Method of calibrating clutches in transmissions

A method of calibrating clutches in a transmission operably connected to an engine and having said clutches for selectively interconnecting an input drive shaft, an output drive shaft, and a plurality of gears rotatably housed in said transmission in driving relationship with said input and output drive shafts such that a selective engagement of said clutches will effect a varying of the speed of operation of said output shaft for a given speed of operation of said input shaft, said transmission further having an electrical control system including a microprocessor responsive to switches actuated by manual movement of a gearshift lever between a plurality of positions for controlling said clutches in the transmission, said clutches being operably connected to a hydraulic system for effecting the actuation of each respective said clutch by an increase in hydraulic pressure for each said clutch as controlled through operation of said microprocessor, the method comprising:

• restraining said output shaft from rotational movement;
• running said engine in a no-load condition and determining a reference engine speed corresponding to said no-load condition;
• incrementally increasing the hydraulic pressure for a selected clutch while all other appropriate clutches are engaged to permit a transfer of rotation power from said engine driven input shaft to said output shaft through said selected clutch when said selected clutch becomes engaged;
• and
• recording a value corresponding to the hydraulic pressure required to effect engagement of said selected clutch, determined by a loading of said engine as measured by a decrease of said current engine speed below said reference engine speed.