Those manual shift 2 speeds usually have two stiff springs around the cable so the shift can be pre-selected. Then momentarily backing off the throttle and/or tapping the clutch pedal to unload the driveline torque lets the rear end shift be made very quickly. It takes a little practice to get the timing down pat.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!