Double clutch shifts into first gear

[DaveMcKenz]

Hi Guys,
I discovered that I can always easily shift into first gear while rolling, if I double clutch. It only takes a second or so, and it's generally when approaching a stop sign anyway. It seems to eliminate any fiddling or forcing into first gear.
Just thought I'd share. (915 transmission)
Dave

[Jack Stands]

It will certainly help as that synchro does take a beating more than the others.

[puddy]

I always do this too. Works better than a normal shift for me.

[needspeed]

+1. Double clutching eliminated my problem of having to force into 1st. (G50)

[onewhippedpuppy]

I always double clutch downshifts with my 915, it certainly seems to help smooth things out.

[Hnichols]

I double clutch on both my old cars as a matter of habit, not that I really have to. I actually enjoy the challenge. Single clutch shifts almost seem like cheating

[911pcars]

Double clutch on every downshift. It reduces the workload the synchros usually perform, and they will last longer.

[Eli W]

I do this too getting into reverse too at start up.

[Tremelune]

I double-clutch every downshift into 1st and 2nd in every car with a clutch pedal. Those two syncros are the primary reason most street transmissions are opened up, so protecting them directly contributes to how long you can go without having to open the transmission.

[JSV798]

Double clutch: that's nothing! I always toe and heel on down shifts to second

[911pcars]

Originally Posted by JSV798

Double clutch: that's nothing! I always toe and heel on down shifts to second

DC is a process that deals with mechanical harmony inside a gearbox. H&T is only a clutch engagement process. As for H&T, what do you do in the other 3 speeds?

S

[JSV798]

H&T is braking with DC! Imagine you are approaching a corner where you are going to change down a gear. First you have to brake. The you want to change down by doing a DC so have to lift off the brakes to blip the throttle, then back on the brakes. Not the swiftest method - you have to brake earlier that required.
So, as you approach said corner start braking with the ball of your foot; when you need to change down a gear, keep braking with the ball of your foot but rock your heel on the throttle to facilitate the DC. When done expertly your feet become a blur of action!

[911pcars]

Originally Posted by JSV798

H&T is braking with DC! Imagine you are approaching a corner where you are going to change down a gear. First you have to brake. The you want to change down by doing a DC so have to lift off the brakes to blip the throttle, then back on the brakes. Not the swiftest method - you have to brake earlier that required.

So, as you approach said corner start braking with the ball of your foot; when you need to change down a gear, keep braking with the ball of your foot but rock your heel on the throttle to facilitate the DC. When done expertly your feet become a blur of action!

Yes. Absolutely agree. Thanks for clarifying. However, many who H&T merely rev-match engine (flywheel) speed to the increased gearbox input shaft (clutch disk) speed so engagement is smooth(er). Those gas/clutch pedal motions don't mitigate gradual synchromesh wear INSIDE the gearbox.

MHO, DC isn't performed by the majority of those who do or don't H&T. I haven't observed a wide cross-section of drivers, but I know of only 3 other friends who DC (maybe I hang with the wrong crowd?). What's your experience with your friends' shifting habits?

Sherwood

[JSV798]

I think DC and H&T are something car enthusiasts do; most of my friends just drive and use the synchromesh. I DC (without throttle blip) on the change from 1st to 2nd first thing when the gearbox is cold as it's the only way to get a clean change, even tho' the gearbox has been rebuilt in my ownership. Once warm the same change is OK without DC, but I always H&T from 3rd to 2nd; just seems too brutal otherwise. changing down from 5th to 4th or 4th to third I'll most likely just DC with a throttle blip.

[JAR0023]

Add my name to the double de-clutcher club. Very satisfying when the shifter falls into place with little pressure.

[Canada Kev]

Sometomes I double clutch on downshifts, sometimes I don't. And it's usually just for second. Shifting into first, I'm almost always going very slowly or stopped. If moving at any speed, I'd DC for sure to hit first.

I remember driving some transport trucks and you HAD to double clutch if it was used, otherwise it was shifting with no clutch. Those gear boxes don't have synchros. Heel and toe wasn't really an option, either. But that's where clutchless shifting helped. Left foot braking and right foot to raise the revs on downshifts. It just becomes second nature to rev match all the time or the thing won't go into gear and you make lots of expensive sounding noises.

They aren't exactly sports cars, but with no trailer, 2000 lbs-ft of torque and skipping every second or third gear (on an 18 speed), it sure feels like it.

[proporsche]

As Kev said......I just wonder why do you have to shift (or what makes you to shift) into 1st gear while traveling?Maybe to slow the car before stop sign? But you are going to stop any way right-unless in California...
My mentor has always told me never shift in 1st gear if the car is moving.That is the reason you will find a lot of 911 owners having problem with the synchro ring in 1st.

Ivan

[bigel]

This is an interesting topic. I myself haven't done/noticed the whole double clutch thing, though I don't usually downshift into 1st gear all that often.

I'm wondering what the mechanical reason is for the assistance provided by double clutching...can anyone shed some light on what's actually going on in the gearbox?

[Tremelune]

A very frequent trait of people who drive stick, at least in my experience, is a propensity to lug the engine in a higher gear to avoid a downshift, which is not good for your engine and tends to promote slipping the clutch as compensation for getting moving in too high a gear. People just don't like being in 1st. I generally try not to let revs drop much below 2,000rpm, so if I want to make a low-speed turn onto a side street without getting rear-ended or lugging the engine, I often need to be in 1st gear.

The purpose of double-clutching (which is distinct from rev-matching) is to match the rotation of the synchros and gears in your transmission before they are engaged (or synchronizer ring? I'm at the limit of my understanding). Its only value is preserving synchros or shifting when there are no synchros. I treat the 915 as if it has no synchros, because it barely does (at least in first and second).

The purpose of heel-toe is to reduce the amount of time it takes to shift while braking so you can get back on the gas as soon as possible. There is virtually no reason to do this on the street, unless it's for fun/practice.

With regard to downshifting for a stop: avoid doing this. Use the brakes that were designed for this purpose instead of putting unnecessary wear on the drivetrain. There is safety value in being in a proper gear for the vehicle speed while slowing down, and there are cases when slowing the car without the brakes might be desirable (on a long, steep grade where there is a real danger of your brakes fading from heat—literally in mountains), but downshifting for the express purpose of slowing the car moves the wear from (comparatively) cheap brake pads/rotors onto the engine, clutch, and transmission. To be clear, there's nothing wrong with using the engine to slow down, but I often see people downshift to slow the car faster instead of using their brakes, and there's no practical reason for it.

I think I'm off on an evangelical tangent at this point...

[NYNick]

What's the reason everyone is so anxious to get into first gear when they're coming to a stop anyway? Stop, shift, go.

The guy I bought my first Porsche from in 1971 told me to downshift only when I had to, like when spirited driving. As he explained, brake pads are much cheaper than synchros and clutches.