What I've done to quiet freewheels is to run oil into the body until it comes out the other side. Wipe off the excess, and then seal the gap between the inner and outer freewheel body with a heavy grease. You're not packing the grease into the freewheel, just working it into the gap to seal the oil inside. Seal both sides of the freewheel this way. It's not permanent, but you can get several weeks or even months of silent running, after which you just repeat the process.