tkx

Hey all,
Is it just me, or does the TL not need double clutching?... I have read a few posts here about people talking about double clutching, but in my own experience I found that I don't need to double clutch to get a smooth transition. I'm asuming that the transmission in the TL is a synchromesh transmission...

Anyways, just saw posts on the site about this, and was always curious why people here are double clutching with a synchromesh transmission. Then again, I'm not too sure if the TL has a synchromesh transmission .

Any1 know?.

Champcar1

It is a syncromesh transmission. No need to double clutch.
By the way, I see you are from Edmonton. Are you aware of the race coming to your town next year? Hope you are and I hope you can make it. If not let me know and I'll fill you in a bit on what's happening.

tkx

No, I do not know of the race coming to Edmonton ;P. Please do let me know.

Also, thanks for clarifying that it is a synchromesh transmission. I was SURE it was, but then people were talking about double clutching here and I got confused.

Champcar1

It's July 15-17. Rather than waste everyones time just go to www.champcarworldseries.com or www.edmontonchampcar.com and check it out.

zax123

OK I've got a weird question. I've noticed something. When I clutch before shifting in the TL, it seems to me that the RPMs stay pretty high and don't drop down as fast as on my other MT cars. Since our car is a drive-by-wire throttle, I was thinking that maybe the ECU gives the engine a bit of gas just after you clutch in order to keep the revs up and make the shift smoother. Am I crazy or the car actually doing this?

SouthernBoy

If by double-clutching (in your vernacular), you are referring to rev-matching, then by all means, you DO want to do this when downshifting.

You see, most people who drive manual transmissions do not know how to properly downshift. What they do is: 1) remove their foot from the throttle; 2) shift the transmission into their chosen lower gear; 3) begin to slowly release the clutch without depressing the throttle.

Do you see the several errors here? Do you see how bad this practice really is?

pettydw

Heel and toe is sufficient for fast downshifting of syncro transmissions (as in TL) in most cases. Double clutching is not necessary unless the syncros are out to lunch (very cold or worn out).

The TL throttle is held partially open after you lift off the pedal, mostly for emissions reasons though it does help shifting in most instances. Most all cars are this way now, with the domestics jumping on this technique 10-15 years ago.

zax123

How could you keep the throttle open if the car wasn't drive-by-wire?

Champcar1

Absolutely correct. You do not need to double clutch. Rev matching on the downshift is different than double clutching. And heel-toe is something that must be practiced a lot to get good at. And do not do it in traffic until you are very good at it.

6mtV6

Only time I double clutch or rev-match is when i'm downshifting.

JoganJani

Me too. While upshifting TL does a good rev matching if you keep clutch pressed for a second longer than usual.

SouthernBoy

There is no need to rev-match during an upshift as it's a normal part of the process anyway.. the RPMs are dropping as you get into the higher gear.

However, in order to properly downshift, rev-matching (double-clutching) is an absolute must. There is really no other way to do this.. remember, I said proper downshift.

Here's something for you to read. It is a collage of things I wrote on another website.. hope it helps and explains things.


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Note: As it says, this is a collage of various postings I have made over the past one and a half years on the altimas.net website. So you are likely to see redundancy as well as a few other items of disarray. But enjoy and I hope you learn something.




PROPER MANUAL TRANSMISSION DRIVING TECHNIQUES

What follows is a collection of writings which I have posted at various times on this website in an effort to help answer some questions regarding the proper manner in which a manual transmission should be operated. While there are certainly many ways to drive a car with a manual transmission, there is really only one correct way. I was most fortunate to have learned these techniques while I was still in my teenage years. In so doing, I was able to avoid developing entrenched habits before they became really bad habits and difficult to correct. It is my hope that this helps you learn what I have learned and perfected over the years. If you do, you will reap the rewards, both financial and in the knowledge that you have mastered a technique that few do in their lifetimes. Have fun!

Under normal driving situations (not racing), when you start out from a standing start, you do so with the lowest possible RPMs, get the clutch out to full engagement as soon as you can while adding throttle. If you do this correctly, the transition will be smooth and seamless, and the wear on your clutch disk, pressure plate, release bearing, and flywheel will be minimized.

If properly designed (sufficient size and clamping pressure, etc.), and properly installed with no defects (correct torque, non-faulty equipment, alignment, etc.), then the next, and most important, factor to the life of the clutch assembly is the operator.

