Making Best Use of The Gearbox

The gearbox of a motor vehicle is a sophisticated piece of machinery, the component parts of which all work in harmony. It is designed so the driver can get the best possible performance from the car engine no matter what the driving conditions.

It’s All About The Right Gear For The Right Job

How you use your gearbox will make a very big difference to how effectively, or otherwise, you will make progress along the road. Change to a high gear too early, during the acceleration phase, and the car will judder and struggle to pick up speed.

Hold a gear for too long as you climb the rev–scale and you will pass through and beyond the point at which maximum power and torque is delivered. This results in the engine thrashing away and not actually getting you anywhere very quickly, as well as causing accelerated wear so things may break.

Using the gearbox ratios intelligently can make a big difference in the way a car behaves. Holding a mid–range gear through a series of bends, for example, is a technique used to maintain a higher level of control and to facilitate a smooth and flowing drive.

Early on, Cars Had Big Engines, But Small Power

When cars were first made they were by today’s standards quite primitive machines. 4.5–litres in the 1940’s only produced a fraction of the horsepower that a 4.5–litre engine produces today. In fact, the modern 1.2–litre runabout would probably outrun one of those old big–engined bone shakers, and 4.5–litres was quite modest back in the 1920’s.

By the time cars were made available to the masses an engine size typically would be no more than 1,000cc’s. As the cubic capacity rating relative to power output then was low by the standards of today, manufactures had to gain the best from their meagre output by implementing an appropriately gauged range of gears. As a consequence, the gear ratios were fairly low and closely spaced, and as the price of fuel was about 3p per litre, it didn’t really matter. Economy then was not the main consideration.

Then came the five–speed gearbox

By the 1970’s the British car buyer was introduced to something quite new — the 5–speed gearbox. This was seen as big advantage and it was not long before all manufactures began to follow suit. The Austin Maxi, built by British Leyland, was not only the first hatch back car to hit the market, but also the first British built car to have a 5–speed gearbox. However, whilst this suited the 1750cc Austin Maxi, it was a different story if you had one with the alternative 1500cc engine.

The 1500cc Austin Maxi actually produced insufficient power output to sustain road speed with top gear selected, which rather defeated the point of having a fifth gear as a top gear in the first place.

Moving forward to the modern day cars, the concerns of the vehicle manufacturer are now somewhat different.

Nowadays the effect of the internal combustion engine upon the planet is a big issue, and with oil prices being more volatile than ever, certainly fuel economy, coupled to low emissions, has become very important. Yes, we all want to get that extra couple of miles out of a litre of the stuff, that’ for sure.

As automotive technology has moved forward
we have to adjust our driving style

Also, because the torque range of modern engines is wider, and the gearing has become higher, it means that the choice of gear for the driver, in response to a given situation, will need to be thought out differently.

Take a very popular type of family car as an example, perhaps the 2009 edition of the Ford Focus 1.8 Turbo Diesel. Where as a car 10–years older would be quite content to be driven at 30mph in 4th gear, this Ford Focus is not. Therefore, the driver needs to use third gear instead of fourth for this speed.

There are many other makes of car that are the same where this is concerned, so we are not trying to make a poor example of the Ford car. It is not the fault of the car, but it means times have changed and we have to adapt ourselves to a different way of driving.

Using 3rd Gear in 30mph Speed Limits is a Good Technique

So, what is the harm in using third gear for 30mph anyway? For many it will seem odd to do so, but where does it say, “Thou shalt always arrive at the top gear in the gearbox when driving your car down the road?” We have known of people whose standard practice was to drive at 30mph in 5th! Yes, it does make you wince doesn’t it.

Gears are there to assist you to gain the best out of a car in terms of driver flexibility, and in any case, using third gear for 30mph is a good speed limit compliance technique anyway, as it helps not only to remain within the speed limit, but allows greater drivability.

If You Are in A Gear Too High You Will Waste Fuel

There is no doubt there will be those who will try and argue that not changing to top gear at the earliest possible opportunity during the acceleration phase is wasteful on fuel. This is actually not always true, and we can explain this by using the good old pedal cycle as a model.

If you were to try and ride a bicycle with the idea that you have to reach the highest available gear in the shortest distance travelled you would soon change your tune, because it would be you and not an engine having to work harder than necessary. Struggling to heave the pedals around would make you very tired very quickly.

