Recommended gear oil '71 4WD Blazer

[Joe Blaze]

I wanted to check the fluids before the winter on my '71 Blazer 4WD. Can anyone advise what are the modern day equivalents of the recommended front and rear end gear oil, and the transfer case fluid? I would be topping off, not changing out fluid.

Thanks

[1972RedNeck]

I would put 80W-90 In all of them with maybe a quart of ATF in the transmission/T-case for extremely cold weather.

[mrein3]

Originally Posted by 1972RedNeck

I would put 80W-90 In all of them with maybe a quart of ATF in the transmission/T-case for extremely cold weather.

I agree on the diffs. 80w-90. Make sure you don't have posi. If you do you'll need to add some friction additive.

The stock transfer case should be a NP205. I've seen GM specs for that unit that specify 80w-90 and Automatic Transmission Fluid (ATF). Nothing changed, just the spec printed by GM.
I've been running ATF because it works better when its -20 fahrenheit and you need to push the snow off the driveway.

[Joe Blaze]

Would it make a difference if I have automatic transmission?

[Joe Blaze]

Originally Posted by mrein3

I agree on the diffs. 80w-90. Make sure you don't have posi. If you do you'll need to add some friction additive.
...

How would I be able to tell if I have posi?