a sensing device;
• and
• a controller connected with the control and sensing devices for sending a control signal in response to a predetermined speed signal from the control device and predetermined input from the sensing device to automatically override the selected speed signal from the control device.