Why Do You Double Clutch a Semi?

The purpose of the double-clutch technique is to aid in matching the rotational speed of the input shaft being driven by the engine to the rotational speed of the gear the driver wishes to select. ... When the speeds are matched, the gear will engage smoothly and no clutch is required.

Is double clutching required for CDL?

Most states will require double clutching when taking the CDL Skills test. You will not have to go through all the gears, but you must be able to select the proper gear for the road condition.

Why do you have to double clutch in a semi truck?

The reason you have to Double Clutch, as opposed to Single Clutch, is that the input shaft speed in the transmission needs to change, so it lines up with the output shaft. When you double clutch, you re-engage the clutch in the middle of the shift, which allows the engine to change the speed of the input shaft.