Is ACDelco 10-4033 transmission and transfer case fluid suitable for a SM420 transmission built in "I"1355. Sept13, 1955. It does have brass synchros.
I have seen it listed as 75W80 and also 75W90. It seems thinner when poured at 60 degrees F. I have seen it listed as mineral oil. I am not sure if it is GL-4 or GL-5 altho it has been alluded to being GL-4. And it is reddish in color.
It appears that the old Dexron III is listed as GL-3 even tho I have not seen it for sale - I do not know if this is true.
Fluid is too slick for syncro to work. G.M. sells manual transmission & transfer case fluid p/n 88861800 which is Dexron II in a new package.
Dexron II became Dexron llE which was became Dexron III. ATF is not the thing to use, HRL is spot on.
