<snip> Is "Prussian Blue" the right stuff to use to see how the gears are touching? <unsnip> I use white artist's paint, diluted to a very thin milky level with motor oil. It's much more visible than the prussian blue. One little tube lasts a lifetime. If you want to read more about this, it's published in Bob Helt's book "The Classic Corvair". Craig (Just did two diffs) Nicol