Gear Oil choices for 1960-1966

[AnlaufJohn]

As my 1966 C-10 approaches the year-end, I will be treating it to some new transmission and differential lubricants.

The auto shops keep guiding me to the 85w-90 gear oils and I know it's been around for some time.

The factory manuals say to use 80 or 90 mineral oil, but no multi-viscosity or EP oils.

What is the consensus of this group?

I remember having to hunt down straight weight mineral oil for my Fiats back in the 80's. Do I need to find another Kendall Oil distributor?

AnlaufJohn in Springfield, Oregon

This is my truck's better side.

[63 & 64 Bowties]

I had the rear in my 64 rebuilt with new ring & pinion about 5 years ago by a guy I consider an expert. He builds racing engines and trans for a living, has his own shop. He added Amzoil, swears by it. BUT, I got new gaskets and seals, so take it for what it's worth.

[62gmc910]

Originally Posted by AnlaufJohn

As my 1966 C-10 approaches the year-end, I will be treating it to some new transmission and differential lubricants.

The auto shops keep guiding me to the 85w-90 gear oils and I know it's been around for some time.

The factory manuals say to use 80 or 90 mineral oil, but no multi-viscosity or EP oils.

What is the consensus of this group?

I remember having to hunt down straight weight mineral oil for my Fiats back in the 80's. Do I need to find another Kendall Oil distributor?

AnlaufJohn in Springfield, Oregon

This is my truck's better side.

The diff is the same as a '79 12bolt and I am pretty sure they spec 80-90 or something like it . If it is an open diff just go with gl-5 if its a posi penzoil makes an oil that work with GM clutch packs, I think the reason for specing straight weight oil was multi grade wasn't out yet. the oil with posi additive makes the trans shift a tiny bit smoother