THERE IS ABSOLUTELY NO REASON WHY A CLUTCH CANNOT LAST THE LIFE OF THE ENGINE UNDER NORMAL DRIVING CONDITIONS.

When I speak of engine life here, I am referring to life before a serious teardown or part replacement such as a timing chain (200,000+ miles) or headwork. If you cannot get at least 100,000 miles out of a clutch, you are doing something terribly wrong. Obviously, racing and other extreme conditions such as towing constitute a whole different approach and, as such, do not come under this.


Don'ts:

Do not use any more engine speed (RPMs) than absolutely necessary to get the car rolling in first gear.

Do not hold the car on a hill with the clutch.

Do not wait for a traffic light to turn green with the transmission in gear and the clutch depressed.

Do not rest your foot on the clutch while driving.


Do not ride the clutch in any gear (obviously you will to a small degree in first to start off).

Do not down shift by just removing your foot from the gas, moving the shifter into a lower gear, then releasing the clutch slowly.


Do's

Start off smoothly and with low engine speed, and shift in such a manner that if you had a passenger on board, they would not even notice the shifts.

Hold the car on hills with the brakes.. that's what brakes are for. NEVER hold a car on a hill with the clutch. The amount of heat generated by doing this is incredible.

While waiting for a light to change or while sitting in heavy traffic, put the transmission in neutral and get your foot completely off of the clutch petal. Leaving it in gear for extended periods heats up and shortens the life of the release bearing. The normal condition of a clutch is fully engaged so it stands to reason that's where it should be most of the time.

Resting your foot on the clutch petal while driving engages the release bearing.. see above.

Avoid riding the clutch as much as is humanly possible. You will extend its life significantly.

If you do not know how to properly downshift, DON’T. Use the brakes (should do this anyway), and avoid downshifting any more than necessary. Improper downshifting is analogous to riding the clutch because that is what you are actually doing. Learn how to properly downshift first and save yourself the frustration of premature clutch failure.

Clutches are wear items, heavily affected by heat caused by friction. In a front wheel drive car, they are costly to replace, so unless you like shelling out a lot of money periodically for the replacement of these components, learn the correct way. Learn it until it becomes second nature like breathing.



I spent some time teaching a lady with whom I worked 10 years ago these techniques when she purchased a new '92 Honda Accord LX. When I last spoke with her, she had well over 140,000 miles on the original clutch with no signs of slippage. So I'm not jerking anyone's chain here. Learn to operate a manual transmission correctly and you will reap the rewards by saving a lot of money. Plus you will be one of the few who know how to do this right.

I don't mean to set myself up here as some kind of guru because I am not. But I have been driving vehicles with manual transmissions for over 40 years. I have spent the time to perfect the process into an art form because when done correctly, that’s what it is. When I sold my '88 Mustang LX 302CID, it was 6 years old and had 77,000 miles on it. When the buyer drove it, he asked me when I replaced the clutch because to him, it felt very positive. I told him that I had never replaced it and that it was the original unit. I added that it wouldn't make any sense to replace a clutch after only 77,000 miles since that is not very much wear. He had a little bit of a hard time believing this, but he did buy the car. Three months later, he called me up to let me know how much he liked the car and to tell me had had not wrapped it around a tree. He again asked about the clutch and I again told him that it was the original clutch.

I used to own a 1966 Chevelle SS396/360HP. I was the original owner of the car. For a period of about 2 years, I was street racing the car frequently on the weekends. At 83,000 miles when I sold it, it would still break traction in all four gears and the clutch had no slippage. It was tight and strong. Now granted, American cars have traditionally had stronger clutches than Japanese cars. This is changing because the Japanese are putting larger and stronger (torque) engines in their cars.



Downshifting

Ah yes, downshifting. If I had to name just one facet of manual transmission errors-of-operation, this would probably be it.

To understand how to operate a manual transmission, you have to know how the clutch assembly and transmission work, and I am going to take the assumption that most do on this forum. I will only clarify synchronizers. They serve to match the speed of the gears in the transmission as the shifter is moved to a given gear. Now for downshifting.

Let's say you are in fourth gear and you are approaching a stop sign, so you decide to downshift from fourth gear into third. What most people do is just remove their foot from the throttle, depress the clutch while moving the shifter from fourth to third, then start releasing the clutch slowly until they achieve full engagement. If you do this, what you are actually doing is riding the clutch in third gear. After all, the engine has returned to idle (or close to it), you get into third, then just ease the clutch out which pulls the engine from idle up to the RPM's at which it will operate at whatever speed you are traveling in third gear. Here is the correct way to do this in steps that I will break down in a moment.

