Red Line 75W140 NS contains extreme pressure additives like Red Line 75W140 GL-5 oil, but lacks friction modifiers to balance slipperiness. Extremely popular for historic and vintage transmissions, like Mid-1930s to early-1950s synchro-equipped gearboxes. An excellent option for noisy transmissions when mixed with Red Line 75W90NS or MT-90 to bring viscosity level up. Also used in clutch-type limited slip differentials in racing for maximum lock with the option to add Limited Slip Friction Modifier in small doses to customize slippage.