Fastlane

At 80mph or above my synchros are not happy with me. Am I just being stupid? If so, what's the "happy" shift point in MPH when going from 4th/6th to 3rd?

thx.

Fastlane

Come on, help a poor Texas boy out!

TTT

LTC Z06

Are you trying to rev match for a clutchless sift? Forget it, just down shift then blip the throttle before letting off the clutch.

Fastlane

Actually I'm not doing a clutchless shift at all (missed that part in your response).

I'm simply downshifting from a high gear into 3rd gear at around 80mph, syncros don't like it and I hear it. 70mph seems to work just fine.




[Modified by Fastlane, 6:22 PM 8/18/2003]

C66 Racing

What he is referring to is blipping the throttle when you downshift to match revs. At that speed, 3rd will be a couple grand higher than 4th, so if you blip the throttle 2000 rpms while the clutch is in and then let out the clutch you will barely notice the downshift (other than hearing it). This is the starting point for toe heel downshifting while braking.

Fastlane

I know what he's talking about, syncing the RPMs with the level I'll hit when I downshift to 3rd. What I'm concerned about it the noise I'm hearing when I downshifting to 3rd at 80mph. If that's too high downshift with having to synch up the RPMs then cool, that's all I needed to know. If not, then maybe I need to keep an eye on this. I'm just looking for current Z06 owners to confirm this one way or the other.

SWCDuke

I've been double clutch downshifting for 40 years - proper double clutch downshifts, not just blipping the throttle and indifferently jamming in into a lower gear, which places HUGE strain and wear on the synchros.

In the same time period I have NEVER had to replace a synchronizer despite racking up over 100K miles on several cars including SCCA racing and road course hot lapping, sometimes with gearboxes that had a "bad" reputation.

Reading how Phil Hill drove a race car in Road and Track back in the fifties was my "driving school", and it's still paying dividends. Take care of your car and drive it with respect, and it will take care of you.

Once you understand what a synchonizer is asked to do in a fraction of a second downshift, you will understand why double clutching is an essential part of spiritied driving if you want the hardware to last. The noise you hear is the synchronizer crying out in agony.

And to those of you who say "professionals don't do it", I will remind you that "professionals" don't have to rebuild their own gearboxes, and guys like Mark Donohue, who were easy on the hardware, usually finished the race - and were on the podium.

Duke




[Modified by SWCDuke, 6:49 PM 8/18/2003]

Fastlane

That's good information, but it still doesn't answer the fundamental question. Is 80mph too high to downshift into without doing some sort of mojo with gas pedal and clutch?

ztheusa

ANY speed is too high to downshift smoothly unless you get off your butt and learn how to double clutch.

Simply stated, you are only half way to driving till you can double clutch.

You kids!!!!!

Michael Joslyn

I don't think 80 is too high as the gear tops out at 101 but you need the mojo. Having said that, 5and 6 to three are tough shifts for me to make without seeking 4th first. In any case, there is a cosiderable amount of spindown on the syncro when doing this shift if you are refering to the whine you might be hearing. I do blip the throttle and it helps but honestly it's a touchy shift in my car that requires a very confident and positive engagement, especially since this is a passing gear operation and I'm flooring it while the clutch is comming up. I don't even attempt a 5or 6 to 3 directly anymore. It doesn't matter how I blip or how hard I push, it will grind. As for smoothness, just remember (I'm sure you know this) if you have to come up 2500 on the blip you need to then bring your RPMs up again quick to that running RPM as the clutch comes out or it will be a rocking shift.

LTC Z06

You should always do something, either double clutch or blip so as not to lock up the rear tires and put a strain on everything.

Fastlane

Finally, yes!

That is exactly what I wanted to know - thank you!

(in regard to the "You Kids" comment - been driving for 26 years, not racing)

:steering:

Chuck Harmon

SWDuke said it right. For me, the challenge and mastery of down shifting and up shifting so smoothly that you hear the gear change but don't feel it is what makes driving a stick so much fun. An occasional power shift (which is with the clutch but right foot glued to floor) makes those special moments a bit more thrilling. There's really not much else to do at street legal speeds. A car that can shift without me makes me feel that I'm not needed! :sad:


Regarding what is too high a speed to downshift to, I wouldn't downshift to a gear that is much higher that the speed the next lower gear would safely go. So if I shift from 2nd to 3rd at about 75, shifting down to 3rd at a speed above 80-85 is of doubtful benefit. Downshifting for only 1000 rpm left in that gear would be a waste of time unless you were running close to 200 mph.

But if you do downshift without proper double clutching at such extreme rpm differences between the gears, your tranny will not live very long. It also tends to hurl you, your passenger, and your coffee through the windshield
:banghead:

Chuck


[Modified by Chuck Harmon, 8:00 PM 8/18/2003]

BIG LAW MAN

Double clutching takes too long and it is basically the same thing as heel toe downshifting without the added step of putting it in neutral and hitting the throttle to match RPM as you then down shift.

ruking1

SWC Duke summed it up. The best and least stressful to your systems is Double clutching or as the English refer to, double de clutching. If you are going to be doing a lot of 5th/6th downshifting to 3rd, as a BARE minimun blip the throttle. The best is to double clutch. The other important car handling issue is if you miss a shift or get bogged down etc.,You really dont want to be inadvertently changing the weight and handling balance at any kind of speed.

When I am on the road, for passing, I do a lot of 5th/6th downshifting to 4th.(third sometimes in the twisties) It is as smooth as glass only because of double clutching. I would argue in favor of your syncros. If you are going to just blip the throtte is is not too far a stretch to start to do a proper double clutch.





[Modified by ruking1, 8:30 AM 8/20/2003]

SWCDuke

You're clueless!

Duke

Chuck Harmon

An automatic really is a better choice for many drivers.

Chuck

BIG LAW MAN

Yeah and we ALL know how smart you are. :rolleyes:

ruking1

That might explain why fully 65% of Corvettes are automatic :boxing

Timz06

can someone tell a poor brotha like me the steps involved in a successful double clutch shift?

thanks