I saw a post some time back when folks were discussing gear oil. My 351 has to be changed. I saw references to certain gear oils eating at yellow metals. Does a 350 tranny have any yellow? THis tractor will not be a working tractor. Couple of tractor rides a year, and maybe a half day of plowing. My main concern is leaks. I don't have much for leaks now and don't want any. The stuff I took out of the rear end was the color of Latte and poured pretty easily. Bomgaars (where I will probably buy) had 85w-90 and 85w-140. It is about $10 a gallon and the 140 was gl5. I hear they carry straight 90w mineral but I did not see it. If I find it, is it the best choice. I know this will bring a lot of opinions. That is ok. That is why I like belonging to this site.