Raise your foot off of the throttle.

Depress the clutch.

Start the shifter up into third.

As you pass through the neutral gate, let the clutch out a bit (doesn't have to be all the way) while at the same time blipping the throttle to increase engine speed BEYOND that which it will operate in the chosen lower gear.

Depress the clutch again.

Engage the chosen lower gear.

Let the clutch out while adding throttle.

As the engine RPM's decrease they will be met by the engaging clutch and opening throttle.

This should be a simple, smooth, fluid motion and you will know you've done it right if there is no jerking as the clutch comes out in the last step. Now for some details.

As you move into the neutral gate with your foot off of the throttle, the engine RPM's will be returning to idle. This is the point at which you want to blip the throttle a bit while at the same time engaging the clutch some. You want to get the engine turning faster than it will when you are in the lower gear you have chosen. The reason is that you want to spin the gears up to a speed that equals that at which they will be operating when you finally release the clutch in your downshift. If you do this right, there is no clutch slippage because the engine and the gears in the transmission will be spinning at the same or nearly the same RPM's. No slippage means you will get into gear with full engagement of the clutch sooner and with virtually no wear. To best understand this, you really need to know how a clutch assembly and transmission work together to deliver power from the engine to the drive wheels.

This takes a lot of practice, but if you get it down, you will be heads and shoulders above just about anyone else who drives a car with a manual transmission. You will begin to notice the mistakes other are making when they drive. Learn from their mistakes and it will both save you money and make you a far better driver.

So it's in with the clutch, start the shifter into the chosen lower gear, while passing through the neutral gate, blip the throttle and at the same time engage the clutch a bit to spin up the gears, then back in with the clutch as you get into the chosen gear, then finally release the clutch in one smooth operation.

Here's another little tip. Say you are waiting at a light for the green and your transmission is in neutral like it should be with your foot completely off of the clutch petal. When the light turns green, instead of just depressing the clutch and pushing the shifter up into first, pull the shifter partially into a higher gear first, such as second or third. The gears in those selections are not spinning as fast as the gears in first. By starting the shifter into a higher gear before you go to into first gear, you will cause less wear on the synchronizers and they will last far longer because they do not have to stop gears which are spinning at a higher speed. For cars which do not have synchronized reverse, definitely do this and you will not experience the grinding affect when shifting into reverse.

Say you are driving normally, shifting up through the gears to the one in which you wish to be for cruising. As you disengage the clutch and move the shifter to the next higher gear, you might notice a slight resistance just before you finish the shift. What you feel is the synchronizer for that gear forcing the drive gear(s) from the input shaft and the gears selected to "mesh". That is to say, their speeds are forced to equalize so that as they engage, there is no grinding and no damage to the gear teeth. That said, we can move to double clutching.

Double clutching was a technique that came about when earlier manual transmissions did not have synchronizers. If you did not double clutch, you would experience some serious gear grinding when shifting.

If you did not have synchronizers in your transmission, you would have had two choices when shifting gears: (1) put up with some really serious grinding and damage/breakage to gear teeth, or (2) manually match the speed of the gears in each selected shift so that you would eliminate the problems just mentioned in #1.

Suppose you are traveling in second gear, the engine is turning at 2500 RPM, and you are getting ready to shift to third. At the road speed you are going, let's say that once in third, your engine would be turning at 1800 RPM. When you remove your foot from the gas, the engine is going to loose RPMs quickly and by the time you get into third, the engine might only be turning 1200 RPM. Without synchronizers, you would need to raise the engine back up to 1800 RPM in order for the gears to mesh. By blipping the throttle and at the same time letting the clutch out some when you are passing through the neutral gate, you will both increase engine RPM and increase gear speed. As the engine RPMs fall back off, they will reach a point at which you will be able to complete the shift.

Since for years, manual transmissions have been fully synchronized, there is no need whatsoever to double clutch when upshifting and I definitely recommend against this practice.

Now downshifting is much like this, only in reverse. In other words, you are going from a higher gear to a lower gear so if your engine was turning at 2500 RPM and you wanted to shift to second, You would want to blip the throttle enough to raise engine speed to perhaps around 3200 - 3500 RPM.

