Ask The Mechanic

Grease Job

Image by Steve Thompson

Q: It’s time around our place to repack the dreaded wheel bearings on all of our utility trailers. We put it off, and we put it off again, but now we must “bite the grease” and just take time to do it. The big question I can’t get answered at the coffee shop is what exactly is the best way to repack the bearings? Can you give me a few tips before I get grease all over me?

A: We all feel your grease on this job. Because bearings are key players on almost everything around the farm or ranch, it’s important they get a little respect, because a hot bearing can cause great damage to machines and set fires. As shown in the photo above, sometimes bearings can be abused. The two bearings in the photo are the exact same bearing from a piece of hay equipment. Bearings come in all shapes and styles, wooden to sealed to cone bearings, like those on trailer axles, and many more. Here are a few tips on how to successfully repack the wheel bearings on your trailers. After removing the bearings and rear seals, check for dirt and debris on the bearings. Clean bearings are a must. Brake cleaner works great for that job. Flat spots or scratches on the bearings signal replacement. Never replace the cone without replacing the race--they grow up together. Pack the grease into the face of the bearings until grease is seen on the bearings. A packing cup to help pack the bearings is available at auto stores. Clean the axle before reinstalling the hub, bearings and seal. Here is one last tip on how to finish the job: Always overtighten the castle nut so that “rolling torque” is snug. Then, back off the nut until there is no end play, and the wheel rolls freely. Sometimes, when you find that exact “sweet spot,” the cotter pin will not align with the hole. When this happens (which seems like always), loosen the nut until the pin fits the next hole. Finally, take off those greasy gloves.

Q: I did some shop work on my disc to reinforce the area where the cylinder mounts. I made it stronger, but the problem I now have is that the single lift cylinder will not fit the way it was made. In other words, the end coming out of the cylinder is now at the bottom instead of the top. Everything fits perfectly, but it will not raise the disc like it did before I reversed the placement of the cylinder. I am using the same tractor and cylinder on the disc, so I know there is nothing wrong with my tractor or cylinder. Do you have any suggestions as to what is going on here?

A: Your problem is coming from the fact that you have decreased the lifting power of your cylinder when you reversed it. The rod end of the cylinder has more lifting power than the other end because the surface on the “donut” in the cylinder on the back side (where the pressure is applied to push out the rod) is much greater than the surface of the donut on the rod end. The more area that is available to be pushed by the pressurized oil, the more the cylinder will lift. So, in order to fix your problem, you will either need to increase the pressure on your tractor’s hydraulic system, increase the size of the cylinder or do some more work on your disc so you can return the cylinder to make sure the extending end is doing the pushing to raise the disc. A bigger cylinder will probably be the easiest fix if your cylinder cannot be reversed without a new design.

Safety Tip of the Month:

As an operator of machinery, always be sure all persons around the machine are seen or heard before starting a piece of equipment. Harvest time is a hectic “hurry up, got-to-go” time around the farm, and it’s easy to go without checking. Just recently, we removed the straw spreaders to look inside and set the chaffer sieve. As we were reinstalling the straw spreaders, the operator started the combine and turned on the separator. The rubber slingers slapped around onto the belly of the installer--about two seconds away from disaster. The operator should have never started the machine until everyone around the machine was seen. We are lucky to be harvesting good wheat but luckier not to have had a very bad accident.

Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


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