Abstract: A pinion for a center differential or speed reduction assembly of a motor vehicle transfer case includes external gear teeth and an axial passageway defined by alternating grooves and lands. The grooves and lands may be either axial or helical. The grooves provide improved lubrication and debris removal among other features. The pinion is preferably a powdered metal part.

Abstract: A method for preparing a suspension for coating a substrate with particles which includes determining a pH range in which the heterostability ratio of the substrate and the particles: ##EQU1## is less than 10.sup.10, the homostability ratio of the substrate: ##EQU2## is greater than 10.sup.10, and the homostability ratio of the particles: ##EQU3## is greater than 10.sup.10, wherein a.sub.1 is the radius of the substrate, a.sub.2 is the radius of the particles, V.sub.T is the total potential energy of the interaction between component i and component j, wherein i and j are the consecutive subscripts of the stability ratio being considered, T is temperature, k is Boltzmann's constant, and r is distance which varies from (a.sub.i +a.sub.j) to infinity. The suspension is useful for coating the substrate with the suspended particles by exposing the substrate to the suspension.