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Excessive vibration can kill your truck

CALGARY, Alta. - Owner/operator Stuart Mitchell says his logging truck has a form of cancer that is reducing its life expectancy and causing him a healthy dent in the pocketbook as well.The truck is s...


CALGARY, Alta. – Owner/operator Stuart Mitchell says his logging truck has a form of cancer that is reducing its life expectancy and causing him a healthy dent in the pocketbook as well.

The truck is suffering from a nasty vibration that he has spent many months chasing down and still hasn’t found a permanent fix for.

Now, he tells anyone who will listen to beware of abnormal vibrations, which he says will eventually shake a truck apart.

“All trucks have harmonic vibration,” says Mitchell.

However he realized his truck was experiencing much more vibration than your typical logging truck.

“It vibrated the locking hubs right off (the wheels),” says Mitchell.

“It will really attack the weakest link.”

Mitchell first noticed the excessive vibration on his rig shortly after taking delivery of the truck.

Since then, he has experienced a lot of downtime while trying to chase down the cause.

“Once you have a vibration, good luck in having someone accept fault,” he says.

He’s been caught in the middle of a seesaw battle between the truck dealership and the engine manufacturer.

Meanwhile, he has had to keep it on the road by applying a temporary solution – soft motor mounts, which reduce the vibration to a tolerable level.

“If you keep soft motor mounts in the truck, it stops this one,” says Mitchell.

“But it’s a logging truck so it tears the soft motor mounts out right away so that vibration is leading to a lot of costly expenses.”

Mitchell is not the only O/O coping with vibration problems.

It’s actually quite a common problem, and as Mitchell attends to, it can be very difficult to trace.

Charlie Allen of ZF Meritor, says torsional vibration can often be controlled by installing a long-travel dampened (LTD) clutch.

“The way it helps the torsionals is that it has softer rated springs and it allows for more travel and more displacement of the springs,” says Allen.

As of Jan. 1, 1997, the company began recommending an LTD clutch be used on all new trucks.

That’s largely because the company’s test results indicate even the best configurations on the road cause a fair amount of torsional vibration.

“In most cases, you probably have to spec’ it,” says Allen.

“The suggestion I would make to someone is that they ask to make sure there is an LTD clutch included and if there isn’t, they need to ask for one.”

When it comes time to replace a clutch, Allen says it’s even more important to use a similar clutch.

“If the truck was equipped with an LTD clutch, you need to replace it with a like clutch,” he warns.

“I think you’re going to be fooling yourself in the long run if you spec a non-LTD clutch in place of an LTD clutch. You will break things.”

While not all torsional vibration can be traced back to the clutch, Allen says it plays a big part in controlling it.

“What generates the torsions is the engine, but it is the clutch that helps control it,” says Allen.

If you think excessive torsional vibration may be a problem with your truck, there are some telltale signs to look for.

When carrying out regular maintenance tasks, look for damage to gearing, broken synchronizer pins and damaged driveline universal joints and universal joint slip sections.

If your truck is showing some of the symptoms of torsional vibration, it may be time to spec’ an LTD clutch.

“If you have a non-LTD clutch in most cases you can interchange an LTD clutch with it, assuming the flywheel openings are big enough for the damper,” says Allen. “That’s probably a good upgrade to make.”

However, he does warn truck owners to shy away from some of the no-name clutches on the market.

“There are some aftermarket parts where you’ve got some modified springs where they fill them with rubber and they don’t perform as well,” says Allen. “There’s no way anyone can be sure of their performance.”

While an LTD clutch may not solve all of Mitchell’s woes, he does have some words of wisdom for O/Os.

“Just leave it on the lot,” he says. “Don’t buy a truck with vibration because it just eats away at your truck.”


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