The 18 speed transmission is strong, versatile and easy to use, once you get the hang of the pattern and if you are experienced with manual transmissions. It’s not the easiest of transmissions if you are just starting to learn to drive a tractor trailer.

Versatility is the best feature of the 18 speed. The driver can always have the right gear to keep the truck engine running at the correct RPM to save fuel and help the truck engine last.

For most truck drivers, the 18 speed transmission has more gears than you’ll ever need to use, unless perhaps you’re pulling trains in the mountains or heavy weight. There’s a gear for all situations the driver might encounter.

Shift-pattern-diagram

Shift pattern for an 18 speed

The 18 speed transmission is laid out in an ‘H’ pattern. The easiest way to become familiar with the 18 speed is to practice shifting in an H pattern.

  • The driver uses second, third, fourth, and fifth, then splits up into high range. Then, shift the H pattern again for sixth, seventh, eighth and ninth gear.
  • After reaching ninth gear, split up to overdrive for the top gear.

There are plenty of other gears in between, as all main gears have a high range and low range, so that the driver can split any of the gears, twice more.

It might sound a bit complicated at first, but it’s really not. The more the driver practices, and the more experience he gains, he may find that at the gear being used, may not be quite the right one for where he wants the RPM’S to be.

In that case, they can be split up or down accordingly, matching the RPM’S to the engine’s sweet spot.

Drivers who like floating gears should like the 18 speed, as 12 of the 18 gears available do not require moving the shifter, as they are split gears.

Shifting tips

  • Shifting properly is kind of like riding a bike. The more you practice, the better you’ll get at it.
  • You can have two trucks, identically spec’ed and they’ll shift differently. Every truck shifts a little differently, they each have their own personality.
  • Just take the time to get to know what your truck likes. Find where the sweet spots are.
  • Shifting should be done slowly and methodically. Feather the clutch and feather the fuel to help slide it into gear.
  • Never try to force a gear. It isn’t necessary. It will slide in virtually on its own if everything is lined up right, the speed and the RPM and the shifter.
  • Relax. It’s not something to be rushed. Practice, practice, practice.

18 speed transmission shift pattern diagram

This is a very simple basic diagram of the shifting pattern of an 18 speed transmission. This is the best way to understand the positioning of all 18 gears.

3 reverse gears — Why anyone would want or need 3 different speeds in reverse is beyond me, but the with 18 speed transmission, there are 3 reverse speeds.

3 LO gears (1,2,3) — There may be times when you’re trying to lift a heavy load from a dead stop, or trying to get a set of loaded B trains going from a dead stop after chaining up on a grade. In this situation, the 3 low forward starting gears of the 18 speed, are just the ticket to a smooth start. It’s easy to get a heavy load rolling without abusing the clutch.

15 forward gears — in 3 H patterns.

For the average driver, many of these gears will never be used, depending on the weight of the load, terrain and several other factors.

Source: www.smart-trucking.com