I recently rebuilt my diffs. I found that wiping each gear off with a paper towel and even q-tips did not remove the old fluid in the valleys between each tooth. I planned to refill with kyosho diff grease and didn't want even a trace of the old fluid to dilute the grease. In frustration I left each gear with the teeth facing down on a clean paper towel overnight, thinking I would clean them in mineral spirits and a toothbrush the next day. The next morning each gear was spotlessly clean as the overnight "sit" had allowed the oil to slowly flow downward and be soaked up by the paper towel.

But, I'm wondering what I'm going to do when it's time to rebuild the diffs now that they have been refilled with grease, as I don't think it will flow downward like silicone diff oil.

Don