so is there any way i can change the behavoiur of my tranny not to shift to 4th until reaching 60Km/h(37mph), because right now it upshifts to 4th at 40Km/h when i let off the throttle to apply brakes.

bowden cable sets the shift points while you are opening the throttle, what thing should manages to prevent upshift when you let off the gas pedal??? this is all i want for a long time.

Is this behaviour (upshift when letting off throttle) because of Vacuum Leak or Bad Modulator, becuase i adjusted my modulator and nothing happened, i still have hard shifts.