shifting and double clutch instruction

[Bill Douglas]

What a PITA.

I occasionally do a double clutch from 2nd into 1st. But the rest of the time NO WAY.

There must be something badly wrong with this guys gearbox if he deeds to do this every shift. Sure wear and tear, but I'd rather do a rebuild every 20 years instead.

And I know how to double clutch; I used to be a truck driver back in the old - no syncro days.

[BLACK3.2]

Originally Posted by Bill Douglas

What a PITA.

I occasionally do a double clutch from 2nd into 1st. But the rest of the time NO WAY.

There must be something badly wrong with this guys gearbox if he deeds to do this every shift. Sure wear and tear, but I'd rather do a rebuild every 20 years instead.

And I know how to double clutch; I used to be a truck driver back in the old - no syncro days.

So much this. Parts wear out. They're supposed to. Use proper technique, but double clutching on every shift??? Syncros enable you to shift faster. If you want to shift slow buy a 356.

You know what else prolongs the life of your car? Keeping it parked.

[kyngfish]

I don’t really have issues shifting. But I figured I’d give this a try. Honestly it didn’t feel any better with respect to matching speeds. If anything it felt like I was forcing it more. Any thoughts on why?
I tried a few different methods, and I’m not a novice shifter, I felt like I was double clutching evenly and getting it into gear but it never felt like it was going in as easy as when I do it my normal way.

Usually when I downshift I blip the throttle up past 3k right before putting it into the lower gear and this works fine.

[gsxrken]

Originally Posted by kyngfish

I don’t really have issues shifting. But I figured I’d give this a try. Honestly it didn’t feel any better with respect to matching speeds. If anything it felt like I was forcing it more. Any thoughts on why?
I tried a few different methods, and I’m not a novice shifter, I felt like I was double clutching evenly and getting it into gear but it never felt like it was going in as easy as when I do it my normal way.
Usually when I downshift I blip the throttle up past 3k right before putting it into the lower gear and this works fine.

Blipping the throttle does nothing helpful if the clutch is in when you do it. Revving the engine when in neutral in the middle of a true double-clutch during a downshift does increase the matching revs of the trans gears as each lower gear is selected.




At first I thought this video was at bit unnecessary, but there has been so much good feedback on it that I guess it was helpful. Folks really didn’t know what double-clutching meant? Turns out some didn’t. It really does mean pressing the clutch in twice. It’s not mandatory, but there’s a place and a time for it.

[Gordo2]

Not nearly as in depth as Knightrace - but another video, with me doing my best to describe what occurs as you double clutch:



BTW - I'm with Bill and others, drive it hard but well and rebuild every 20 yrs...

[kent olsen]

One other thing about shifting, my opinion. Nearly ever car I've owned since I was 16, now 77, has had a clutch. I've learned to heel and toe and double clutch. Matching the rpm before releasing the clutch. In all those years I've never used up a clutch. Now when I've pulled the engine for what ever reason I always replace the disc, pilot and throwout bearing and the old disc always looked ok.

[911pcars]

Originally Posted by Gordo2

BTW - I'm with Bill and others, drive it hard but well and rebuild every 20 yrs...

Gordo, Nice visual and explanation. However, the accepted rebuild every 20 years usual involves the last few (or many) years of gradual failure of the synchro and shifting deficiencies, often at the expense of the 2nd or 3rd car owner. This results in premature wear of 1st and 2nd gears over planned, long-life gearbox components (other gears, bearings, etc.). Many owners end up altering proper shifting techniques like using 2nd gear instead of 1st gear for low speed acceleration (potential engine lugging), upsetting high speed car balance while downshifting as well as extended clutch disc wear, all as a result of not double-clutching.

During a drivetrain drop after 27,000 miles, I measured the clutch disk lining thickness. The spec for a new clutch is 8.1 +/- 0.3mm. The measurement below with my low-buck digital vernier was close enough to spec to indicate double-clutching results in minimal clutch slippage (and wear) as it happens during typical take off and up/down shifting.



As for double-clutching, here's an easy low-speed practice routine. On an empty road:

1. Bring road speed up to a steady 20 mph in 4th gear.
2. Shift to neutral, then engage the clutch (pedal up).
3. Rev the engine a few hundred rpm above the normal rpm it would be in 3rd gear (e.g. 1500 rpm at 20 mph in 4th > 1800 + 200 rpm in 3rd)
4. Depress clutch during step 3 and complete the shift from 4th > 3rd

The engine speed and shift transition between step 3 and 4 should be seamless. Experiment with various pre-shifting engine revs. Practice until you get it as close as you can. Practice the same 4th > 3rd gear downshift at different vehicle speeds. Remember that 1st and 2nd gears provide the most torque multiplication and require more engine revs when downshifting into those gears.

Here's a 901 gearbox chart that graphically shows vehicle speeds at each gear position. Compare the relative engine speeds between 3rd and 4th gear at 20 mph, then between 1st and 2nd. Adjust the revs accordingly.



Sherwood

[Otter74]

Great video - thanks.

Originally Posted by Gordo2

Not nearly as in depth as Knightrace - but another video, with me doing my best to describe what occurs as you double clutch:



BTW - I'm with Bill and others, drive it hard but well and rebuild every 20 yrs...