I'm going to add something here- I've had Selectros on my factory Dana 60 on my M715 and had a set go bad on me. The instructions caution about too much grease. Then I lost another hub. What ended up keeping them alive is to fill the truck's wheel hub with grease so that the splined axle stub is sticking out of a nice full pack of grease allowing the grease to be pulled at by the Lockout hub and no question of lubrication. Do NOT go crazy with grease inside on the mechanism of the locking hub or it can pack, jam and not work.
I've done this SAME THING on my Rockwell axles I then swapped into that M715 and packed the grease right out to where the Lockout itself bolts onto the spacer provided with the lockout kit. Fill that spacer to the end so that you even have a squeeze of grease push out when you install the outer lockout piece and bolt it all together. I've put at least 6,000 miles on those hubs with zero problems and they are similiar in design.