How do you drive an 18-speed Roadranger truck gearbox?

Many American and some Asian prime movers and heavy rigid (HR) trucks have a gearbox from Eaton called the Fuller Roadranger (or Road Ranger). Common formats are 9, 13, 15 and 18 gears. These extra ratios give you much more control with heavy loads, on rough terrain and on steep hills.

Driving a Roadranger, though, isn’t the simplest thing to learn (you can do this online Roadranger training course if you really want to be a professional driver). In this article we’re going to explain the basic theory and some tips here that will make your Roadranger experience smooth when you get to drive one.

There are three things to know about how the gearbox works:

1. It functions like a regular manual gearbox in a car, in that it’s an H-pattern
2. There are two switches on the gear stick to change the range (lo and hi) and the splitter. This is what gives you the additional gears
3. You have to match the revs, the road speed and the gear

The pattern is like a regular car manual gearbox, but the black and grey switches you see in the image above on the right-hand side determine which gear ratio you’re in.

Let’s ignore the two gears on the left-side of the gate for the moment and concentrate on the 1, 2, 3, 4 gears you can see in the centre and right.

When the gearstick is at rest, it will sit between one and two. To get it into gear one, make sure the black switch is down and the grey switch is back, then push the gearstick up into gear one. To move to gear two, pull the gearstick back into position two, and so on.

How do you change gears?

The most important part of changing gears is matching the revs to the road speed and picking the correct gear. This is much easier on an upshift than a downshift.

Some drivers don’t use the clutch – this is called ‘floating the gears’, but Eaton does not recommend this as it can wear the gearbox out prematurely.

The recommended process is double clutching. This means you press the clutch twice in the process, once to put the gear lever in neutral and once to put it back in gear. So, when changing gear up within the same range (e.g. 1 to 2, 2 to 3, 3 to 4), this is the process

1. Release the throttle/accelerator
2. Push the clutch in about halfway so you feel the friction point
3. Move the gear lever to neutral
4. Bring the clutch up
5. Push the clutch in about halfway to the friction point
6. Move the gear lever to the next gear as the revs fall away (the gear lever should just notch into gear)
7. Bring the clutch up
8. Get back on the throttle

This can be described as clutch-neutral, clutch-gear.

The downshift introduces one extra step

1. Release the throttle/accelerator
2. Push the clutch in about halfway so you feel the friction point
3. Move the gear lever to neutral
4. Bring the clutch up
5. Push the throttle to give a few revs
6. Push the clutch in about halfway to the friction point
7. Move the gear lever to the next gear
8. Bring the clutch up
9. Get back on the throttle

Remember that you are matching the revs, so if you’re coming down a gear and you were doing 1000rpm, your revs will match somewhere between 300-500 above that, depending on your gear ratios.

The splitter

The grey switch acts like an overdrive for each gear – in fact, it’s sometimes called overdrive when it’s in the forward position and direct when it’s in the rearward position. On the diagram its represented by H and L in each position – confusion for drivers given that Eaton also has Hi and Lo range, and a Lo gear.

When you’re in gear 1, if you push the split forward, you’ll get, what is effectively, gear 1.5. This is around half way between gear 1 and 2 in terms of revs.

To change gear using the splitter, you don’t have to move the gearstick. You simply pre-select it, then when you want to change, lift off the throttle a little and you’ll hear it change, then get back on the throttle – very easy.

With the splitter, you end up having 8 gears in that H pattern. 1 direct, 1 overdrive, 2 direct, 2 overdrive and so on.

You probably won’t use the splitter very much unless you’re either driving off-road or carrying heavy loads on a steep grade.

Hi and lo range

The black switch on the front of the gearstick moves you between ranges. If you flip the switch up, gear position 1 now becomes gear 5. Gear 2 becomes gear 6 and so on. As with lo range, you can also use the splitter. So, you get gears 5 direct, 5 overdrive, 6 direct, 6 overdrive and so on, right up to 8 overdrive which is your top gear.

To change between ranges, you preselect the switch and as soon as the gear lever passes through neutral, it will change.

For example, if you want to go from gear 4 overdrive to gear 5 (a combination shift), here’s the process:

1. Move the splitter to the rearward position
2. Move the range selector to the upper position
3. Come off the throttle
4. Push the clutch down
5. Put the gearbox in neutral
6. Bring the clutch up and then down again
7. Put the gearbox in fifth gear
8. Bring the clutch up
9. Press the accelerator

Now we’ve established that you have two sets of 8 gear ratios, which means 16 gears. Where do we get the other two from?

Lo gear

On the bottom left of the shifter you’ll see a Lo gear – don’t confuse this with lo range. You can split the Lo gear, but it only works in lo range, not hi range, so that gives you an extra couple of gears for a total of 18.

Reverse

Finally, on the top left you have reverse. Reverse works in both high and lo range (although you should not switch between them while moving), and you can use the splitter, too. That gives you four reverse gears.

Block shifting

Block shifting is where you miss gears. It reduces wear and tear on your gearbox, so it’s advisable when you’re on flat or downhill gradients or you are empty of lightly loaded.

For example, rather than going from 5 to 6, you might go from 5 straight to 7, missing out 6. The same can be done on downshifts. You’re changing gear to help lose speed along with the engine braking, but ultimately you mostly only need to get down to gear 5 for most low-speed intersections, so you could go from 8 to 7 to 5, missing 6 on the way.

Driving with a Road Ranger

Learning the smoothest gear change technique will give you better fuel economy in your truck, less wear and tear on your transmission and will reduce fatigue for you while driving. But, you can’t just learn by reading this article, you need to apply your new knowledge in the cab.