Ask The Mechanic

Change The Hub Oil

John Deere tractor front wheel drive hydraulic oil drain plug, Image by Steve Thompson

Q: I have a John Deere 5085E tractor with a front-wheel drive. It has a hub on the front wheels that seems to have an oil plug in the end. How do I check the oil in that housing, and should the oil be changed? The hub rotates with the wheels.

A: Yes, there is oil in that assembly, and it is called a planetary and gets its name from its design. It contains smaller gears that rotate inside a larger gear like the “planets” revolve around the sun. This design lessens the load while creating torque. Under normal use, I usually change the oil every two years. Here’s how you do it: Move the tractor until the drain plug (see photo) is at the bottom. Drain the oil and move the tractor until the plug is exactly horizontal with the ground to fill. Fill the planetary with JD hydraulic oil to this level, and install the drain plug.

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Q: I have a 504 Vermeer round baler that has a bearing out on one of the rollers. The roller is the one that raises up as the bale is being formed. The bearings fit in the roller ends, and the roller is bolted to the arm on each end. I can’t figure out how to remove the bolts that fit through the arms and screw into the roller bearings on each side. The sides of the side of the baler are in the way. What’s the trick? I don’t want to cut a hole in the sides of my baler.

A: Put the torch away! If you look near the top of the bale on each side, you will see a hole about the size of a tennis ball. The trick is to get the arm and roller, which will be under pressure when raised, to the top so the ends of the roller will be exposed through the hole. Dealers usually have an overhead crane or an “A” frame they use to raise the arm in order to change out these roller bearings. Out in the field, sometimes we use a loader or a big tree limb, and a come-along and chain above the baler to pull the arm up until we see the ends of the rollers through the holes. Now, you can remove the countersunk screws from the bearings. One more thing: These screws come with thread lock from the factory, and they will be extremely tight from both this material and the normal accumulation of rust. The countersunk screw is an Allen head, and you will probably have to heat the screw before it will break loose. An impact with an Allen socket works the best. Be careful: The roller is heavy.

Q: Is it important to set the valves on a Cummins engine in a Ram truck?

A: Yes, it is very important. Not setting the valves is like high blood pressure--it’s a silent killer. The valve timing also affects engine timing. I run the valves on my 1997 “Dirty 12” every 100,000 miles. The newer ones can go longer. Valve setting is critical on any engine.

Safety Tip of the Month:

Be very careful when working with hand grinders that do not have a paddle “panic” switch. Some grinders remain in the “On” position when you put the grinder down after a power loss. The best worst case is if you pull the cord out from the power source when stretching to grind a corner. We have all done this. Next, it’s easy to put the grinder down or hold it loosely in one hand when plugging back in while leaving the grinder switch on. Then, when you plug in the cord, the grinder suddenly takes off. Since an electric motor has instant torque, the grinder goes crazy. I bet many farmers out there (like me) have experienced the out-of-control grinder.

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


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