Jan 20, 2021



Most of our readers are already seasoned techs or shop owners who know their way around heavy-duty diesel equipment. If this is you, then we’ll be upfront: this article is probably entry-level. But every now and then we like to explore elements of preventive maintenance, and today, we’re going to look at that most oddly named of parts: the zerk.

What Is a Zerk?

Simply put, a zerk is a fitting that lets you inject grease lubricant into wear points on cars or trucks. This allows smooth, steady movement and better overall handling. A zerk “allows you to put grease in a specific area instead of all over,” says Russ Schwartzman, Fullbay’s Professional Services Manager in Onboarding. “Think of it as a one-way valve … holding the grease in.”

OK, but what about that name?

For the curious, the zerk is not named after a hostile alien species (sorry, Starcraft fans). The truth of the matter is that Oscar U. Zerk successfully patented the zerk fitting way back in 1929.

Where Do Zerks Live?

Since we focus on heavy-duty equipment here at Fullbay, we’ll stick to where zerks are located on trucks. You can find them in the following places:

  • Wheel ends
  • Hinge or pivot joints (hoods, covers, 5th wheel mounts)
  • 5th wheel plate and lock
  • Steering linkages
  • Drivelines
  • Clutch linkages
  • Pedals and levers

Tools for Zerk Lubing

There are a few essential tools you’ll need for zerk lubing. While some vehicles might require more specialized tools or techniques, below are the tools you’ll need to get started.

  • Standard grease gun: If you don’t already have a standard grease gun in your shop, it’s time to get one. You will need this handy tool sooner or later. It holds an entire tube of grease. What’s more, it creates the right angle to help you press grease into tough-to-deal-with fittings. Some have swivel heads and long hoses to make zerk lubing easier in tight spots.
  • Fitting rejuvenator: If a zerk hasn’t been greased in a while, the bearing could become stuck in the opening. When zerks seize up in this way, rejuvenators may be your best bet short of replacing them. They are easy to use: fill one with grease, place it over the zerk, and strike it with a hammer. The force of the blow typically jars the bearing loose.
  • Extra zerks: Lubing zerks can occasionally end up damaging them. When this happens, or if a rejuvenator can’t solve the problem, just replace it. Get a pack of assorted sizes. Then you’ll have them when you need them!

Lubing a Zerk: Some Safety Tips

  • Ensure the fitting is clean before attaching the grease gun; you don’t want to get dirt into the fitting.
  • Pump in grease until increased resistance is felt or heard, then stop.
  • Troy from TDI Fleet Services wants to stress that you should have a lubrication diagram for reference when you’re servicing equipment you aren’t familiar with. These diagrams, he says, “Show all the different lubrication points on the vehicle or equipment and the desired lubricant type.”

The Fifth Wheel

Semis have a particularly critical lube point: the fifth wheel. This is not the friend you bring along on a double date, and it’s not actually a wheel. It’s a wear plate that connects your trailer to your tractor. In other words, you really want this mechanism to function properly.

When it comes to lubing the fifth wheel, Troy cautions us to never use our hands, as wear plates can have sharp edges that can do a number on your skin. Put on a pair of gloves and get to work: “A good scraping with a flat scraper or putty knife will usually remove surface contaminants sufficiently to allow a new layer of grease to be applied.”

Keeping Up With PM Work

We hope you’ve enjoyed this foray into zerk history and just how critical proper lubrication is to keeping a heavy-duty truck on the road. And we’ve got good news: not only can you use Fullbay to track zerk lubrication as part of your necessary preventive maintenance, you can also use our FleetCross by MOTOR integration to access the kind of helpful diagrams Troy mentioned above.

Want to give us a try? Head for our free demo!


Suz Baldwin