Good questions- - - - -and you're going to get a bunch of sometimes very different answers from the stovebolt crew. Opinions are like "noses"- - - -everybody's got one, and some of them are pretty smelly at times!
Brake fluid- - - -DOT 3 is good, DOT 4 is better. DOT 4 was developed to handle the higher temperatures encountered in disc brake applications, but either one will be OK for use in a stovebolt truck. RUN- - - -do not walk away from DOT 5- - - - -it's silicone based, and does not play well with other fluids, and possibly some of the rubber parts in a stovebolt brake system.
Gear lube- - - -straight 90 weight mineral oil for the transmission, Hypoid gear lube for the rear end. 90 weight in the rear end was the original specification, but multi-weight will work. Synthetic hypoid gear lube in a stovebolt transmission- - - -particularly the SM-420 4 speed, can cause gear grinding because it's too slippery to let the synchronizer blocker rings work properly.
Engine oil- - - -lots of opinions here, with everyone believing their prejudices are justified. I prefer using 15W-40 Diesel rated oil in everything I run from modern high-mileage vehicles to stovebolts, to my Harley and all the small engines on the farm. No oil-related engine failures in 40-something years of doing that. Don't try that on a brand new modern engine- - - -that's where the 5W-30 and 0W-30 oils are needed. Once even those engines get 100K + miles, a thicker oil is a good idea because of increased clearances from normal wear. 50 weight oil is for racing engines- - - - -it's foolish to run it in a street engine of any kind.
Jerry
