I spent a lot of time researching what oil to use in my t-5.I called GM service centers and asked them what i should use,they said ATF.
I purchased a couple of different s-10 factory manuals off of ebay and they say use the ATF.
I called several transmission shops and the rebuilder of my t5,they all said ATF.
Do a search on this subject and you will come up with pages to read.

I agree with joe,follow what the manuals and manufactures say.

1951 3100 Chevrolet
1951 Chevrolet Suburban Carryall
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