Can someone please explain the "double clutching" technique to me?

 

Many years ago on a farm far, far away, I learned to drive an old dump truck. It had a non-synchronized transmission that required "double-clutching" in order to shift. The driver depressed the clutch pedal to pull the transmission out of gear, release the clutch momentarily, and then depressed the pedal a second time in order to give the next gear a chance to mesh cleanly.

As a precursor to life as a drag racer I was immediately intrigued by the possibility of being able to move the lever quickly and smoothly enough to complete the shift with only one clutch action. I could do it about 60% of the time. The other 40% of the time there was enough commotion resulting from grinding gears to attract my Dad's attention. I was demoted from driver to grain shoveler fairly quickly. Such was the life of a 12 year-old in those days.

That was "double-clutching" in an ancient context. If it means something else today, I apologize for taking up time and space.

c

 

they did mention it in fast and furious but I couldnt figure how it had anything to do with quarter mile.It just reminded me of dumptrucks and big rigs.It would be slower than granny shifting if you did it in a race I would think

 

Thank you both. That was my thought exactly. I noticed them saying it in the Fast and the Furious the other night and thought maybe there was something I was missing. Could they have meant power shifting and were just too stupid to put it together correctly. Ya know, just like how N.O.S.(Nitrous Oxide Systems) became known as Nawz in the ricer world?!?

 

Double clutching is typically used in big, heavy transmissions, and is required where there are no synchros- You clutch to go to neutral, let the clutch out and match the engine RPM's to the next gear, up or down, then clutch again and shift into gear- can be used to save wear and tear on trannys, or nurse one that is failing- I don't know why anybody would do it racing, although there are plenty of race cars that use 'crash boxes', non-synchro transmissions- just advanced driver technique or showing off, I guess-

If you get real good at matching RPM's, you can shift without a clutch, but you want to be coasting, with no loads on the gears- just ease it out of one gear, adjust engine RPM and slide it into the next- drive a company's trucks like that for years-

 

Even a modern highway truck with a Roadranger transmission should still be double clutched. Many truckers feel they can still do a smooth shift without the clutch but it's hard on the syncros. The syncros have a slight back cut to help keep them engaged. By slightly depressing the clutch, it takes the load off the syncros and allows you to pull it out of gear without forcing the syncro out of the back cut. Lightly depressing the clutch again before shifting into the next gear just allows a smoother, less damaging, shift.

It's more common to double clutch going down in gears than up. As you drop down a gear, the engine rpms need to be higher for the next lower gear.

Today's automotive transmissions should never need to be double clutched.

I wish everyone would stop using F&F as a reference. The movie is Hollywood fiction. It's not even close to real life. You can't pull a wheelie and do a burnout at the same time. You can't reprogram a fuel map during a 9 second pass etc.

 

Sigh, I can't tell you how many times I hear about people double clutching during a drag race, I just shrug it off and walk away. It happens all the time.

 

let me guess, you just watched fast and the furious.

haha jk man, you dont have to worry about it its really only used on trannys that don't have syncros.

no help at all in drag racing. what you need to learn about is powershifting (shifting while keeping gas to the floor)

 

steve mcqueen did it

 

this really serves no purpose on most of todays cars, like when i blew my clutch i just revved high and let the rpms drop then popped it in gear to shift down and just shifted up slowly lol.

 

I've got my PCM programmed to double-clutch my 4L60E!

WD

 

I watched the vid , its been a long time since Iv seen it.
I wonder if the reason he was shifting like that was for the cameras or the clutch pedal was on the floor?
I dont know mustangs but wasn't that a 390 car?

 

prolly like 289 with obviously open rear end. haha

 

Besides lacking syncros in the transmission; that old Mustang in Bullitt does a nice peg-leg burn out. The Mustang has always been a piece of crap I guess.

 

I have to double clutch my t56 on the street.
HEHEHEHEEHEHEHHH