Modern-day automobiles use helical gears and synchromesh devices during the gearboxes, that synchronize the rotation of gears that happen to be about to mesh. This eliminates clashing from the gears and would make equipment shifting simpler. Spur and helical gears are used in the sliding mesh gearbox to act. https://gearbox07529.madmouseblog.com/14279616/the-basic-principles-of-gearbox