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How to drive smoothly with an 18-speed truck gearbox

Eaton Fuller transmissions, also called Road Rangers, are manual gearboxes found in trucks. They are range from 9 to 18 gears. We’ve already covered how to change gear using an 18-speed gearbox. This article explains how to get the best performance out of the gearbox and ensure you don’t damage it.

You can do a Roadranger course to give you more details.

Shift pattern for an 18-speed gearbox

How to set off

Your truck is stationary and you need to get moving. The parking brake should be on and the gearstick in neutral. To get it into gear, you’ll push the clutch the whole way down to activate the clutch brake – this stops the rotation of the front gearbox so that it can mesh the gears. This is different to when you are shifting, as you’ll only push the clutch down around halfway to change gears.

If you don’t have a clutch brake, you’ll have a countershaft brake which is a button on the side of the gearstick. You’ll still need to push the clutch the whole way in.

With both the clutch brake and countershaft brake, you only use these when stationary, not when moving, otherwise you’ll get jerky shifts.

The gear to choose is one where you don’t have to use the throttle to move away. As you bring the clutch up, the truck should start to move forwards under the torque of the engine idling, then apply the throttle. If you have to feather the clutch and use the throttle, you should change to a lower gear.

Do you have to use the clutch when changing gears?

Some drivers will ‘float’ gears; this means not using the clutch to change and simply matching the revs. Eaton itself recommends this technique is not used and that drivers should always use the clutch to change gear.

If you do float gears and you’re not getting your technique right, you’ll put more wear and tear on the gearbox.

How to reverse with an 18-speed gearbox

An 18-speed gearbox has four reverse speeds: hi and lo range, plus the splitter. When reversing with a trailer, you’ll most likely use the lower speeds, but if you have no trailer and a long way to reverse, the higher speeds are useful.

Never change range (i.e. lo to hi or hi to lo) while in reverse as it can break the pins on the synchroniser hub.

How to smoothly change gears

Always double clutch: clutch to neutral, clutch to gear. If you’re experiencing a jerky shift, your most likely pushing the clutch down too far and activating the clutch brake. One way around this is to move your seat slightly further back, but make sure this doesn’t mean your steering position is uncomfortable.

If you’re finding it difficult to get it in gear and you’re sure you are using the clutch correctly, you might not have the gearstick in the right position in the gate. The gearstick is sprung so that it sits precisely between gears 1 and 2, so pushing it directly up should access gear 1 and pulling directly back should access gear 2. The gate for gear positions 3 and 4 are over to the right, then up or down. The gate for gear positions reverse and lo are over to the left, then up or down. While stationary, move the gearstick left and right to feel the extent of movement. With the engine off, you can practice finding the gate positions – this is always a good thing to do when you jump in a different truck.

To change between ranges, preselect hi or lo before you move the gearstick, never when you’re in neutral. The range is changed automatically as you go through the neutral position.

Don’t move the gear shift to lo position when you are in high range. The lo gear (not to be confused with lo range) is a crawler gear designed to get you moving when you have a heavy load or are on a steep incline.

When changing down a gear, drop the revs to below 1000rpm before changing so that there’s less risk of over-revving the engine. On a steep downhill, you might want to come down to 800rpm to get that extra engine braking because when you change gear, you’ll lose the engine braking momentarily.

Don’t rest your foot on the clutch or ride the clutch. Even a small amount of pressure on the clutch pedal can start to separate the clutch plates, causing them to slip which will cause wear and tear.

Finally, don’t shock load the transmission. This can happen if you hit a loading dock (the engine’s torque will want to keep turning the wheels, but the dock will stop the truck from moving backwards). It can also happen if you wheelspin but then the wheels grip suddenly.

Which gears should you use?

Most of the time you’ll start in 3 or 4 unless you are heavily loaded, driving off-road or on a steep incline. Gears 1-4 are slow gears which don’t give you that much speed. If you are pulling very heavy loads, then you might use gears 1-4 with overdrive (using the splitter), too. However, you’ll use gears 5-8 much more frequently. Once you’re rolling gear 5 will be your go-to gear for intersections and slow-speed work (again, unless you’re heavily loaded); it’s also the first gear where you start to pick up speed.

Darren has owned several companies in the automotive, advertising and education industries. He has run driving theory educational websites since 2010.

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