Do NOT use any synthetic transmission oil / grease in a transmission with a Borg Warner Overdrive. The rollers inside of the O/D transmission that free wheel and lockup the transmission will be too slick with the synthetic oil causing the O/D to not lockup. If someone has installed the synthetic transmission lube, you will have to remove the transmission and disassemble it completely and clean all of the individual internal parts. You CANNOT flush out the transmission with it in the car and get all of the synthetic transmission fluid out of the transmission. So use ONLY non-synthetic transmission lubricant as per factory original or modern 80/90 non-synthetic gear lubricants.