Can I use 75W90 Differential Oil in the steering Box?

[Fiat88]

I'm trying to figure out what kind of oil to use in the steering box and idler. I saw some old posts about using diff. oil. I have about a quart left of redline synthetic 75W90 Differential Oil, is that the right oil to use? Thanks.

[wikkid]

Should be fine. 75/90 is a little thinner than 80/90. but no big deal there. EP (Extreme Pressure), like the diff. oil, is needed.

It's only the transmission oil that needs to be GL-1 90w mineral oil.

[Fiat88]

Ok thanks.

[ace124]

Use ATF hydraulic fluid in the idler though, with a table spoon of stop leak.
The idler is a Hydraulic unit.