Downshifting?

[bkreutz]

Double clutching is used on non synchronized gears, what is accomplished is matching the speeds of the gears before shifting. In a synchronized trans the synchro rings and cups accomplish this for the driver. (that is assuming the synchros aren't worn out or broken). Most modern drivers that actually know how to drive a manual transmission have never driven a vehicle that did not have a fully synchronized trans. Older vehicles were a lot busier, then there was that spark advance control mounted to the steering wheel thing.

[disco2hse]

Three pages on downshifting? Really?

Is this a collection of 12-year old girls? Where did you all grow up?

This should be instinctual. You watched your uncle downshifting the hay truck when you were 7. He told you to go fetch it when you were 10 and you made damn sure you didn't screw it up.

If you're an adult and you're asking a bunch of strangers on an internet board how to shift a standard-transmission vehicle, you've lived a sad and sheltered life.

Bit harsh.

Few people today have learned how to drive a crash gearbox. Most over your way seem to only learn how to use two pedals, stop and go, let alone manual gearboxes.

The PO's question is valid and the discussion points out that the issue is not as cut and dried as it may appear inside your own head (which by the way, we can't see).

[Burlsube]

Didn't mean to start a fire fight. I thought the question was legit. It seemed to get a lot of discussion going.

But you’re absolutely right. Driving an automatic car is definitely a commentary on my upbringing. Know what else is? Older men who reply angrily reply to threads on automotive message boards.

Maybe if your uncle still has the tractor you can give me a private tutorial.

Three pages on downshifting? Really?

Is this a collection of 12-year old girls? Where did you all grow up?

This should be instinctual. You watched your uncle downshifting the hay truck when you were 7. He told you to go fetch it when you were 10 and you made damn sure you didn't screw it up.

If you're an adult and you're asking a bunch of strangers on an internet board how to shift a standard-transmission vehicle, you've lived a sad and sheltered life.

[Sputnicker]

I hesitated to jump into this fracas, but couldn’t help myself. It’s a subject that I feel strongly about and I’m hoping I can contribute something positive. It’s clear from the dialog so far that there are some on this forum who would like to understand how to shift their Land Rovers properly. I applaud them for wanting to do it right and there is no shame in not already knowing how. It’s also clear from the dialog that there are some who think they know, but don’t.

I had to learn this stuff as soon as I started driving 40 years ago, when every car I really wanted to drive (or could afford) had at least one non-synchro gear. Down-shifting a non-synchro box smoothly was a right of passage. There were plenty of old-timers around to help with the instruction. It was also a necessity for me because I was slaloming my TR-3 and if I wanted to go as fast as possible and not embarrass myself in front of my peers I needed to master the downshift into first without grinding gears. This required double clutching while heel and toeing (more on that later).

At about the same time I was working as a mechanic in a British car dealership and I saw, first hand, the damage done by those who didn’t understand how to shift properly. By the way, the principles that apply to non-synchro transmissions also apply to synchro boxes and good technique will minimize wear in both. The vast majority of clutch and transmission failures can be avoided with good shifting. I am an advocate for double clutching full synchro boxes too, for reasons that will become evident.

Fundamentally, there are two primary objectives. The first is to match the speed of the engine and the first-motion shaft (aka input shaft of the transmission) before engaging the clutch (taking your foot off), which minimizes clutch slippage/ware. The second is to match the speed of the first motion shaft with the gear you are shifting into, while still in neutral. On a non-synchro gear this will eliminate grinding. On a synchro gear this will minimize the friction and wear of the synchro rings and mating surfaces. By the way the British term for such lousy shifting in our old workshop manuals was “fierceness and snatch.”

While up-shifting, the trick is to wait the right amount of time (fraction of a second), after disengaging the clutch and shifting to neutral, for the first motion shaft to slow down to the speed of the gear you are shifting into. On a non-synchro gear, you know you succeeded if it goes into gear without grinding. On a synchro box you want to minimize the resistance as you shift between the gears. The resistance you feel is the synchro ring trying to slow down the mating gear (or speed it up if you waited too long). If you wait the right amount of time, the resistance will be minimal – and so will the wear.

Once you have up-shifted to the gear you want, the other trick is to engage the clutch smoothly. Again you have to match engine speed to first motion shaft. You control this with the throttle. You know you have it right when the clutch can be engaged quickly without slipping or jerking. Most importantly, don’t mash the gas pedal until the clutch is fully engaged. I think everyone learns this pretty naturally without knowing exactly what’s going on inside the transmission.

