Advice: Jost Air Release Fifth Wheel Operation

So slow was the uptake that Jost Australia’s Bob Martin told trucksales.com.au that he’d had a brand new air release fifth wheel sitting on the shelf for over two years and couldn’t give it away.

But recently things have changed. “Today, the demand for our Jost Air-Release fifth wheels is so high that we are air freighting them in, just to keep up with demand,” Bob said.

So why the seemingly instant turnaround? “It’s mostly driven by the multi-national fleets that are specifying the air-release fifth wheel,” Bob explained.

“This new demand is attributed in part by the change in trailer designs where we are seeing more and more aerodynamic fairings installed making it harder for drivers to reach in and pull the manual handle to release the fifth wheel mechanism and partly to reduce OH&S risks associated with uncoupling trailers.”

The air-release system is fitted to the standard Jost JSK37 fifth wheel, and uses an air ram under the top plate to release the jaw mechanism when a switch inside the cabin is activated.

However, before you ask, the air-release switch is only active when the park brakes are applied. For added safety the switch is typically covered with a missile style cover, meaning there are two distinct actions required before the jaws will release.

Firstly, the missile cover needs to be raised then the switch activated. As an added feature, there is pull handle so the fifth wheel jaw can be released manually if required.

In most cases there is a light or series of lights on the dash to indicate to the driver the system is active and which stage of release the fifth wheel is in.

To couple a trailer to a vehicle fitted with a Jost air-release fifth wheel, follow your company’s coupling procedure, or review our article on coupling and uncoupling.

Where the procedure for a manual lever style fifth wheel says to inspect the fifth wheel is in the open position, if you notice that the jaw is in the closed position, you need to ensure the vehicle’s park brake is applied and activate the air-release switch in the cabin to open the jaw. Then couple the trailer as per the remainder of the procedure.

Again, follow your company procedure on how to uncouple a semi-trailer or review our article on coupling and uncoupling.

You still need to get out of the truck to disconnect the air and electrical leads then wind down the landing gear. Now where the traditional manual style fifth wheel procedure states to pull the lever, replace this step by ensuring the park brake is applied and then raise the missile switch cover and activate the switch to release the jaws.

Depending on the brand of truck, a display may illuminate in the dash to indicate the action. Once the jaw is in the open position pull your vehicle forward as you normally would in the uncoupling procedure.

Click here for more information on the air-release fifth wheels.