5hift

I do the same procedure also. I think it's http://www.happytogether.com/318ti/notebook/shifting/ that you were talking about. I posted it a awhile back.

Good reading. Thanks Marcucci.



Does this mean it's best to change MTF sooner than what Honda recommends? If so, how often? Thanks.

I don't have the 5ft gear grind, but I'll take this into precaution.

shik0me

Yes, that's the one. Thanks for posting that again, one more for the bookmarks.

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Two-Five Boy

I've been having this problem as well, although it only occurs when the car is cold.

Usually it happens when I'm shifting slowly, almost as if I'm clicking into neutral then to 2nd. However, I don't get this problem as often when I shift quicker w/o hesistation.

MY guess is the tranny is cold/not lubricated and the synchros are not mated properly, hence it has a problem matching the rpm's when I "granny shift".

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Akimoto

I was told that double-clutching would produce less wear to the syncros. So is this not true then? I double clutch by habit now tho haha.

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marcucci

5hift, you should change ALL fluids more often than Honda recommends. Their service intervals are based on conservation, not on reliability. Most people don't keep their cars past 150k miles and Honda certainly doesn't warranty them that far.

Akimoto, double-clutching will help keep the synchros from wearing as much but it is so marginal as to be foolish to worry about. The synchros are there for a reason, double-clutching just gives people something to do and talk about. If you want to do something productive, learn to heel-toe.

pter

I don't have problems rev-matching into 1st. Just getting into 1st from a complete stop.

A Honda mechanic I know recommends changing the tranny fluid with every 3rd oil change. So, basically every 9k-15k miles you change both.

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_SBradley_

Isn't the ability to heel-toe pretty much a prerequisite to double clutching? I mean, the actions required to perform a double-clutched, rev-matched downshift are a superset of those required to perform a single-clutched, rev-matched downshift.

The conditions where I find that double clutching really does help are when the car is cold, and especially when the ambient temperature is also pretty low. The first few gear changes from my driveway are always particularly tough, but double clutching helps greatly, even on top of single-clutched, rev-matched shifts.

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marcucci

Only if you want to execute it well. You don't have to heel-toe to rev match, only if you want to be effective.

axio

Can someone FAQ this. This is like a transmission/shifting Bible here... Thanks Marcucci!

_SBradley_

OK, true, you can perform a rev-matched downshift without heel-toeing -- but only if you're not braking at the time. (Unless you're thinking of a break in the braking while you blip the throttle -- yikes!)

Since the majority of downshifts occur during braking, what I meant was that, in order to include double clutching as a part of your everyday driving, heel-toeing is a prerequisite to double clutching.

If that's not what you meant, please explain further.

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beaty

Great write-up marcucci! But one thing I don't understand here... why would double-clutching cause more clutch wear? During double-clutching, when you downshift to neutral and rev the engine, the clutch is fully engaged at the moment you rev-match. It's not that you're revving the engine with clutch half engaged, which would promote wear.

On the contrary, I think more clutch wear would occur if you just rev-match without double-clutching. The reason is if you only do rev-match (with clutch disengaged), you are not speeding up the layshaft to match the speed of the engine. So when you clutch out (after downshifting) the wear would occur due to greater friction caused by the speed differentiation of the engine and layshaft. Does that make sense?

Another thing is how would rev-matching accomplish the same purpose as double-clutching? I thought that rev-matching only helps smoother transition when downshifting. It does not speed up the layshaft and driveshaft to match the engine speed as double-clutching would do. Am I correct?

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marcucci

Simon, no correction. You're right.

With double-clutching you are increasing clutch wear with 2x the engagements you'd have. Yes, there are lower forces at work but if you are properly rev-matching, you are properly rev-matching. There is little wear there. Double clutching is only less wear if you properly rev-match, and if you can do that, there's no need to double-clutch.

As I previously described the transmission is still viscously coupled to the motor with the clutch disengaged. You can still rev-match just fine and get things to engage smoothly without double-clutching. Trust me, I've been doing it for years.

beaty

Haven't someone FAQ'ed this thread yet??

Well Todd thanks for the explanation. It's great! I've seen in videos that some racecar drivers do a 'weird' downshift maneuver... when they downshift from 4th to 2nd they sometimes shift to 3rd first and then 2nd. Any idea why they do that?

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marcucci

Once I FAQ it, it will be closed. No more questions!

Skipping gears can be rough on synchros and gears. Working through the shift pattern helps that. On a downshift there's not much point since you can rev match unless the shift pattern just makes it tough to physically skip gears like that.

FAQ'd.