When you are upshifting, the RPMs fall off and most people find it pretty easy to adjust to this and to add throttle at the right time so that when the clutch comes back out, they have the proper RPM's for the gear selection/road speed.

However, most people downshift by (1) removing their foot from the throttle, (2) moving the shifter into the next lower (or chosen) gear, then (3) slowly releasing the clutch while adding little or no throttle. This is NOT the proper manner in which to downshift. What you are doing in effect, is riding the clutch in reverse. In other words, you probably wouldn't dare attempt to start your car off in third gear because you would have to add a lot of throttle and really slip the clutch to get the car moving. When you downshift like the example I just gave, you are doing something similar to starting off in a higher gear, though it does take more energy to get a car moving from a dead start. Now if you double clutch during the downshift, you are spinning up the gears and the transition to the next gear will be quite smooth.


Junkyard asked a question about the concept of “passing through the neutral gate”. You don’t stop or stay in neutral. You are just passing through, so to speak. In your second question, you said I had mentioned to put the car in neutral when downshifting. Not exactly. Try this with the engine off.

Put the car in fourth. Depress the clutch and shift to third and let the clutch out. Now do the same thing, only this time as you pass through the neutral gate, let the clutch out some or a good deal and blip the throttle, then clutch back in, get into third, clutch comes out for the final time. That is the movement you want.

Incidentally, blipping the throttle is just a little stab at the petal, enough to raise RPMs to the desired level. You do not want to be on the throttle long because you will be in the process of shifting. Yes, this does take a lot of practice and may not come easily for many, but it is the best way, in fact the only proper way, to downshift because it very significantly reduces clutch and synchronizer wear (especially clutch), and once you get the hang of it, you will be able to do it quite fast.

The bottom line to all of this folks is to match engine speed to wheel speed in a given gear, and to do it in such a manner as to eliminate undue trauma to your drive train. I do this all of the time and have been downshifting like this since my late teens. I actually learned it from a magazine article (as I can best recall). If you know how a manual transmission and clutch assembly operate, all of the components and how they perform together, you will understand the beauty of the process.

Oh the grinding noise Junkyard hears when he starts letting up the clutch too quickly is most likely due to not having fully engaged the gear teeth and they separate (pop out of gear). That or he actually begins engaging the gear teeth before the clutch is fully depress so there is still some flywheel/disk/pressure plate contact.


One of the things I noticed right off the bat on my SE was that the clutch began to engage much too close to the floor for me (a contributor to the problem Junkyard has had). It was starting to engage about 1 inch from the floor, so I adjusted it out to 2 inches and it is fine. If you do this, just make sure you have the required toeplay, otherwise you will prematurely wear out your release bearing.

The purpose of letting the clutch out some as you pass through the neutral gate is to spin the gears up in preparation for the speed at which they must be at for the lower gear selection. This will allow you to get into that gear very easily. When you depress the clutch, you disengage the crankshaft from the transmission. The gears in the transmission will begin to slow down. By letting out the clutch some (or completely) in the neutral gate, you once again, MOMENTARILY, engage the full drive train and get the gears spinning. Only this time since you have blipped the throttle, they'll be spinning faster. As they slow down from the higher speed, your clutch will be coming out for the final time with the transmission in gear and the mesh will be smooth.

Try it both ways. Do it first the way you do it and notice that you have to add a little bit of force to get the shifter into gear. That's because the synchronizers are doing their job of gear speed meshing. Now try it the way I outlined and if you do it right, you will have virtually no resistance as you slip the shifter into your chosen gear.

Instead of going right into first as the light starts to go green, try starting the shifter into second gear.. don't have to go all the way into gear, though it won't hurt. This slows the gears down just as though you had gone on into first, but it's much easier on the synchronizers. And you won't get the "crunch" you mentioned when you have to move quickly.


To prevent rollback; practice, practice, practice, practice.

One way to do this is to find a nice little hill someplace where you won't be a bother to anyone. Take along some masking tape and mark off two sections with the tape a foot apart. Your goal is to keep the car from coasting back more than 1 foot.. of course you do not use the clutch to hold the car.. use the brakes. As you learn to do this, find another hill a little steeper. And so on, and so on.

rontatuaf

Zax, a solenoid is often used to delay throttle closing.

spidey07

necessary? No.

But i do it all the time just for fun sake.