Modern cars use helical gears and synchromesh gadgets from the gearboxes, that synchronize the rotation of gears that are about to mesh. This eradicates clashing in the gears and would make gear shifting a lot easier. Spur and helical gears are used in the sliding mesh gearbox to act. https://gearbox98530.bcbloggers.com/32981240/not-known-factual-statements-about-gearbox