What oil and how much Saginaw 4 speed?

[HAFROD]

A friend told me to use 80/90 gear oil but curious about a good quality one to use. Something off the parts store shelf that I don't have to order.

 

[DRIVEN]

80W90 should be fine. I know there has long been a debate over GL4 vs GL5 in older transmissions with brass synchros. Personally, I'd seek out some GL4 which Napa usually carries. As far as brands go, I've always been a Valvoline guy but any name-brand should be okay.

 

[Bonnewagon]

GM factory manual says 3.5 pints of 90 weight. In reality you fill up
to the bottom of the filler hole on the side of the trans case. I used to use heavy weight racing oil but found that in cold weather it affected "spin down" time and the gears clashed if I shifted too fast . I went back to straight 90 and that works best. Any decent brand like Castrol, Valvoline, or Pennzoil is fine.

 

[Artomatic]

I would recommend 80w90 .. I like royal purple .. For gears box rear diff .. Pretty much I like to spend the extra bucks knowing i won't have to mess with it for a while ..