Special Greases For Special Spots
There are a couple of places on the truck that may benefit from a different type of grease than that used for the rest of the chassis, including trailer wheel bearings and fifth wheel plates.
Trailer Hubs: Lubrication for trailer hubs has been moving from the traditional oil bath to semi-fluid greases, and even toward regular-thickness greases.
"At the end of the day when the vehicle shuts down, grease properties help the lubricant stay up in the bearing housing, whereas the gear oils that are commonly used have a tendency to drain back down in the hub," explains John Geyer, industrial marketing specialist for Chevron Global Lubricants. An axle that is warm from shutdown can react with colder ambient temperatures and form some moisture buildup in the hub, resulting in oxidation and corrosion on bearing surfaces where the film layer of lubricating oil may be very thin or non-existent.
However, you can't automatically use the same NLGI No. 2 grease you use for the rest of the chassis. Not all No. 2 grade greases are appropriate to use in a trailer bearing. You still need a grease that will flow easily around the housing and get up into the bearings. That's why semi-fluid greases have become popular. "These greases will soften slightly when the vehicle is running down the road, but some are designed to slightly stiffen back up at the end of the day, thus helping the lubricant to stay up in the housing," Geyer says.
Some fleets are using a No. 2 grade grease in the trailer bearings, says Stede Granger, OEM technical manager for Shell Lubricants. Benefits include the possibility that the hub will run cooler, and that if there are seal issues, it doesn't ooze out of the bearings as fast as an oil or semi-fluid grease.
But it still needs to be the right kind for this application. "Of course the base oil should be right, not too heavy," Granger says. "Some of our fleets have had very good success using No. 2 grease with an ISO viscosity grade 220 base oil. The typical semi-fluid greases being used have an ISO VG 460 base oil in them." Bearing maker Timken recommends using NLGI No. 1 or No. 2 greases when lubricating their trailer bearings, he notes.
If you do want to use grease in your trailer hubs, Geyer cautions against over-greasing. "With a wet lube, you can visually inspect the oil level through the inspection port. After some run time, with wheel hub greases you won't see them as easily as when gear oils are used. Many times [technicians] will want to put more grease in there when, in fact, the initial fill was sufficient."
While you can use regular chassis grease on the plate of your fifth wheel, several companies offer greases specially designed for this purpose.
Shell, for example, recently introduced a Shell Retinax Fifth Wheel Grease packaged in single-use 8-ounce tubes. These tubes look sort of like a toothpaste tube, with a special flat end for distributing the grease across the fifth wheel plate.
"We've had fleets test it and it's lasted 10, 20 times longer than the typical grease out there," says Shell's Granger. It uses a very heavy base oil and a calcium thickener, so it's very waterproof, he says. It also has a high percentage of solid particles, which become embedded in the nooks and crannies of the fifth wheel and the trailer plate, helping to keep them sliding even after the oil portion of the grease no longer remains.
