Just answered my own Q,
From Ody site -
The click you hear is each pawl of the cassette or freewheel as it springs out after each tooth has passed and it smacks into the trough between teeth. If you fill the mechanism with thick grease then it will “damp” this movement and cushion the impact of the pawl against the toothed part of the hub. So adding thick grease will quieten the hub substantially. Unfortunately if you over-do this then the pawl might not make it all the way back to position between each tooth and it might slip under load. Far from ideal.
If on the other hand, you clean out what grease there is in there, and replace it with just a very thin smear of thin oil, then there will be almost no resistance for the pawl and it will make the loudest click possible (and be less likely to skip or slip).
Between these two extremes there are an infinite number of options, different thicknesses of grease and oil will give varying degrees of damping and therefore sound level.
With cassettes and freewheels that use individual springs under each pawl, you can also bend these springs out a little to give more spring and so more noise (or less chance of slipping with a thicker quieter grease).
At this point it is useful to know that you can “thin” grease by mixing in more oil (grease is traditionally just an emulsion of oil and water with ‘soap’). Take your normal grease and mix in some WD40 or other thin oil and it will become thinner and less viscous.
While we are on the general subject, it is worth mentioning that all freewheels and cassette hubs need a little love now and again. If your freewheel or cassette hub is slipping or making nasty noises then it will need a bit of attention.
With freewheels, taking them apart IS an option but its not much fun so make it the last resort. Instead, just dripping some thin oil in through the crack between the toothed part and the “body” is often all it needs. And by “dripping some” I do of course mean “pissing a shed load”. With freewheels this oil needs to do the job of both cleaning and lubing so you need enough to wash any “crap” out the back. Keep spinning the freewheel to work it through and you should notice a dramatic improvement.
