TranSynd is a full-synthetic, automatic transmission fluid designed specifically for ALLISON transmissions.Castrol TranSynd 668 Synthetic Automatic Transmission Fluid, 5 gal Full-synthetic automatic transmission fluid designed specifically for ALLISON transmissions Meets TES 468 specifications, ensuring compatibility and performance Allows for extended drain intervals of up to 500, 000 miles / 48 months in normal-duty transmissions Suitable for severe-duty transmissions with extended drain intervals of up to 250, 000 miles / 48 months Provides 12 times longer drain intervals compared to conventional and non-TES 668 and non-TES 295 fluids