Has anyone used Amsoil synthetic Transmission lube 75W-90 GL-4 in their 1969 4 speed?

I got 3 miles out of one filled with Passon's special blend. I didn't blame the lube. Fact is I strained out the metal and reused in the new trans Its got over 1000 miles on it and working fine.Still dont know why the first one "siezed" up. Just one of those things.