Since white lead has become viritually impossible to get, Prussian Blue is the best option for checking gear contact patterns. Another possibility is a tube of artist's white oil paint pigment and a few drops of linseed oil. Hold a rag wrapped tightly around the pinion flange to provide a little resistance while someone else moves the ring gear back and forth rapidly with a box end wrench on one of the attaching bolts. You'll get a much better representation of the actual contact pattern that way.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!