Products Showing Parts for — {{ }}

No Results Showing Parts for — {{ }}
USD 57.92

Castrol Transynd 668 Full Synthetic Transmission Fluid

PART# Transynd668 | SKU METRANSYND668
★★★★★ ★★★★★ 5.0 (3 Reviews)

Vehicle Fitment:
For Allison 1000 & 2000 Transmissions (1 Gallon Bottle) | See full application list below
Buy now, pay later using Affirm Logo during checkout.
Ground Delivery by ,
If you order within hr min
This product cannot be shipped to your destination
Not Shipping to ?
Need it faster?
Our Recommendations Compatible Products
Scroll to View More


The Castrol Transynd 668 Full Synthetic Transmission Fluid is specifically engineered to get the most life out of your Allison 1000 or 2000 Transmission. Transmission fluid can feature a number of great additives, but if the base of the fluid is petroleum, it will not have the thermal resistance your Allison trans needs. Overtime, petroleum-based fluids react to oxidation quickly which overwhelms the effectiveness of the dispersants and detergents. The oil thickens and becomes more acidic which results in mechanical stress. Mechanical stress then leads to shear and results in permanent viscosity loss. Thinner oil results in decreased lubrication and increased friction. Sludge and varnish deposits erode shift quality and clutch durability, which results in increased component wear.

Unlike conventional petroleum-based fluids, this transmission fluid will not thicken and become acidic leading to viscosity loss. The performance additives in this fluid are tailored to the unique molecular structure and excellent antioxidant properties of this pure synthetic lubricant. This results in a lubricant with that is more physically and chemically stable than conventional oils and virtually is immune to shear. This specially formulated automatic transmission fluid transmits energy between the engine and the torque converter, eliminates heat, lubricates, improve seals, protects, and maintains constant friction properties between friction plates and reaction plates. 

Another great benefit of full synthetic transmission fluids is that they allow for extended drain intervals. TranSynd transmission fluid helps reduce maintenance costs and downtime on your Duramax. By lengthening the time between drain intervals, you save on the cost of transmission fluid, replacement filters, and the hassle of disposal. The greatest benefit of synthetic transmission fluid is the reduced wear, improved performance, and longer service life make Transynd the ideal Allison 1000 transmission fluid.

The TranSynd fluid features an Allison TES 668 approval. The TES 668 spec is fully backwards compatible for Allison TES 295 applications, but is not backwards compatible for TES 468 applications.

  • Fully Synthetic ATF
  • Improved Gear Protection
  • Allison Transmission Fluid
  • Extended Transmission Life
  • Longer Oil & Component Life
  • Extended Anti-Shudder Durability
  • Outstanding Cold-Flow Properties
  • Upgraded Clutch-Friction Durability
  • Prevents Deposits & Oil Thickening
  • Optimized Frictional Characteristics
  • Excellent Corrosion & Foaming Resistance
  • Formulated From Pure Synthetic Lubricants
  • Superior High-Low Temperature Performance


  • MPN Transynd668
  • ID 81903
  • Manufacturer Name Allison Transmission
  • Shipping Weight 8.00 lb.
  • Shipping Length 11 in.
  • Shipping Width 8 in.
  • Shipping Height 4 in.
  • Fuel Type Diesel
  • Prop 65 Prop 65 WarningWARNING: Cancer & Reproductive Harm -
  • Internal L19R34


★★★★★ ★★★★★
5.0/5 Stars out of 3 Reviews
Verified Buyer
They even ship fluids with no problem.
I needed 2 gallons of Transynd 668 to change fluid after replacing speed sensor in my 2006 GMC 2500hd transmission. They shipped it fast and had a good price. Order #2179595
Verified Buyer
Good products. I received everything fine.
Verified Buyer
Allison transmission fluid
Bought 3 gallons to do my transmission fluid change on my 2015 Chevy Duramax. Owners manual says it takes 7.4 quarts to do a drain and fill with spin on filter change...but mine took 10 quarts. I also dropped the pan and cleaned all the sludge out and put in a new internal filter.

Write a Review

Include Your Order Number For a Chance to Win a $100 Gift card

Overall Rating

Your Information

Email Address will not be made public.

Questions and Answers

No questions about this product. Be the first to ask a question!

Ask a question about this product

Please allow up to 1 business day for reply.

More to Consider

Recently Viewed


Complete the job with these highly suggested add-on products.

Product prices marked with an * may require additonal fees, such as a core charge, which will be displayed in the cart.