Answer:
If it's difficult to switch gears, if there's unnatural noises when switching gears, if the engine runs too high or too low when accelerating/decelerating ... list goes on
----------------------------------------------------------------------------------------------------Also when shifting if ur 3 gear pop is harder than usual you might have a problem. Transmissions are an easy fix if you do it yourself and its prolly not your transmission its either ur clutch gear teeth or your flywheel. Good luck