Thinking of riding the bike, in what way would you ride so as to expend the least amount of effort, but still make the best progress?

The answer would be to ride with your pedals moving at a moderate speed and with sufficient momentum that is comfortable so as to sustain your road speed, even absorbing minor changes in gradient without you really noticing. This would be a speed you could maintain over a prolonged period without having to heave the pedals around, or conversely, have your feet whizzing so fast you couldn’t keep up with yourself.

Less energey output requires less fuel input

The same applies to a car engine. That Ford Focus is far more comfortable doing 30mph in third than in fourth, and requires less energy to sustain that speed in third gear. If it is achieving this with the least amount of effort being used it is using less energy, and therefore less fuel, and there is less stress on the machinery to achieve it.

Also, by use of third gear in those circumstances, the driver will more easily be able to make the necessary changes in speed to meet the requirements of driving in traffic, easing or squeezing the accelerator, which often removes the necessity to brake.

As well as making it easier to keep the car within 30mph, as we have said, it also makes up and down gradients easier to drive as it removes the need to make further gear changes, and again reducing the use of the brakes.

Braking Represents Wasted Energy

If you are not braking you are reducing the amount of wasted energy, and if you are not wasting energy, you are saving on fuel, tyre wear, degradation of brake components and other service parts. Not everyone drives a Ford Focus, and whilst each model of car will have its own gearing characteristics, all will manage to be comfortable when being driven in 3rd gear at 30mph.

Driving in town is not the only place where third gear helps produce a smooth and flowing drive. Imagine you are approaching the end of a 30mph zone and about to drive into a National speed limit area. Using the road shown in the diagram below as an example, after travelling along a short straight section there are two bends, each separated by another short straight. After the second bend there is a fairly straight road, and for about half a mile.

Learn to Ease and Squeeze For The Perfect Balance

	By remaining in third gear from the 30mph speed limit area, you can accelerate smoothly, crisply and comfortably to an appropriately greater speed. Still holding the car in third. As you approach the first bend you begin to back off the throttle at just the right time, so that
when you reach the bend, the car is travelling at the desired speed at which to drive that bend. As the appropriate gear for the bend is third you can now balance the car on the throttle for the duration of the curve with just enough power to keep it pulling, but not accelerating. Then, by squeezing the accelerator, and using that same gear, you can drive the car smoothly out of the bend and onto the short straight. Seeing the next bend ahead, and still holding the car in third, you begin to ease off the pedal, decelerating for the second bend that comes up shortly after the first. Using the same technique as with the first bend, you keep the car under drive as you negotiate the curve, squeezing in the power again on the far side. Now on the longer straight section it becomes more appropriate to use the higher gears, changing up to fourth, and even fifth, as required. Easing and squeezing the accelerator like this, when in tune with a winding road, is such a satisfying way to drive.

What you will have used here is a technique known as acceleration sense, which is best described as the ability to vary the speed of the vehicle in response to changing road and traffic conditions by use of the accelerator, often removing the need to brake.

This, in combination with the effective use of the gearbox, can produce a brisk, yet smooth and flowing drive that will be achieved with the maximum degree of control, and with the least amount of stress being placed upon you or the vehicle.

It is amazing how so many people find it so hard to change to a lower gear without applying brakes, unless they are climbing a steep hill.

Changing Down Without Slowing Down

It is often desirable, for the sake of maintaining tighter control over the vehicle, to select a lower gear, but without taking any loss in road speed. An example of an occasion where this method may be used could be that of driving through a cross road junction, where although you have priority, you may wish to prepare for the unexpected by driving in a more responsive gear. In this case, once the junction is cleared, and there are no further hazards, you can return to your cruising gear whilst maintaining your speed throughout.

Drive a third gear bend in fifth and the car will feel like a lump of dead wood. Drive a third gear bend in third gear and the car becomes alive and eager to deliver, and your fuel consumption doesn’t actually suffer.

Julian Smith
Ride Drive Limited

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Part–1 Making Best Use of The Gearbox
Part–2 Making Smooth Gear Changes
Part–3 Get More From Automatic Transmission

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This page was last updated
Thursday, 27-Jan-2011

Getting The Right Gear Will Produce a More Controlled Drive