Many commercial vehicle drivers wonder if the age-old practice of double clutching is still necessary. First, let’s establish a definition of double clutching. In a nutshell, it is clutching after switching out of a gear, then shifting to neutral, and then going up or down to the next gear. This usually has not been done in consumer vehicles, but it’s been common for awhile for commercial vehicles, especially larger ones, to use this technique.
It can be a difficult technique to learn, and if you drive a smaller commercial truck, you probably won’t need to learn how to use it. Even drivers of newer, larger commercial trucks largely do not need to use the double clutching technique. It was introduced in the 1920s and is really only applicable to more primitive gearboxes. The rationale for using it is that it keeps the transmission unloaded and more responsive, which is particularly important when operating a big rig.
If you do happen to drive an older and larger truck, then this technique may still be useful to you. Note that it is still a required component of the Commercial Driver’s License test, so you’ll need to know how to do it at least once anyhow. In your older big rig, the biggest reason this is used is because the transmission speed doesn’t match the engine speed. Some drivers have invested in synchromesh boxes, which help to synchronize engine speeds with transmission speeds. Because it does take time to learn and master double clutching, some truck drivers choose to use floating gears instead. This can bypass using the clutch altogether (except for starting and stopping).
There are many techniques that perform the same task that double clutching does, but they all are optimized for various sizes, experience levels, load sizes, truck models, and many other factors. In the end, it is up to the driver to determine whether double clutching is still necessary.
Categorised in: Engine Repair
This post was written by J and M