What is the proper technique for upshifting in a non-synchronized transmission?

DOUBLE-CLUTCHING is required for non-synchronized transmissions used in most heavy commercial vehicles. Unlike car transmissions (synchronized), truck transmissions require the driver to match the rotational speed of the transmission input shaft to the gear being selected — otherwise gears grind. THE DOUBLE-CLUTCH UPSHIFT SEQUENCE: (1) FIRST CLUTCH PRESS: Depress clutch, move shifter to neutral; (2) RELEASE CLUTCH: Release clutch while in neutral; (3) REV MATCH: Reduce throttle (or wait) until engine RPM drops to the correct range for the next higher gear; (4) SECOND CLUTCH PRESS: Depress clutch; (5) ENGAGE GEAR: Move shifter into the next higher gear; (6) RELEASE CLUTCH: Smoothly release clutch while applying throttle. TIMING IS CRITICAL — shifting too early (engine RPM too high for the target gear) causes a 'grind' and refuses the shift; shifting too late (RPM too low) is easier on gears but reduces momentum. LEARNING THE RPM RANGES: experienced drivers know their truck's RPM shift points intuitively — typically 1,200-1,500 RPM for upshift, falling to ~1,000 RPM before selecting next gear. DOWNSHIFTING uses the same double-clutch principle but with a rev increase (engine rev-matching upward rather than downward, because you're engaging a lower gear that requires higher RPM).