im told that this binding is due to the gears not being perfectly round, and is quite normal. i tend to set the mesh and then check it at 90 degree intervals on the spur and set it at a comprimise if theres a difference in mesh. after the 1st couple of runs i recheck and reset it if need be, as its then run in the gears a bit. no lube is needed on the spurs or pinions, mate, they are self lubricating.

for the diffs, use the stickiest grease u have in the garage, or u can buy the proper stuff. dont use much on either the little planet gears or on the large crown gear - excess will just fly off. the diffs are not sealed so wont hold fluid.