the owners manual calls for regular 30w castrol gtx, i understand. I am using a trans i pulled out of a '76 '02 that i bought as a parts car. i went to change the existing oil before putting the gearbox in my project car and found the gearbox had very little oil. The gearbox worked fine when i drove the car prior cannibalizing it. What weight oil do i use? I saw somewhere that somebody suggest atf.