Present day vehicles use helical gears and synchromesh devices while in the gearboxes, that synchronize the rotation of gears which might be about to mesh. This gets rid of clashing from the gears and will make gear shifting less difficult. In July 2014, Randy Pitchford formally contested the Aliens: https://josuewkveq.liberty-blog.com/33916783/the-basic-principles-of-gearbox