Anything with ball bearings needs maintenance, so don’t forget your Shimano freehub.
The freehub, as it’s called to distinguish it from the traditional freewheel that threads onto the hub, has a total of 50 1/8″ bearings on two races, upper and lower.
The upper race is unavailable for maintenance (bearing replacement) unless you take apart the entire freehub, which is no easy task. RJ the Bike Guy shows you how to do it, if you’re interested. You’ll need a special tool, which he shows you how to make. RJ couldn’t find the specialty removal tool online, nor could I.
Personally, I wouldn’t bother. A new freehub costs about $32.
However, cleaning the freehub can add to its lifespan. That’s an assumption. I can’t prove it, but based on experience with similar situations, I suspect it’s true.
That means removing the freehub from the wheel. You’ll need a 10 mm Allen key. I recommend a socket wrench with a 10 mm fitting because the freehub is usually on tight and you’ll need leverage.
RJ the Bike Guy takes you through the process in his video.
I’m not a fan of using solvents for cleaning, so I use Simple Green, an alkaline aqueous solution that does a great job. Just let it sit for a while, rinse the freehub with water and then dry thoroughly.
Note that while Simple Green is more environmentally friendly than solvents, it should still be disposed of according to hazardous waste rules in your area. Don’t dump used Simple Green filled with bike grease sludge down the drain.
I added some car oil to soak onto the top bearing race and car grease in the lower bearing race before putting back the lower race’s rubber O-ring. Be sure to install the O-ring the way it came out. Instructions show the correct orientation.
My freehub is four years old and has about 24,000 miles. I haven’t noticed any problems and the bearings look fine.
As an aside, I wonder why Shimano would say “Fabrique au Japon” on its packaging? I can only speculate it has to do with France’s law mandating the use of French under the Toubon law passed in 1994.
Instructions include English, Japanese, German, French, Dutch, Spanish, Italian, Swedish. Speak some other language? You’re out of luck.