Double Clutching in 4L

[Mguy]

As winter sets in and snow drifts make uphill dirt switchbacks even more fun, I'm in 4L more often than usual. Just last week, for no particular reason, in 4L I double clutched from 4th to 3rd. Amazingly, it made the shift butter smooth and noticeably better than an ordinary shift. A little more playing around and it became clear that no throttle in neutral was needed.

So this downshifting experience was unexpected. Double clutching in 2H and 4H had never been necessary, and over the last 90K miles I had thought the same with 4L. Anyway, a new habit for 4L mountain climbing seems in order.

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[J-P 2025]

No throttle in neutral? Isn't that the point of double clutching? Did I miss understand something?

 

[Flip]

The process of double clutching includes the following steps:

1. Release the Accelerator: The driver releases the throttle.
First Clutch Disengagement:
2. The clutch pedal is pressed down, and the gearbox is shifted into neutral.
Engine Speed Matching:
3. The driver releases the clutch pedal and revs the engine to match the speed of the next gear.
4. Second Clutch Disengagement: The clutch pedal is pressed again, and the driver shifts into the desired gear before releasing the clutch.

Interesting.

 

[J-P 2025]

The process of double clutching includes the following steps:

1. Release the Accelerator: The driver releases the throttle.
First Clutch Disengagement:
2. The clutch pedal is pressed down, and the gearbox is shifted into neutral.
Engine Speed Matching:
3. The driver releases the clutch pedal and revs the engine to match the speed of the next gear.
4. Second Clutch Disengagement: The clutch pedal is pressed again, and the driver shifts into the desired gear before releasing the clutch.

Interesting.

Yup. That's the way I was taught and trained

 

[Mguy]

No throttle in neutral? Isn't that the point of double clutching? Did I miss understand something?

I get enough RPM "hang" from 4 to 3 that no additional throttle seems to make a difference.
I think your point though is generally correct, as also stated by @Flip. When a vehicle needs help with a downshift, raising the RPMs is part of the trick. 4L, at least for my Wrangler, seems to change the situation. Maybe different for other low gear vehicles, I don't know.

 

[au176]

As winter sets in and snow drifts make uphill dirt switchbacks even more fun, I'm in 4L more often than usual. Just last week, for no particular reason, in 4L I double clutched from 4th to 3rd. Amazingly, it made the shift butter smooth and noticeably better than an ordinary shift. A little more playing around and it became clear that no throttle in neutral was needed.

So this downshifting experience was unexpected. Double clutching in 2H and 4H had never been necessary, and over the last 90K miles I had thought the same with 4L. Anyway, a new habit for 4L mountain climbing seems in order.

Double-clutching simply gives the engine RPM's time to match the transmission. Driving uphill, especially in the snow, allows this to happen naturally. No revving necessary.

When I drove semi's, one tended to double-clutch when learning to drive (or learning to drive a different truck), because the RPM's needed to match your road speed and gear choice VERY closely. It had a way of helping you slow down the process, and learn the timing. Once you got a feel for what gear you needed to be going to at what speed, it became easy to "slip-shift" gears using no clutch at all.

In modern automotive manual transmissions, gear synchronizers make it easier to shift, which generally makes double-clutching unnecessary. I don't know if heavy truck transmissions have gotten to this point, as I haven't driven a manual semi in about 12 years.

 

[au176]

The process of double clutching includes the following steps:

1. Release the Accelerator: The driver releases the throttle.
First Clutch Disengagement:
2. The clutch pedal is pressed down, and the gearbox is shifted into neutral.
Engine Speed Matching:
3. The driver releases the clutch pedal and revs the engine to match the speed of the next gear.
4. Second Clutch Disengagement: The clutch pedal is pressed again, and the driver shifts into the desired gear before releasing the clutch.

Interesting.

In number 3 above, while that is true, if the vehicle slows enough to match the engine RPM's, no revving is necessary.

 

[J-P 2025]

In number 3 above, while that is true, if the vehicle slows enough to match the engine RPM's, no revving is necessary.

I'll play around with my JL today in the snow uphill and see how it responds. I only have a 1000 miles on it so far. Love these discussions.
On my Willys, try getting into 1st without double clutching.

 

[Mguy]

In number 3 above, while that is true, if the vehicle slows enough to match the engine RPM's, no revving is necessary.

Now that makes the most sense. When downshifting I'm rapidly losing speed--and much needed momentum for maintaining traction in the snow!

 

[Mguy]

I'll play around with my JL today in the snow uphill and see how it responds. I only have a 1000 miles on it so far. Love these discussions.
On my Willys, try getting into 1st without double clutching.

In 4L, I don't use gears 1 and 2 for "driving." They're really just for crawling over obstructions. I don't think I ever had to do a 2 to 1 downshift while moving.

Edit,
At 1K miles, your transmission is still breaking-in. There's likely some stiffness that is yet to fade away.

 

[J-P 2025]

In 4L, I don't use gears 1 and 2 for "driving." They're really just for crawling over obstructions. I don't think I ever had to do a 2 to 1 downshift while moving.

Edit,
At 1K miles, your transmission is still breaking-in. There's likely some stiffness that is yet to fade away.

You are probably right.
I am so happy I went with the manual. It behaves more like a car manual than my truck manual transmissions but its a lot of fun. Takes getting used to.

 

[Mguy]

It behaves more like a car manual than my truck manual transmissions . . . .

Exactly, and that, I think, is why there so many clutch complaints on this board. The JL car-like clutch is not always expected by those who are mostly truck experienced. As for being car-like, I think the Jeep is top end, foreign sports car equivalent. Anyone renting a sedan in the third world should understand.

 

[Flip]

I've heard of this double clutch before, mostly in movies. I've never actually tried it myself but it is very interesting.

 

[yokramer]

Double clutching has been made pretty much moot with synchros. You can get the same effect just waiting for the revs to drop to match the gear rpm with the engine rpm, which is essentially what you are doing by taking the time to put the trans in neutral and then into the next hear.

 

[J-P 2025]

Double clutching has been made pretty much moot with synchros. You can get the same effect just waiting for the revs to drop to match the gear rpm with the engine rpm, which is essentially what you are doing by taking the time to put the trans in neutral and then into the next hear.

It's that waiting time you trying to avoid

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