This guide is meant for those who are new to shifting on 13-speed and 18-speed transmissions.
Most of the basics will be explained to come to a better understanding of the similarities, the differences, and the general layout of the most common 13spd and 18spd transmissions in use.

For now this guide is pretty much bone stock, but perhaps some time down the road I'll be adding some photos or maybe a video or two for more detailed information.

Generally speaking, there are 5 low range gears (basement) and 4 high range gears.
Without a splitter function, this would be a standard 9spd transmission (also known as 8+1).
By using a splitter, this pattern can be turned into either a 13spd or 18spd layout.

The general positions pattern looks like this:


In this pattern:
R = reverse
L = low (crawler)
1/2/3/4 = regular gear positions

With this basic layout, as by having a range selector and a splitter function available, we can now create a basic 13spd and a basic 18spd pattern with this.

The most common setup of a 13 speeds transmission typically has 4+1 gears in the low range selection, and 4 in the upper range. By using the splitter function in the high range, this will give us an additional 4 gears in the upper range, bringing us to a total of 5 + 8 = 13 gears.

The layout would look as follows, starting with the low range.

Similar to a regular car, these gears are shifted in what's known as the H-pattern (based on the positions of gears 1 through 4). The 5th gear in the low range is the L gear, also known as low gear or crawler gear. This is typically used for starting a roll on a considerably heavy load or special transports just to get moving. Since the gear ratio is extremely high, even a moderately powered or even a low powered vehicle would normally have no problem to get a consierable weight moving, even though at a very slow pace. Hence the name, "crawler" gear. Once the whole bulk is at a move though, the regular gears will have no problem to keep up the speed and gradually increase it. On a regular cargo weight however, the L gear is usually skipped and driving starts in the 1st gear position.

Once the vehicle is moving and 4th gear is at its peak performence, we are ready to shift to 5th gear. To get there, we will be using the high range shifting pattern:
[NOTE:] these positions are identical to the positions of 1st to 4th gear in the low range selection.

To get to 5th gear, we will need to use the range selector to switch from the low range of gears to the high range. This is done by going through the following steps, without rushing:
- after 4th gear, use the range selector to pre-select the high range of the transmission
- after high range has been pre-selected, engage the clutch, shift to neutral position and release the clutch. this will allow the transmission to actually switch between the low and high ranges.
- after the switch has been completed, engage the clutch again, rev the engine a bit if needed, to stay in the engine's rpm powerband, and shift to the 1st gear position again, this time in the high range selection.
- release the clutch once the gear lever is in place and continue driving.

The vehicle is now in 5L (5-low) gear, which sits at the same location in our layout as the 1st gear in low range. Now, after picking up some more speed, let's go from 5L to 5H (5-high). For this, we need to do the following:
- use the splitter function to split the 5th gear
- engage the clutch, shift to neutral. this will allow the transmission to make the split happen.
- once split is done, engage clutch again and shift back into 5th gear. We are now in 5H (5-high).

[note:] on some transmissions this move is done by just engage the splitter, releasing the throttle, let the split take place and engaging the throttle again once done. On most transmissions this will work, although it might put some unncessary stress and wear on the clutch itself. However, when running relatively old non-synchronized transmissions it is highly recommended to use the neutral step inbetween the splits to avoid gear mismatching (the typical metal grinding noise).

When we're done with 5-high, the next gear waiting for us is 6L. So let's get to it:
- engage the clutch, disengage the splitter, shift gear level to neutral
- wait a moment for the split to take place, a tiny dab of gas to keep the engine rpm up
- engage the clutch, shift to 6th gear posion.

And we're now in 6L (6-low) gear. And all that's needed to eventually reach 8H, continue this process a few more times, going through 6H, 7L, 7H, 8L and eventually reaching 8H.

Congratulations! This completes the basic idea of running a 13 speeds transmission.

Let's move on to the 18 speeds then, shall we?

For an 18-speeds transmission, the general layout is very similar to that of a 13-speeds transmission. However, there are a few notable differences. Firstly, let's take a closer look at the low range of an 18-speeds:

NOTE: On some transmission the LL/L might be named CL/C or C/CH instead, for crawler-low and crawler, or crawler and crawler-high respectively.

One of the key differences is the extra number of gears in the low range. This is due to the splitter being used on all of the available gear positions. This effectively gives us 10 gears in the lower range instead of the 5 we had in the 13-speeds layout.

However, the method of shifting through these gears is identical to shifting the high range of a 13-speeds, except that this method now works on all of the gears in the lower range also.

So this gives us 2 reverse gears, 2 crawlers, and 8 low range gears.



The same shifting method can be applied to the high range selection:

Note that there is now another 2 reverse gears in the high range of the transmission. However, as a safety mechanism, these gears can never be selected while the vehicle is in a forward rolling motion, even at crawling speed. The vehicle has to be stopped completely before this safety will be disabled by the transmission itself.

Lastly, there are transmission layouts that have a somewhat different setup in the high range selections. However, the difference is only such, that the 7th and 8th gears sit in alternate positions compared to the standard high range layout:


So instead of shifting the high range like a regular H-pattern, this pattern is shifted from 5th (above neutral), to 6th (below neutral), to 7th (lower right), and to 8th (top right). The end effect is still the same though, and so is the effective number of gears available.

The above example was taken out of a custom 13-speeds transmission by order of a client, however this layout seems to become more common these days.

Also, as a side note, the same applies for the 18-speeds version, where 7th and 8th have swapped positions. The additional reverse gears will still be in the top left of the high range.

I hope this information was of some use to you, and hopefully improve your understanding of the various available layouts. If you have any questions concerning this topic, feel free to leave a comment or leave me a message through Steam and I'll see what I can do to answer them.

Happy trucking and drive safe!