Positraction Fluid

[VELCRO]

I am putting a different rear end under my '58. It is a posi unit out of another '58, does anyone know what was used for lubricant in these units.
Truck is a half ton.
I looked in 3 books and on line and found nothing but info for the standard rear end which I think used 90 weight.
I would appreciate some input on this.
Thanks

 

[rick az]

Generally speaking, old GM positraction units used 90 weight oil and a small bottle of additive that can be purchased at any GM parts counter. Just to be on the safe side, you might want to purchase a service manual from CD and see what it says about this subject.