10 steps to trouble-free axles and suspensions

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Before a new truck is put into service, it’s important to measure the torque on fasteners ranging from frame attachments to U-bolts and shocks, suggests Brian Strach, a service manager with Hendrickson.

“Take a calibrated torque wrench and verify they’re tight. If you find them loose, they came from the factory loose … If six months down the road you have an issue [and you didn’t check the torque on delivery], you’re going to get into a finger-pointing game.”

Equally, regular inspections need to continue once the equipment is in service.


As surprising as it may sound, many fleets have failed to determine the wheel end systems that they’re using on specific units, says Al Anderson of ConMet.

“If you don’t know what’s behind the hubcap, you don’t know what maintenance can be performed or should be performed.”


If your mechanics are trying to check end play when wheels are still sitting on the ground, the wheel ends aren’t getting the attention that they need. The only way to determine the measurement is to unload the suspension system, supporting the truck by its frame. (It is a practice that will also offer a clear look at every suspension-related component.)


The end play on conventional bearing packages should be checked every year, while the recommended maintenance schedules for pre-adjusted packages will vary, adds Al Anderson of ConMet.

“The only correct way to measure wheel bearing end play is with a dial indicator, with the wheels, tires and brake drum off,” he says. “Conventional bearing endplay will fall between .001 and .005 inches, and the bearing should be repaired or adjusted at any point beyond that. With unitized wheel ends exceeding .003 inches, the spindle nuts should be re-torqued … but beyond .005, the wheel end should be replaced as a complete unit.”


Wheel ends with leaking seals can be the bane of a maintenance manager’s existence. At worst, the related bearings may run dry, but the leaking fluids can also gum up ABS tone rings.

“Leaks can occur in a number of places,” Anderson adds, referring to the need to watch over areas including the hub cap gasket, around the fill cap, and the inboard side of the wheels.


Even seemingly simple mechanical springs deserve regular attention.

“When a truck has been running for a while [on mechanical springs], you’re going to look for shifting in the spring leaves, or broken spring clips,” Strach says, referring to the general inspection process.

And any repairs should involve all related hardware.

“People will fix a spring, but they won’t look at the mating parts that go around it. If those are worn, those have to be changed,” he says, noting how loose hardware can lead to a break in the middle of a spring.

Meanwhile, while you may expect to see occasional streaks of orange rust weeping from between the springs, there is a way to address the noise associated with the rust. An application of grease will make all the difference in the world.


A well-placed application of grease can solve a number of woes, but maintenance crews should also be careful to ensure that they’re using compatible formulas, notes Matt Sivik of Lubrizol, which creates the additives at the heart of many lubricants.

The most common grease is NLGI 2, while softer greases are used in automatic greasing equipment. (When reading the National Lubricating Grease Institute ratings – identified by the acronym NLGI — a “000” is soft, while a “6” is hard.) The most common offerings are lithium and lithium-complex formulas, while the latter have a higher resistance to heat.

An incompatible mixture may not stay in place.

The choice of grease isn’t the only consideration, either.

“Clean the part before re-greasing, or in the case of grease fittings, apply grease until only fresh grease is coming out of the purge location,” Sivik adds.

If your fleet power washes its equipment, it’s also important to note that the lubrication intervals may need to be shortened.


Meanwhile, maintenance teams shouldn’t be, er, shocked if they discover a shock coated in a mist of oil.

Some fluid will be released during normal operation, Strach says. “But it should be a fine spray. It’s when you have [the fluid] running down and streaming, then it’s leaking and should be changed.”

Inspections also need to involve more than pushing or pulling at the shock itself.

The best approach is to use a “heat test,” which involves running a truck on a rough road for about 10 minutes. (A highway with a few potholes isn’t rough enough. Put the equipment through its paces.) Once stopped, a technician or driver should touch the frame to determine the ambient temperature, and then tap the body of the shock to check its temperature.

“If it’s warmer than the frame, it’s working,” he says.


In addition to checking ride heights, fleets using air ride suspensions should also look for any air lines or cords that come in contact with the air springs, Strach says. That contact could lead to ruptures further down the road.

Related clamp groups also deserve special attention.

“These bolts are going to get corroded, and putting a torque wrench to it, you’re not going to get a true torque reading,” Strach says, referring to the need to watch for signs of rubbing around frame hangers, spring pins and shackle assemblies. “And if problems are found, make sure you look at the mating parts.”


If you’re looking to buy used equipment, also take the time to check the axles for any signs of repair.

“No repair welding or straightening of the axle is allowed,” warns Norm Austin of ArvinMeritor.

They may be simple steps, but they will all play a role in extending the life of your equipment.

John G. Smith is a technical correspondent who provides coverage of equipment-related issues. As former editor of Truck news and Truck West, he shows a passion and deep understanding of industry issues.

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