I think Shopdog is an engineer at BG. We can learn a lot from him.

 

Great thread.....always had trouble in understanding DD...........Have a Merc(auto) with paddle shifters on the wheel and also the facility to upshift/downshift by the side of the stick................so is this Double-declutching business being automatically done for you and by me looking at the rev changes, can learn from this when I drive the Vette?

Did notice benefits when slowing down and not using my brakes, although it still in it's break in period and later read in the manual, not to use this method for the first 1000 miles(Duh!!)

 

Impressive and informative. I'm not stupid (and have stripped and rebuilt my own engine) but transmissions always confuzzled me. Your next assignment: can you explain "heel and toe" shifting in 100 words or less? (Feel free to exceed, I'd just be happy for the info no matter how long it takes...) And thanks.

 

Heel and toe works the same way, except while you're downshifting, you're also braking with the left half of your right foot (assuming the brake and accelerator pedals are close enough together to allow that, if not, then you twist your foot so the heel is on the brake pedal and the toe is on the gas pedal, hence the name).

 

Nope, just an old shop dog who's rebuilt his share of transmissions.

 

AMAZING thread!! Thank you all for the info. I have learned a ton just from this alone especially since my LMB C6 Z51 is the first manual tranny I've ever owned (Hell I'm only 27). The heel toe seems a bit confusing or maybe just a feat (no pun intended) of skill I don't yet posses. Anymore enlightenment on that would be greatly appreciated (ie: when its used, when it helps in racing or just spirited driving). Also is it better to just shift normally at the HP peak while drag racing or to use the double clutch method? (assuming you would be good at double clutching)

 

Some automatics do clutch to clutch shifting with speed matching. That's roughly what we've been talking about doing manually. Others let the torque converter handle the speed change and just bang-bang the shifts without speed matching. Realize that automatics use a planetary gearset that doesn't work the same way a synchromesh manual works. There are no synchros, just clutch packs. Hydraulics engage and disengage the clutches to change gears.

Downshifting just to save the brakes is something big rig drivers do, but it isn't the best idea in a car except in certain specialized situations. Brake pads are cheaper than clutches.

 

Easier to do with filp-flops I'll bet.

 

I'd sold body parts to have a vette at 27!

Just remember to dump the cags and it should be breeze learning the manual.

 

An example of when heel and toe would be used is when you're coming into a turn at the end of a straight on a road course. You need to slow down to make the curve, hence the brakes, but you also need to be in a lower gear to accelerate out of the turn, hence the simultaneous downshifting.

As far as drag racing is concerned, no double clutching or heel and toe there. For the best ET, you'll want to powershift instead. This is rough on the equipment, but it wins races. Right foot stays flat on the floor, and you depress the clutch just enough to disengage the gear, and slam the shifter as hard and quick as you can into the next gear while getting off the clutch. If you're good and quick, it'll sound like an automatic shifting. If you miss, it'll sound horrible, and parts will break. That's one reason I prefer an automatic for drag racing. It never misses a shift, and it shifts quicker than all but the most gifted manual driver. A properly reworked racing automatic will even beat the gifted manual driver.

 

Wanta06,
I already did the CAGS delete, that thing drove me nuts. I didn't have to sell body parts, I just gave up all my free time, work 14 hours a day and stay away from home 8 months per year. Oops sorry I mean I am a Navy pilot We work our butts off and never have time to spend the money, so I bought the vette (its my only car though). However I do love my vette and am having an absolute blast in it for the short time I am on solid ground. Thanks for all the great info on these driving skills.

Shopdog,
You are nothing short of a genius. I have read a ton of posts where you have saved the day, and thank you for all your inputs. Even when we all ask stupid questions you always take the time to answer them. So thank you.

 

Re-thanks!

 

The manual says that because people are idiots and they don't know how to downshift right. Match the gears, I double clutch to be extra careful.

 

There are a number of items in the owner's manual that do fit in the 'driving for dummies' catagory, like 'Don't remove roof panel while driving', but this downshifting item doesn't qualify.

I have been driving manuals for 20 years and have been 'downshift right' without having to match gears, or double clutching since the 4 and 5 speed trannies that I've been driving don't require it. Granted, I am not all knowing as some of you 'professionals', but I don't think that I fit in the idiot catagory either.

