By Paul Abelson
senior technical editor
Preventive maintenance cycles are built around oil changes. Talk about lubrication, and we immediately think oil. There’s plenty written about new oils and oil drain intervals. But oil is just one lubricant we use on trucks. We rarely hear about the improvements made to the other lubricant – grease.
Grease lubricates merely by being there. It is used to lubricate steering kingpins, suspension bushings, trailer kingpins, fifth wheels, universal joints and more. These are separate systems that need clean grease kept in one place.
Commonly, grease is forced into a zerk fitting. Zerk fittings have a ball held in place by a spring. When grease pressure against the spring is strong enough, the spring yields, the ball moves back from the opening and grease flows through the zerk’s hollow center to wherever it is needed.
Elastomer seals around the bearing, kingpin or shaft to hold grease in place and act like one-way check valves, letting used grease escape when displaced by fresh grease. The seals also prevent contamination from entering the grease chamber.
Most shops have central power lubricating systems. They use compressed air or motorized pumps to deliver grease. Do-it-yourselfers often use the hand held, lever-pumped grease guns. When filling guns with bulk grease, be sure there are no air pockets. Air compresses, so the grease may not be delivered properly. The best hand guns use factory-filled cartridges.
Keeping those fittings properly lubed doesn’t require a trip to the garage or a lot of work at home. In fact with the delivery systems available, you can even give it a squirt or two on the fly.
“Often, I’d get to a shop or quick-lube where they might not be able to reach all the fittings. If they forget one or two, this way I’m covered,” said OOIDA member Dave Tennessen.
That’s why Tennessen invested in an on-board automatic chassis lubrication system for his 1994 Peterbilt 379.
When he team-drove with his wife, Peggy, they took two years to spec their truck for maximum uptime and thorough maintenance. This was to be the last truck they’d ever buy, and they wanted it to have everything.
The automatic system from Lincoln Industrial Corp. lubricates every grease point, except the driveline, with a fresh dose of grease every 4-1/2 hours while the truck is in motion. Dave, a specialized heavy hauler, refills the reservoir every 2,500 to 5,000 miles.
“Peggy is the type of woman,” Dave said, “who always looks like a million bucks – no, make that a million and a half. We’ve been married 20 years and she always has her hair and nails done and her makeup on. She delighted in telling people she was on her way to grease her truck. They wouldn’t believe it.”
The Pete now has 725,000 miles and has never had a lubrication-related problem.
“I still have to crawl under the truck to grease the driveline. I do the clutch throw out bearing at the same time,” Dave said.
Two other systems are available in North America: the Grease Jockey from Lubriquip and Vogel Central Lubrication.
Each delivers a small charge of grease to every fitting at the interval you set. You get partial lubrication from every few miles to every few hundred. That continually keeps the grease clean and effective. On-board lubrication brings a grease line to every fitting on your truck except the spinning parts.
No one has yet figured out how to connect with a fitting on a spinning drive shaft. But both Arvin Meritor and Dana/Roadranger have drive shafts with splines and U-joints with low-friction and hardened materials and long life grease so well sealed, they don’t need lubrication for 250,000 to 350,000 miles.
The Tennessens’ trailer, a drop-deck, is hard to get under. Problems arise when people miss grease points, so Dave worked with Trail King to develop a manifold and lines to take grease from just two fittings to all the points on the trailer that need greasing. One at the rear connects to 18 separate lube points. The one at the gooseneck hits six fittings.
To help make do-it-yourself maintenance easier, Lincoln Industrial also makes three rechargeable, portable power grease guns. The 12-volt PowerLuber develops up to 6,000 psi, comparable to a shop system. The 7.2-volt PowerLuber II reaches 5,000 psi, and the 3.6-volt MiniLuber provides 3,500 psi.
A common mistake is to add only until you see grease start to emerge from a seal. Instead, keep it flowing until you see clean grease a full 360 degrees around the part. It actually takes more to replace grease in a fitting than the volume of the fitting itself, because the new grease must displace all the old plus whatever flows out. You can be sure all the grease inside is new only if 100 percent of the grease flowing out is clean. Wipe off any excess so it doesn’t attract grime.
When is the right time?
Is it best to lubricate a chassis in a loaded or unloaded condition? Some claim that by jacking the chassis just enough to take the load off the suspension, you open things up so grease can fill the space more easily. Others claim clean grease will flow where it’s needed when the chassis flexes. My opinion is to jack the truck if you have time and equipment. It can’t hurt.
How often should you grease your chassis? That depends on routes, operating conditions and grease quality. Don’t exceed owners’ manual maximum recommendations. For protecting parts from wear, there is no such thing as “too often.”
Usually, the recommendation for your “wet PM,” or oil drain, is a multiple of the chassis lube interval. With many modern trucks, both may be the same. If you plan to extend oil drain interval, you may have to cut your greasing interval to stay at a multiple.
For example, if oil change and lube are both 20,000 miles but you extend oil to 30,000, you should do a dry PM at 15,000 miles. By adjusting, you’ll stay within lube recommendations and alternate wet and dry PMs. At the other end, I know dump truck operators and others who visit construction sites who grease weekly. One even does it daily.
If you want to and can extend oil drain intervals significantly (some operators go 70,000 miles or more using bypass filtration), consider an on-board lubrication unit. You just need to refill the reservoirs of these compact devices on a regular basis.
When you stop and think about it, greasing vehicles has come a long way from the days when rendered beef and bear fat were spread on wooden spindles, held in by leather flaps, so wood-spoke iron-rim wheels could turn freely.
Paul Abelson may be reached at firstname.lastname@example.org.