Partial prefill of clutch for coast downshift conditions in a vehicle

A vehicle comprising:

• a transmission having a plurality of oncoming clutches, each of the plurality of oncoming clutches being hydraulically-actuated;
• a controller operatively connected to the plurality of oncoming clutches;
• an algorithm stored on and executable by the controller to cause the controller to:
• determine if at least one predefined coast condition is met;
• identify the plurality of oncoming clutches configured to be engageable during a downshift event from an initial gear ratio to respective other gear ratios, the initial gear ratio being greater than each of the respective other gear ratios;
• and
• at least partially prefill a first one of the plurality of oncoming clutches by generating a first pressure command to at least partially pressurize the first one of the plurality of oncoming clutches to a first staging pressure (PS1) if the at least one predefined coast condition is met prior to the downshift event;
• and
• wherein the first staging pressure (PS1) is defined as a first return spring pressure (PR1) minus a first variable correction factor (CF1).

A method of controlling a transmission, the method comprising:

• determining whether at least one predefined coast condition is met;
• identifying a plurality of oncoming clutches in the transmission configured to be engageable during a downshift event from an initial gear ratio to respective other gear ratios, the initial gear ratio being greater than each of the respective other gear ratios;
• wherein each of the plurality of oncoming clutches are hydraulically-actuated and include a respective biasing member characterized by a respective return spring pressure (PR) such that the plurality of oncoming clutches are fully engaged when the respective return spring pressure (PR) is applied;
• determining a respective staging pressure (PS) for the plurality of oncoming clutches, the staging pressure (PS) being the respective return spring pressure (PRS) minus a respective variable correction factor (CF);
• generating a pressure command to at least partially pressurize at least one of the plurality of oncoming clutches to the respective staging pressure (PS) if the at least one predefined coast condition is met prior to the downshift event.