There’s A Reason Why Heavy-Duty Trucks Come With A Power Divider Switch

A power divider switch is something that a semi truck with a tandem drive axle setup, also called a tractor trailer, can have. If a truck has one, it can be used to control which of the truck’s drive axles receives power from the engine. A power divider switch is also known as an inter-axle differential, and when switched off lets the two drive axles rotate separately from each other under normal conditions. This helps them corner better while minimizing wear on the tires and the axles themselves. 

The power divider switch is typically used when traction is lost by one of the truck’s drive axles, which will then send all of the power to the axle that has no traction, causing it to spin. It’s usually located on the panel that houses the accessory switches and may have a guard to prevent it from being accidentally engaged. The power divider switch causes the differentials in both drive axles to be locked together, letting them both turn at the same speed, regardless of whether they have traction or not. 

The power divider switch should be used in slippery conditions like those encountered off-road. It can help to reduce wheelspin on uphill sections and can also reduce brake lockup on downhill sections. Another situation that might require the power divider switch is a steep driveway, when one or more drive wheels could freewheel because they’re not solidly on the ground due to the angle of the driveway. 

Some of the largest semi trucks in the world will usually have a power divider/inter-axle differential switch on their drive axles. When the switch is activated, an indicator light will illuminate in either the switch itself or the instrument cluster. It is extremely important that the driver NOT engage the power divider switch if any of its drive wheels are spinning, if the truck is on a steep downward grade, if traction is limited, or if the truck is going faster than 25 mph (40 km/h). 

Ideally, the truck should be stopped before engaging the switch, to prevent damage to the rear axle. The best approach is to activate the power divider switch before low-traction conditions or steep downhill roads are encountered. Power divider switches are typically found on trucks equipped with air brakes, and they can be found on trucks with both manual or automatic transmissions.

Keep in mind that a power divider switch is completely different from a differential lock. While the power divider switch locks the two drive axles together, a differential lock locks together the wheels on a single axle. Both are used to improve a truck’s traction, but in slightly different ways. This has a lot to do with why most semi-trucks are rear-wheel drive. The power divider switch on a semi truck is a key piece of safety gear that will help the vehicle handle low-traction and slippery conditions in a safer manner.