Freehub internals need a grease that solves a specific problem: it has to lubricate spring-loaded pawls that snap in and out under load, without gumming up their movement or migrating into places it shouldn't be. That's a different job than packing hub bearings, and using the wrong grease is one of the more common reasons a freehub starts skipping or losing engagement mid-ride. Shimano's FH-7800 Freehub Grease is the factory-specified fix, formulated specifically for the freehub bodies on Dura-Ace FH-7800 and FH-7801, Saint FH-M800 and FH-M805, and the more recent FH-MT500 and FH-MT510 hubs.

The consistency is the whole point. It's a light-to-mid weight grease with a soft, almost jelly-like feel — thin enough that the pawl springs can push the pawls back into position quickly, but tacky enough to stay on the ratchet ring and pawl faces instead of slinging off. Cold weather won't turn it into peanut butter and stall pawl engagement, and summer heat won't thin it to the point where it drips past the seals. If you've ever had a hub start ratcheting inconsistently in January, this is usually the fix.

Shimano is explicit that this grease is for freehub internals only. Don't pack hub bearings with it — reach for Shimano Premium Grease for that — and don't mix it with other lubricants inside the freehub body. If you're servicing a hub that's been packed with something else, clean the pawls, springs, and ratchet ring thoroughly before applying the FH-7800 grease so the formulation can do its job without interference.... Read More