ALLISON 1000 Chevy GMC Duramax Diesel Transynd Fluid Transmission 1 gal Fits 2000-up Diesel Applications. For a "drain and fill", a minimum (of 2) gallons are necessary to complete the job refer to your vehicle owner's manual. Castrol TranSynd 668 Fluid Castrol TranSynd 668 is a premium, full-synthetic automatic transmission fluid specifically formulated for Allison Transmission® on-highway automatic transmissions. TranSynd 668 provides oxidative stability, anti-wear performance, and friction durability, as well as TES 668andtrade; specification differentiators such as extended anti-shudder durability and extended clutch friction durability. This fluid features an Allison TES 668 approval. The TES 668 spec is fully backwards compatible with TES 295® applications but is not backwards compatible with TES 468™ applications. Advantages Deliver improved gear protection. Delivers extended anti-shudder durability. Delivers extended clutch-friction durability. Excellent corrosion and foaming resistance. Excellent thermal and oxidative stability that helps to prevent deposits and oil thickening. Excellent transmission cleanliness under all conditions permits extended oil-drain intervals and decreased servicing. Excellent temperature reduction through reduced friction leads to longer oil and component life. Outstanding cold-flow properties enable faster oil flow to all critical components particularly during cold starts. Optimized frictional characteristics give smoother gear changing at all ambient temperatures and load conditions. Excellent shear stability properties help to retain full transmission performance over the entire oil-drain interval.