Down-shifting is much trickier (which is what started this whole discussion) and requires an understanding of what’s happening mechanically. When you disengage the clutch and shift into neutral the first motion shaft is no longer driven by the engine or another gear and it will start to slow down. However, for a good down-shift you have to accelerate it to match the speed of the lower gear. You achieve this by momentarily reengaging the clutch and blipping the throttle. The engine accelerates the first motion shaft (while the clutch is engaged). Then you disengage the clutch again and shift into the lower gear. This happens in one quick and fluid motion (with practice) and if you did it right a non-synchro gear will engage with no grinding and a synchro gear will slide in with minimal resistance. Once the gear is engaged you have to speed up the engine to match the speed of the first motion shaft. This requires a second blip of the throttle before engaging the clutch. Again, you succeeded if the clutch reengages quickly without slipping or jerking. If your head jerks forward you needed more throttle. If your head jerks back, you needed less throttle.

Now for the cool part. When you have practiced enough to achieve all this smooth down-shifting by use of throttle-blipping and double de-clutching, it’s time to do it while also braking. This is where the heel and toe comes into play. Some people put the heel on the brake and the toe on the throttle and others do the opposite. Pick whichever is easiest for you and start practicing. I know it sounds difficult and it usually takes a fair amount of practice, but it can really help. It allows you to use normal braking and compression braking to full advantage and in a Series Land Rover, you sometimes need all the braking you can get. The last thing you want to do while braking heavily is to take your foot off the brake to blip the throttle. Using the heel and toe you can do both simultaneously. It also allows you to be in the right gear when the braking stops and it’s time to accelerate.

The other benefit to heel and toeing is that you can hold yourself on a steep grade and minimize clutch slipping. There is nothing that will destroy a clutch faster than using it (slipping it) to hold yourself on a grade. I feel physical pain when I see people do this. Some employ the handbrake to avoid this, but heel and toeing is much easier, once you get the hang of it.

These techniques take some practice, but if you are driving an old Land Rover, they are well worth learning. After a while they become second nature. They make driving safer and more fun and they will save a lot of money and grief in the form of worn-out clutches and broken transmissions. No more fierceness and snatch!

One last word on clutch wear. All of this double clutching may result in slightly more wear to the clutch linkage, but nearly all catastrophic clutch failures are caused by excessive slipping and the heat that this produces. These techniques minimize clutch slippage. Most of the linkage is accessible without separating the engine and transmission.

[disco2hse]

But you’re absolutely right. Driving an automatic car is definitely a commentary on my upbringing. Know what else is? Older men who reply angrily reply to threads on automotive message boards

Not certain if this is directed at me. Apologies if it was. But grumpy old men are a reflection on society the world over.

[RoverForm]

I hesitated to jump into this fracas, but couldn’t help myself. It’s a subject that I feel strongly about and I’m hoping I can contribute something positive.

that was excellent! you should teach an afternoon class on this, or at least type it up in step-by-step format.

i'm putting this instruction in my LR "tricks and tips" file.

[ducttape]

I hesitated to jump into this fracas,

Down-shifting is much trickier (which is what started this whole discussion) and requires an understanding of what’s happening mechanically. When you disengage the clutch and shift into neutral the first motion shaft is no longer driven by the engine or another gear and it will start to slow down. However, for a good down-shift you have to accelerate it to match the speed of the lower gear. You achieve this by momentarily reengaging the clutch and blipping the throttle. The engine accelerates the first motion shaft (while the clutch is engaged). Then you disengage the clutch again and shift into the lower gear. This happens in one quick and fluid motion (with practice) and if you did it right a non-synchro gear will engage with no grinding and a synchro gear will slide in with minimal resistance. Once the gear is engaged you have to speed up the engine to match the speed of the first motion shaft. This requires a second blip of the throttle before engaging the clutch. Again, you succeeded if the clutch reengages quickly without slipping or jerking. If your head jerks forward you needed more throttle. If your head jerks back, you needed less throttle.

This was excellent, thank you

If I understand this correctly, it is NOT necessary to actually clutch, shift to neutral, clutch, shift to gear, while going UP, but it is while going down?

David

[superstator]

It is, but it's simpler because you don't have to blip the throttle to bring the input shaft up to speed.

