I don't know either. My dad told me when you get the RPM just right and matched up to the trans it just goes right in to gear with out pushing in the clutch. I need to get my CDL but I realy don't like them long runs. They are so boring.
LOL once again same thing my dad says...he just knows what rpm will work to shift gears without even using the clutch..he was putting it into perspective for me by saying that new truck trannies are still manual with no synchros, but instead of the driver shifting, there is an electric motor that sense correct rpm to shift the gears on its own...so not a full manual, but in a sense gives an idea of how the shifting can be done clutchless at the right rpm...many guys with faceplated/proshifted trannies state that when shifting at high rpms you barely even touch the clutch for it to go into gear- it almost wants to fall in...some dont use the clutch at all