Fasteners and Grade 8 Bolts, Oh My!
Let’s have a conversation about fasteners, specifically bolts for 4 speed transmissions, all of ’em, the ST10, Muncie trans of all flavors and Ford Toploaders.
I often see people advertising the use of grade 8 bolts on their manual transmissions.
I don’t think this is a good idea. In fact, I don’t know of any 4 speed transmissions in the 1960’s or 70s that used nor suggested a grade 8 bolt.
A bolt or fastener is designed to have a slight stretch, and locks onto the threads of its intended parts. A bolt fastening a transmission is only as strong as the aluminum housing to which it is attached. So, the use of a grade 8 bolt is counter productive at worst, and a waste of money at least.
I’ve dug out one of my vintage mechanic manuals covering bolts. Take a look at this table, so you can distinguish the standards of your Steel Bolts and Fasteners as they are outlined in the table above.