Posted by Matt Wilson [172.69.69.175] on Thursday, April 12, 2018 at 22:14:03 :
In Reply to: Gearbox revisited posted by jim lee [172.68.142.44] on Thursday, April 12, 2018 at 20:42:31 :
My understanding is that Glyptal is supposed to seal off the inside of the transmission housing (and other castings) to keep oil from weeping through porous castings.
Another reason I've been told for the use of glyptal is to allow debris/particles to fall to the bottom of the case, since the glyptal is fairly slick. That way, those particles will drain out with the oil during an oil change. Otherwise, the particles tend to stick more readily to rough as-cast surfaces and could end up in the oil again, causing wear to the moving parts. I'm not sure how much I believe this reasoning, but it's though-provoking, nonetheless.