Gearbox

The Gearbox

Gears are also called cogs – metal wheels with teeth on the edges. When these are put in contact with each other, one can turn another. The gearbox is quite literally, a box of gears turning each other. It’s part of the transmission, the link between the engine and the wheels. The gears are of different sizes so that controls the relationship between the engine speed and the speed of the road wheels.

First gear, for example, is the most powerful gear since a small cog (from the engine) is turning a large cog (to the wheels). This means that the engine runs fast while the wheels turn slowly.

Fifth gear, on the other hand, has the opposite effect. A large cog (from the engine) turns a small cog (to the wheels). So the car travels fast while the engine turns slowly.

This is why you need to come off the gas during a gear change. You are slowing the gearbox down, so you need to slow the engine down to match it.


Where you might get confused:

  • Changing gear earlier helps acceleration.
  • First gear is for 0-10mph, second for 10-20, etc.

The reality:

Higher gears allow the wheels to go faster in relation to the engine. BUT because the engine is turning more slowly in relation to the wheels, this means that the engine is producing less power and the car will accelerate more slowly.

So if you try to change to the higher gears too early, you’ll just kill your acceleration.

First gear, of course, is the gear that is used to get the car moving away in most cases, but has the lowest top speed.

Top gear (usually 5th, but some cars have 6 gears) gives the widest range of speeds, but the slowest acceleration. In many family cars, the ranges of speeds that are typically best for each gear are:

1st:           0-15mph

2nd:          5-25mph

3rd:           15-40mph

4th:           25mph plus

5th:           40mph plus

Block Gear Changing:

The table shows that there is a big overlap between what’s available to you in each gear. This gives you some flexibility in terms of how quickly you need to accelerate, whether you are going up or down a hill, etc. It also shows that it’s possible to miss out gears when you accelerate, for example, 2nd to 4th or 3rd to 5th. This has quite a few advantages:

1. You are able to match your speed to the conditions earlier, especially in roads with limits of 40mph and over.

2. Better fuel economy because you spend less time accelerating. Acceleration uses more fuel than going at a constant speed because the engine has to work harder.

3. You can spend less time changing gear and more time concentrating on the road.

The only difference between a block change and a normal gear change is that you need to leave the gas pedal alone and the clutch down slightly longer because the gearbox will turn much more slowly when it's in the higher gear.

Changing Down:

The best way to change to a lower gear is to separate the braking from the gear change & choose the right gear for your speed after you finish braking. That way, you spend less time coasting and more time allowing the engine to help the car slow down. The trick to this is to keep your distance from the vehicle in front so that you have more time to read the speedometer and decide which gear you really need.

Remember...

Match your speed to the situation.

Match your gear to the speed!

More driving advice on driving can also be found here:

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