Driveline engagement/disengagement

A transmission system for controlling the transmission of torque from an input shaft to an output shaft said transmission system including:

• at least one shiftable coupler mechanically linked to a range shift lever;
• a plurality of electro-hydraulic powershift clutches which, together with said coupler, select a gear speed ratio between said input and output shafts, at least one of said powershift clutches being located between the coupler and the input shaft whereby said coupler is selectively driven through said one powershift clutch;
• a dump valve through which hydraulic fluid is applied to or released from said powershift clutches;
• a clutch pedal, said clutch pedal when in a fully depressed position permitting synchronized shifting of said coupler;
• means for sensing that said clutch pedal has been depressed at least as far as a threshold point, said threshold point being between a released position and said fully depressed position;
• and,
• means responsive to said sensing means for controlling said dump valve to release fluid from said powershift clutches as said clutch pedal is depressed past said threshold point.

In a vehicle transmission system having at least a first coupler responsive to movement of a range shift lever mechanically linked thereto between first and second positions for selecting a first or a second range of gears said second range of gears being higher than said first range, a microprocessor responsive to actuation of powershift switches for energizing a plurality of electro-hydraulic powershift clutches to thereby select one powershift gear within the selected range, and a clutch pedal movable between a depressed position and a released position for controlling the flow of hydraulic fluid to said powershift clutches, the method comprising:

• sensing the position of said range select lever;
• detecting a shift of said range select lever from one of said positions to the other;
• and,
• generating signals to energize said powershift clutches to select the lowest powershift gear when said range shift lever is shifted from said first to said second position and the highest powershift gear when said range shift lever is shifted from said second to said first position, said lowest and highest powershift gears being separated by a least one other powershift gear.