The downshifting one gear at a time statemant in the owner's manual is good advice for those that have not learned the more advanced techniques of RPM matching and double clutching. IMO

 

The last problem is a little more significant. I've noticed three times now when I'm slowing so rapidly I need to shift from 5th or 6th to 2nd that the gears grind if I go directly into 2nd. I think I have a sticking synchro but I don't know enough about transmission to really know. This happened the third time as I was leaving Jumper so I called back and they will look into it when I return for the steering reservoir repair. Any comments from the experts?

John[/QUOTE]

John, you got some excellent information from shopdog and the 'whitepaper' that stannh submitted. Yours is a common question from younger dirvers (I have to laugh when I read posts that say NOBODY double clutches anymore, or that you don't have to 'blip' the throttle when doing so). Here's my .02c on advice for anyone who wants to learn.

Downshifting with double-clutching has to be a smooth, unconcious act, not one you think about or memorize rpms, or even look at your gauges. If you do, you'll spend too much time thinking and not doing! Kind of like trying to remember every golf tip you've ever heard and trying to hit a ball while thinking about all of them. You have to get a feel for the machine you are controlling, gear spacings, the sounds. Try this:
1. Just get in the car (unstarted) and simply practice stepping on the clutch twice in rapid succession.
2. Now go drive on a lonely road.The idea is to 'time' your clutching such that the gear shift lever is coming through the neutral gate when your foot is up. Try it slowly and smoothly at first, no hesitations, then as you become more proficient, everything (except the car) will speed up.
3. Gets trickier now. At the same time, apply a little throttle pressure in anticipation of what engine speed you will need for your intended gear and speed. This is hard to learn and has to become instinctive if you are ever to be smooth. (missing your rev mark and rapid clutching will break traction, and in traction-poor conditions (exactly when you need to be most smooth), you wheels will break away from the jolt (either too fast or too slow). Practice, practice, practice (after about 40 years you'll get it, lol).

I agree that it is not so necessary now with modern competent cars, especially when the gear spacings are so tight with the more common six speeds. I still do it out of habit. With such tight spacing and good brakes (see heel and toe later), I am often tempted to skip shift down because it is hard to make three or four downshifts (even if you are only single clutching) in the time it takes while also slowing with the (great!) brakes.

OK, so you've learned how. Now comes the really hard part, learning how to heel and toe. If we had three feet (or you are VERY well endowed and VERY talented), you wouldn't need this. Very often, you need to slow more quickly that just by engine braking (you should be fully engaged and letting engine compression slow you, NOT clutch slipping!). So you need your brakes too at the same time. Now it becomes a choreographed dance on the pedals. I find in the Corvette (nice pedal spacing) that I used the middle of my right foot on the brake, and roll the right side of my foot onto the throttle. Other cars require different positions such as toes on the brake and heel to the throttle (use what's comfortable for you).

So now as you approach that tight corner in 5th and need 3rd, your left foot will be going down and up 4 times in rapid succession, you will be modulating brake and throttle with your right foot. Note that in this case, you will need less 'blip' because your road speed is diminishing so rapidly. Your hand will be pulling the gear level through the neutral gate on the first and third clutch cycle, and increasing engine speed for the upcoming 2nd and 4th clutching cycles. I know this sounds almost impossible to master, but it really does become second nature with practice, and in the end you will be a much smoother driver, with better car control and less wear on your car (although you may eat everything up just learning!). I have often been told by surprised passengers that they didn't realize I had a standard because the transitions are without the annoying forward or backward jolting you get when RPMs are mismatched, either up or down (not necessary to double clutch or heel and toe to be smooth, but it helps). Dammit, I can't even get very rapid, high-rev upshifts right yet with this monster car: I'm beginning to see what others have said about the clutch pedal engaging too late. I either have to adjust the clutch or me!

Last note on semantics: "De-clutching" is actually correct, just not used in the general vernacular. When something is "clutched", it is held fast, as in "grabbing' or holding tight. So your car is "clutched" when the pedal is UP and "de-clutched" when DOWN. In language, when something is cumbersome, it is quickly changed, even if the opposite is the true meaning. We say "string beans" for what is actually "stringless beans", we say "pitted olives" when we mean olives without a pit. We even invent opposites, as in "bad" meaning "good".

I still think I suck with this car at 1500 miles and it will take me a long time to feel that I have it right and am using this machine at anywhere near its capabilities (slow learner I guess, lol). OK I'm done now, guess that was more than .02c.

George

 

Great post with a lot of information. This might explain why I hear funny noises when I downshift into 2nd at 80;shrug. On the heel and toe if you are going to try it I would suggest that you practice in a parking lot before hitting the high speed curves;W