did a search on "double clutching"---no info.

[PCarbonaro]

Guys, what is this technique? I have a clue. As I do some road racing, I am used to heel-toe shifting and rev matching, but the above term eludes me.

 

[Gary - K7GLD]

HMMMmm - *I* just did a search on "double clutch", and got *247* related threads...



Be sure you carefully read and mark ALL the vailable search options and parameters...

 

[nickleinonen]

needed on trans with no syncros [or dead syncros].

drive along, clutch and put in neutral, de-clutch and wait for rpm to be close to matched, clutch again and pull into gear. it is easier to do on larger diesel engines i think cause they rev down slowly-more flywheel/clutch mass.

[the ddc 60 series that is in my schools engine lab will take many seconds (5-6) to come down from 2200rpm to ±800rpm]

 

[Dkuhlman]

Double clutching is similar to rev matching only you let the clutch out again in neutral. So you depress the clutch, shift to neutral and match your revs to road speed, then depress the clutch again and complete the shift. Hence the term double clutch. Drop revs on the way up, raise them on the way down. It's also not really necessary in a modern synchromesh transmission.

 

[Joe G.]

If you ever ride with someone driving an old big rig (early 50s) you will see it in action. A skilled driver can shift very fast and smooth that way.

 

[jrlawler]

When I had my 01 HO 6 Spd I used to grab lower gears at high rpms to engine brake heavy loads. Double clutching (which is exactly what it says) makes it slide in there real easy like if you get your revs high enough. You can do it with the synchronizers but that is slower and will speed wear and tear. RPM matching with no clutch at all is what you could do on the older big trucks. I've got a buddy in CO that used to drive my Dodge like that. That's the sort of feel you get from driving big trucks through Mtn. passes for few years. I don't recommend any of us trying that!

 

[PCarbonaro]

Ok, I'm seeing that double clutching is really just a slow-mo heel-toe manuever, which probably couldn't be done in a big truck that doesn't have a brake pedal close enough to the accelerator pedal.

 

[Joe G.]

The brake pedal is not involved. Step on the clutch pedal. Shift to neutral. Let the clutch pedal up. Use the throttle pedal to sync the engine to the next gear speed. Step on the clutch pedal. Shift to next gear. Let up the clutch pedal.

 

[DBrickel]

Double clutching is not needed on these trucks. They have syncronized trannys. the older rigs built prior to early 50s didn't have this feature. It involves clutching, shifting into neutual, clutching again, and shifting into the next gear. the trick in the non syncroed trannys were matching the rpms to transmission gear speed. If not matched it could get ugly

 

[nickleinonen]

older rigs built prior to early 50s didn't have this feature.

and pretty much all transport truck / HD trannies currently too... [range box is usually syncro'd]



iirc, volvo has a full syncro 10 speed now... [5x 2range]

 

[SHobbs]

Clutch shifting what is that? I float mine, use the clutch for launch only. I know all the talk about the synchro's but I have never had a problem. Put 240k on a 3/4 Furd with no problems, the only problem is that the original throw out bearing fell apart.

 

[bmoeller]

With some of the more current Mack trannys, they still want you to double clutch. The T2050 (5spd ) is one of them. I think the T2060 was another. You can shift without doing it though. We have a T2050 in the '90 CH.

 

[RKohn]

I double clutch too...

Once when I leave the line and once more when I stop.

 

[BigEasy]

I'm with Kohn and Hobbs on this one... it's a bunch easier to NOT clutch than it is to double-clutch.



Every time you step on a pedal it costs you money... any of the three. Drive with that in mind, and your clutch, brakes, and fuel will last a LONG, LONG time.