I did for a while. It shifted great when the fluid was cold. However the trans did not last. In fact I broke 2 of them in a very short period of time. I have gone back to regular gear lube now. My theory is in 1970 the metalurgy was not what it is today and needs the original style gear lube. If it is a new trans or replacement or has new technology gears in it synthetic may be ok. Check with the supplier of the trans or replacement gears 1st.
I've got Red Line Synthetic in my Muncie and I love it. Recomended by the guy who rebuilt it, said it would drop the temp 50-70 degrees! I don't know about the temp cause I don't have a gauge for it, but it shifts like butter.... o No:
