Worn and Forgotten

Most trouble free = most neglected in medium duty vehicles.

"When thinking about vehicle maintenance, most people think about engine oil and filters, transmission fluids, axle/differential fluids, air filters, coolant levels, brakes, lights and tire pressures. Dealing with the steering and suspension systems, unless there is a problem, seems to go unnoticed," says David Peno, business unit manager in steering technology for ZF Sales and Service, North America, LLC.

Peno says that one of the most important steps maintenance managers can take is just getting the truck into the shop for a visual inspection as part of a scheduled maintenance program.

"One thing to remember is that no leaks in the steering system should exist. Any leak identified needs to be addressed immediately," he says.

From pumps to reservoirs, filters to gears, steering wheel to front axles, Peno says correctly identifying what component should be replaced is a hurdle for many fleets. All too often, the wrong components are exchanged, costing fleets more money in repair, when the solution could have been as simple as checking fluid levels or changing a filter element.

"The steering system is designed to be as maintenance free as possible. There are certain maintenance checks that are requested by the manufacturers that need to be adhered to."

Peno says that if the operator identifies a steering system-related problem, it is most important that the problem is clearly identified. For example, it should be determined when the problem happened, and how long has it been occurring.

"Starting with the simple basics such as proper oil level, type and condition should be utilized. If the oil is contaminated, just changing the fluid and filter does not necessarily resolve the issue. You need to find out why the fluid is contaminated, and if the steering lines, pump or gears are also contaminated. Proper diagnosing is key before taking any corrective action," he says.

Freightliner's take on steering components is a scaled down version of their class eight steering systems. Sean Tabari, project engineer in chassis engineering, says maintenance-free doesn't necessarily mean maintenance free.

"Drag links should be checked for tightness of the end sockets routinely. Plus, they have to be greased every 100,000 miles," he says.

Tabari also says the intermediate shaft (I-shaft) deserves some attention as well.

"The entire I-shaft in our design is also virtually maintenance-free. However, visually checking the I-shaft and the tightness of the U-joints routinely is ideal."

Bob Crepas, product specialist in commercial vehicle service for the Dana Corporation, says the best way to prevent steer axle component wear is to understand correct greasing procedures.

"There are three key areas every maintenance professional needs to know to properly grease: how often to grease; how to grease; and how to select the right grease."

"Knowing how often to grease depends upon the application in which the vehicle is operating," Crepas says. "For instance, a vehicle operating in the southwest, traveling for the most part on the highway, would not be exposed to large amounts of contamination and would not need to be greased as often as a vehicle operating with a majority of its time in an off-road application in Canada.

"It's important that the maintenance professional understands the environment in which the vehicle is running. They may need to grease at greater intervals than recommended, ensuring that the steer axle components do not wear out prematurely."

Second, knowing how to grease is equally important. Crepas says the key here is to always make certain that you apply enough grease to push out the old grease with its contaminants.

"Some people think you can add a small amount of grease and then stop. That's not the case. Keep greasing until you see fresh, clean grease coming from between the shim pack and/or the thrust bearing to beam interface. When greasing a tie rod end, apply the same method; grease until the contamination is pushed out."

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