Into the grease

Grease both the fittings on the fifth wheel and the top plate. Clean the top surface of the plate first, then distribute grease all around.

Your truck’s chassis is a complicated system of moving parts of several different kinds. The chassis requires frequent lubrication. The goal of greasing it is to extend the life of all the components that bear weight or handle torque. An oil or grease of sufficient viscosity will cause the parts to fully separate so there is no metal-to-metal contact, extending their life significantly.

Grease is liquid petroleum or synthetic oil much like what is used in your engine, except that it is mixed with a carrier or “thickener” similar to soap. The purpose of the thickener is to make it easier to keep the grease inside a simple seal, typically made of rubber, that surrounds the greased bearings on a truck.

There are several basic grades of grease and different specialized types for certain special parts of the truck. The items on the chassis that require greasing are parts such as kingpins, steering shaft U-joints and links, spring shackles, slack adjusters, brake camshaft bushings, driveshaft U-joints and others. Chassis grease normally is formulated to meet NLGI (or National Lubricating Grease Institute) grades 1 and 2. Most truck makers recommend NLGI No. 2 multipurpose chassis grease for use in normal weather, with No. 1 being reserved for extreme cold.

Make sure to check the appropriate chart in your owner’s manual for the proper grade of grease to use at each location. For example, the Peterbilt manual recommends CL or multi-purpose chassis grease for use in locations such as the driveshaft splines (where the shaft changes length as the truck goes over bumps), the steering column, steering drag link and knuckles, spring pins and slack adjusters. Driveshaft U-joints should get EP or “extreme pressure” lube. Where wheel bearings are greased, they get WB or special wheel-bearing grease. Brake cam bushings get HT, which stands for high temperature, since they absorb heat from the braking system. Alternator, fan hub, clutch release bearings and water pump bearings get BB or ball-bearing grease. Check the recommendations for your particular truck or tractor and for each component.

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Some grease manufacturers sell specialized grades of synthetic grease, designed to protect better and allow extended greasing intervals in some applications, particularly if you are using a premium chassis grease (synthetic greases are available) or opting for special extended service features.

Joe Gibson, service manager at Truck Enterprises, a Kenworth dealer with eight outlets in Virginia, recommends at least one greasing between oil change intervals – preferably two. The best interval depends on where and how you run; in areas with road salt, hilly terrain and a lot of wet weather (which tends to wash grease out of bearings), more frequent greasing is ideal.

On a typical late-model truck running over the road and getting more than 6 mpg, Gibson’s recommendation would mean greasing every 15,000 miles. But the ideal would be every 10,000 miles so there would be two greasings between 30,000-mile oil change intervals.

The Kenworth manual recommends greasing steering linkage parts and brake camshafts at 10,000-15,000 miles but, with the Extended Service Interval package, the interval increases to 25,000 miles. Consult your owner’s manual.

The fluid level in the transmission and axles should always be checked and, if necessary, refilled when doing a grease job. Manual transmission and drive axle manufacturers today favor the use of synthetic lubes. For example, Eaton/Fuller recommends several 50-weight fully synthetic lubes by specific brand name and specification for their transmissions. Depending upon the exact specification, the change interval may be 240,000 miles or more.

The only reason not to use a synthetic would be that you run where it’s so dusty that the lube needs to be changed frequently just to keep it clean. In this case, observe the need for a special, early change interval, as well as frequent regular changes.

Axles use synthetics, too, and the change interval is considerably longer with synthetics there as well. The change interval may vary with certain options like a pump and filter or with the type of use, so read the fine print. Axle and transmission lubes are very different from one another, so make sure you use the correct axle or transmission lube for the particular component. Axle lubes have special EP anti-wear additives because they use “hypoid” curved gear teeth that slide across one another. But axles run cooler than transmissions. Transmissions get so hot that those axle additives break down and can prove damaging to the internal parts.

To check and fill axle and transmission fluid reservoirs, first clean and then remove the plug from the side of the housing (not the bottom). The fluid level should be right at the bottom of the hole – just reach in and feel it with your finger. Put fresh fluid in until it just reaches the bottom of the hole. This may be easier if you use a syringe with a rubber bulb on top. Then reinstall the plug and snug it up.

Periodic disassembly and greasing of wheel bearings is a requirement of any maintenance program. This means cleaning them, replacing their seals and setting the tension or “end-play” on the bearing when it’s reassembled. This is a complex job best left to an experienced technician unless you’ve done quite a bit of mechanical work. Check your manual for intervals.

Many truck wheel bearings, especially those on the steer axle and trailer, use oil rather than grease. Oil does an excellent job because, being a liquid, it is distributed evenly over the parts of the bearing, typically of a roller type, and it carries heat away. However, because the lube is a liquid, the seals have to be of high quality and properly installed.

Because of the potential for leaks, some wheel bearings are greased or may use a special semi-solid grease that is thicker than oil and thus resists leakage. Greased wheel bearings can only be re-lubricated when disassembled. Gibson prefers oil-lubricated wheel bearings because, once there is a leak, it is “easy to see” when doing a daily walk-around, and you can immediately fix the problem.

Special permanently sealed wheel bearings are available, and these require only a periodic check for leakage and to make sure they have not developed play. Gibson says the LMS hubs of this type that are optional on Kenworths are great because “you never have to worry about them.” Wheel bearings that use oil are refilled as is done with the transmission and rear axle.

