Shift on the go transmission system

A method of shifting a transmission of a vehicle including a source of motive power, and at least one drive wheel;

• said transmission receiving input torque from said source of motive power, and to transmit output torque to said drive wheel;
• said transmission including a variable displacement hydraulic pump, fluid pressure actuated means for varying the displacement of said pump, and a hydraulic motor hydraulically coupled to said pump, said transmission further including a mechanical transmission having a first gear ratio and a second gear ratio, and fluid pressure actuated means for shifting said mechanical transmission from a neutral condition to one of said first gear ratio and said second gear ratio conditions;
• the method comprising the steps of:
• (a) when said mechanical transmission is in said first gear ratio, relieving said output torque transmitted by said hydraulic motor;
• (b) shifting said mechanical transmission from said first gear ratio to said neutral condition;
• (c) controlling fluid pressure at said fluid actuated means for varying the displacement of said pump, to synchronize the output speed of said hydraulic motor with the instantaneous input speed required for said mechanical transmission to operate in said second gear ratio;
• and
• (d) controlling the fluid pressure at said fluid pressure actuated means for shifting said mechanical transmission whereby said transmission is shifted into said second gear ratio.