Worn and Forgotten

Most trouble free = most neglected in medium duty vehicles.

"The axles are bolted to the suspension with U-bolts," Gadowski adds. "It is important for maintenance managers to visually check the clamp group for signs of loosening. Also check the U-bolt torque per vehicle manufacturer's specification. If left unchecked it can lead to other failures and a costly repair bill."

Maintenance recommendations from the original equipment manufacturers (OEM) is the best way for maintenance managers to configure a maintenance schedule for their trucks.

"We use a combination of truck manufacturers' recommendations combined with the manufacturer's recommendations from the mounted equipment we use on our trucks," says Wesley Keller, transportation manager for PPL, an electric and gas utility in Pennsylvania.

"We bring the trucks in on a calendar basis, because some of the components or devices require an inspection every so many days. We tie basic inspections in with that," Keller says.

"Some may say we are crazy for bringing the trucks in every three months instead of by miles, but because of the aerial devices and because the truck is already in the shop, we just inspect everything routinely."

"PM is a way of life for us," Keller says. "We don't really have any issues we can't handle as far as the suspensions are concerned. The springs will arc with fatigue or occasionally break because we utilize the chassis at maximum capacity. We know we load our suspensions, but the breakage isn't premature. We expect that this will happen because of how we are loading them down."

ZF's Wappes wants to remind maintenance managers that some parts are made to wear.

"Tie rod ends, draglink ends and torque rods all have wear take-up built in. Once the wear has exceeded the take-up allowed, the part will develop lash. Lash indicates the end of the part's life, signaling time for replacement," he says.

"If you don't replace them before they wear too much, they could come apart and you could run into major problems," Wappes concludes. "Knowing and understanding this will help prevent major structural problems down the road. Not all parts are meant to last forever."

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