The oil used in steer and trailer wheel bearings typically is similar to transmission fluid, and this includes Kenworths, Gibson says. Make sure to check the specifications in your service manual. Most drive-axle wheel bearings are supplied with lube from the axle’s sump. Where they are not supplied directly from the axle sump, they normally use a similar lube and, again, are checked and filled as is done with the transmission.

Gibson recommends refilling the hub with the wheels off the ground. Spin the wheel to distribute the lube inside the bearing as you fill it and pour slowly. Just wipe off, unscrew the plug in the top and fill to the proper level. There is a plastic cover with a line on it to indicate when the bearing is full. Reinstall the plug and tighten until just snug.

You should also check items like the power steering fluid level when lubing the chassis and may want to lube minor parts like the door hinges at the same time.

Doing the job
A typical grease fitting consists of a bearing surrounded by a rubber sealing system and is fed grease through a “zerk” fitting, named after its inventor. The purpose of periodic greasing is to force contaminated grease out of the fitting and replace it with fresh grease that is free of moisture, dirt and wear metals. Frequent greasing preserves wearing parts by removing contamination and ensuring an adequate supply of lube that has not been subjected to heat and mechanical stress.

Greasing involves forcing grease into a bearing through the zerk. Grease guns are capable of producing high pressure because sometimes the old grease has congealed and blocks the flow of new grease into the fitting. The nozzle of the gun has jaws that grab the fitting. Once the gun begins to build pressure, the grease pressure actually gets behind the jaws and helps to hold them tightly closed so the nozzle on the end of the gun will stay connected to the zerk no matter how hard you pump.

Buy a grease gun that holds a large volume of grease and has a long handle that gives you a large mechanical advantage. Manual guns are recommended over air-powered guns because it’s better not to force the grease into the fitting too rapidly. Check your owner’s manual for specific procedures for the different types of bearings. You may need a jack and axle stands to raise the chassis.

  1. The first step in any greasing procedure is to clean the zerk. Road dirt sticks to these fittings because of trace amounts of grease left over. Unless it is removed, the dirt gets pumped right into the bearing, causing unnecessary wear of both the bearing and seals. So wipe each fitting carefully with a clean rag before you connect the grease gun.
  2. Once the fitting is clean, force the nozzle on the front of the gun securely onto the fitting. You’ll feel resistance at first. Then the jaws will grab when they pass over the rounded end of the zerk. You’ll actually feel the nozzle click onto the zerk.
  3. Begin steadily and slowly pumping the handle on the gun until old grease starts to emerge from the fitting and is then followed by fresh grease. The goal is to fill the seals with grease and purge the old, contaminated and broken-down lubricant.
  4. Check in your owner’s manual for specific procedures that will help the grease flow properly around the load-bearing parts. As mentioned, also make sure to use the appropriate grease if different types are required at different fittings. This would mean using separate grease guns or changing the grease cartridge as necessary.

For example, on Volvo VN vehicles, the factory recommends lubricating the front-axle spring pins with the axle hanging freely from the chassis. Only when the weight is removed can the grease get in between the working parts.

To lube the front axle with the wheels off the ground, you’ll need a powerful floor jack and axle stands with more-than-adequate load ratings for the weight of the tractor. Adjust the height of the axle stands so the wheels will be off the ground. This is normally done by pulling out a cotter pin and support pin, lengthening or shortening the height of the stand by grabbing it by the saddle on the top, reinserting the support pin through the holes, then locking it with the cotter pin.

Raise the vehicle, then place the axle stands squarely under the frame rails. Lower the frame and make certain it is secure. Volvo says spring pins should get a lithium-based grease with EP additives with NLGI No. 2 consistency. “Fill both fittings until old grease has been pushed out past the seal on both sides and new grease can be seen flowing,” the manual states. If grease does not flow through, use a pry-bar to lever the spring ends downward to open up the gaps between the internal parts.

On the VN, you should lubricate the steering shaft, drag link and tie rod every four months. The TRW steering gear has a fitting at the sector shaft (the part that connects to the steering linkage that goes to the wheels), while the Sheppard steering gear has such a fitting at both the input shaft that comes down from the steering wheel and the sector shaft that outputs the force to the linkage. A hand grease gun is preferred.

The steering knuckles are right behind (inside) the wheels and rotate when you turn the steering wheel. These have the kingpins inside. When lubricating Meritor and Eaton front axles, have the vehicle raised off the floor, as when lubing the spring pins. When lubricating the steering knuckles on a Volvo front axle, the vehicle should be sitting on the wheels. There are fittings top and bottom, and you should apply grease until all the old grease is forced out past the seal at top and bottom.

Volvo brake cam bushings and slack adjusters need a lithium-based, NLGI No. 2 grease with EP additives. Note that Meritor brake systems have special grease requirements. Securely block the wheels and release the parking brake so the tension will be off the brake camshaft and grease can surround all the parts. Grease the single fitting just until fresh grease appears.
Slack adjusters should be greased until old grease is forced out past the center of the unit (where there are splines, or grooves) and you can only see fresh grease.

When lubricating driveshafts, always make sure the grease comes out of all four seals of the cross at either end. If one of the seals fails to purge of old grease (you can’t see fresh grease), move the driveshaft from side-to-side while continuing to apply pressure with the gun. This increases the clearance and allows the grease to flow in. “New grease flushes abrasive contaminants from each bearing and assures that the bearing is filled properly,” according to the Volvo manual.

For more information:
Truck Enterprises
(800) 296-8782

Peterbilt Motors
(940) 591-4000

Kenworth Truck Co.
(425) 828-5000

Volvo Trucks of North America
(336) 393-2000

(816) 931-9480

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