Go BottomWhat is double-clutching
 | Mrwurm
Join Date: Feb 2002 Posts: 184 South East Michigan 
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2002-03-20 36515
I could'nt figure which forum to post this under, so it ended up here. I have heard the term 'double-clutching' used on occasion. What does it mean? How does it work?
Jerry
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| Paul Fox
Join Date: Posts: 1
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2002-03-20 36517
Ah, yesssss. Double-clutching is a hold over from pre-synchronized transmission days. Usually used when downshifting, but on REALLY rough gearboxes, can be used for upshifting as well. When shifting from say, 3rd to 2nd gear, you depress the clutch, move the shifter from 3rd to neutral, release the clutch, blip the throttle to match up gear speeds, depress the clutch again, move the shifter into 2nd. With some practice, and experience on the particular vehicle, it can be done smooth as silk. Sounds neat too ":^)
I do it on my tractor occasionally, just fooling around mostly. Also comes in handy on the town's firetrucks, as there are some pretty nasty hills, and you lose too much momentum waiting for the synchronizers to do their job. ....
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| Roy Jackson
Join Date: Posts: 1
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2002-03-20 36520
God! This goes back many years!!!
Prior to synchronized gears, there were non-synchroed gearboxes (manual tranny's, of course).
To shift without crunching gears, one had to "doubleclutch" during shifts to a higher (or lower) gear.
The process was:
1)Clutch
2)Shift into Neutral momentarilly
3)Clutch
4)Shift to the next (higher or lower) gear
It sounds cumbersome, but with practice, one could do it quite quickly and smoothly. Or, so I am told...this is before my time!
Tell ya the truth, I only doubleclutched in one vehicle, an early '50' International 1 ton truck. Doubleclutching was apparently common (especially on Hotrods and sportscars) up to the advent of synchroed tranmissions, although I believe it is still used on big trucks (18 Wheelers).
My tractor is a gear tranny (1990 JD 670). I do not have to doubleclutch when shifting...maybe when going into Reverse..if I do it, I don't even think about it. ....
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| David Waite1
Join Date: Posts: 1
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2002-03-20 36521
When I was a member of the fire company. we had a ford F700 and some old Macks all of them you had to double clutch on the way up and down. Gas engines you rev them up to about 3000 shift into nuetral then rev it back up to 2600 then into the next gear normally you never started in 1st it was to low you would just realse the clutch and have to push it back in. I did not drive to Mack diesel but it had to be double clutched to just not to the RPMs of the gas engines. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-03-20 36525
Yep, generally engine rpm is increased while in neutral for gearing down and idle rpm for gearing up. You also don't even need the clutch on some TX's. Just bump it into neutral for awhile and add rpm's if gearing down. Get it right and it just slides into the next gear. I've even read debates among transport drivers about whether it's easier on some TX's to not use the clutch.
Myself, I used to double clutch the LaSalle TX in my old shot-rod all the time. I probably didn't actually need to except for shifting speed, but it was 'neat.' My '52 Nash-Healey probably was synchro but I double clutched it anyway because it sounded 'neat.' Of course, the sense of neat things does change as we age, and fortunately so I guess.
....
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