The common terms are "rev" or "match" shifting. Almost all semi-truck drivers "float" the gears. This is fine with a transmission with no synchros... not so good otherwise.
My Borg-Warner Super T-10 tranny has every other synchro tooth ground off flat, (essentially removed) creating what is called a "crashbox". I need only take the pressure off the driveline by lightly lifting off the throttle before slamming into the next gear as smooth as silk. The crashbox is actually easier to shift without the clutch since there's only half as many synchros to do the job.
Your friend was undoubtably pressing the shifter gently against the sychros while waiting to the revs to match the speed of the next gear. It works and impresses the girls... but it's not a smart practice. You'll get away with it for a while but the synchos are brbutt and wear very quickly when abused.
Double-clutching is used during upshifting to simply give the driver something to do while waiting for the revs to fall, it isn't really necessary. Downshifting, you push in the clutch and take the tranny to neutral, release the clutch and rev the engine to the proper rpm and *hold* that engine speed. Next, you depress the clutch again, select the proper gear and release the clutch. There aren't 2 drivers in ten thousand that downshift properly by *holding* the rpm during a downshift. The common practice, since it's easier, is to rev to just above the proper rpm and catch the gear as the r's fall past the shift point. Almost the proper shift technique, only different.
You don't want to double-clutch a synchronized transmission either. It's a waste of time unless you catch the gear *perfectly*. If not, the synchros are doing their work anyway. Plus, you're placing undue wear on the throw-out bearing.
Here's a couple free tips:
Don't downshift at all unless your vehicle is heavy and you need the engine braking going down a hill. Brakes are cheaper and easier to replace than clutches.
ALWAYS buy an automatic. Especially if you pull or haul loads. -----
No Clutch Shifting 3107Do you even understand what a synchronizer is? Synchronizers are spring-loaded cone clutches that engage *before* the dogs come into contact...
- gpsman