This is just rephrasing Sputnicker, but think of it this way - when shifting down, you're taking the engine from a low rpm to a high rpm. You need to get the input shaft synced up before trying to engage it with the rest of the driveline, so you disengage it (clutch in, into neutral, clutch out), blip the motor to get it (the input shaft) spinning, then shift (clutch in, into gear, clutch out). On an upshift, you're going from high rpm to low. You need to slow the input shaft down, so you disengage (clutch in, into neutral, clutch out), wait a heartbeat for the engine and input shaft to slow, then shift (clutch in, into gear, clutch out). It sounds complicated, but it will become second nature very quickly.

[ducttape]

It is, but it's simpler because you don't have to blip the throttle to bring the input shaft up to speed.

This is just rephrasing Sputnicker, but think of it this way - when shifting down, you're taking the engine from a low rpm to a high rpm. You need to get the input shaft synced up before trying to engage it with the rest of the driveline, so you disengage it (clutch in, into neutral, clutch out), blip the motor to get it (the input shaft) spinning, then shift (clutch in, into gear, clutch out). On an upshift, you're going from high rpm to low. You need to slow the input shaft down, so you disengage (clutch in, into neutral, clutch out), wait a heartbeat for the engine and input shaft to slow, then shift (clutch in, into gear, clutch out). It sounds complicated, but it will become second nature very quickly.

Ok, I got the down shifting thing, but on up shifting, I generally just wait a few seconds (5, 10?) with the clutch in. I don;t consider it riding the clutch at all because at the end of the day it isn;t any great amount of time.

So, my point is, there is no mechanical reason to double clutch on the way up? It's just to make it similar to down shifting?

[yorker]

Didn't mean to start a fire fight. I thought the question was legit. It seemed to get a lot of discussion going.
.

True but the question was really answered by Ike in post #2

http://lmgtfy.com/?q=How+to+double+clutch

It has really reached silly lengths here.

But you’re absolutely right. Driving an automatic car is definitely a commentary on my upbringing. Know what else is? Older men who reply angrily reply to threads on automotive message boards.

It wasn't simply a comment on your upbringing, it was directed at those who avoid downshifting because they are afraid to wear out a clutch or are afraid of messing up the shift. Correct technique for upshifting and downshifting are an essential portion of driving a manual transmission vehicle properly.

Maybe if your uncle still has the tractor you can give me a private tutorial.

A haytruck is a truck not a tractor. Up until ca. 1980 or so if you bought a truck it usually had at least one unsynchronized gear. They were a fact of life as was double clutching. You mastered it by practice, yes there was some grinding of gears in the process and some people are better at it than others. It isn't for everyone. That is why the M135/M211 had an automatic transmission... After having to try to train 100.000's of draftees to drive CCKW's the Army gave up.


Anyway practice, practice, practice, and more practice. Try doing it sitting in a straightback chair in your living room until you have the whole thing down pat- then try it in your Land Rover.

[Burlsube]

Sorry, 1980 was before my time.

Up until ca. 1980 or so if you bought a truck it usually had at least one unsynchronized gear.

[Sputnicker]

on up shifting, I generally just wait a few seconds (5, 10?) with the clutch in. I don;t consider it riding the clutch at all because at the end of the day it isn;t any great amount of time.

So, my point is, there is no mechanical reason to double clutch on the way up? It's just to make it similar to down shifting?

You are correct that there is no need to double clutch while up-shifting (if done correctly). But, it sounds like you are waiting much too long to shift. Generally it only takes about a second, or fraction thereof, for the first motion shaft to slow down to the speed of the higher gear you are selecting. If you wait too long the first motion shaft will be turning much slower than the higher gear.

The duration of the pause varies a little bit with speed, temperature/viscosity of the gear oil, and the ratio between the gears you are shifting between. The timing of your clutch disengaging can also affect it. For example, if you take your foot off the gas before you disengage the clutch, the engine will start slowing down the first motion shaft for that duration. The trick is to practice until you find the sweet spot, which for non-synchro is no grinding and for synchro is minimum resistance in the gear lever (i.e. minimal synchro action).

Once you are in the higher gear, you still have to match the engine speed for the new gear to get the smooth clutch reengagement.

[adkrover]

While I have only read some and not all of the posts here, I have to add my 2 bits and say that downshifting is a very important part in performance driving to just keep the car out of the trees. I have a Porsche 911 that I like to drive on a 5 mile twisty mountain road and if I didn't master the downshift I'd be trimming trees. While it is a synchro box, on a downshift you have to blip the throttle to match the revs or the drive wheels will lock for a micro second and initiate a pretty hairy spin. You couldn't do it only with brakes and a modern gear box can still be driven in different ways.