Castrol TranSynd 668 Full Synthetic Automatic Transmission Fluid
Allison TES 668 Approved Transmission Fluid for On-Highway Allison Automatic Transmissions
Castrol TranSynd 668 is a full synthetic automatic transmission fluid formulated specifically for Allison on-highway automatic transmissions. It carries Allison TES 668 approval and is fully backward compatible with applications requiring Allison TES 295 and TES 468 fluids.
TranSynd 668 is engineered to provide wear protection, friction stability, thermal and oxidative resistance, cold-temperature performance, and consistent shift quality throughout the service interval. It is designed for demanding commercial and fleet applications where transmission protection, fluid life, and reliable operation are critical.
Key Benefits of Castrol TranSynd 668
- Full synthetic formulation for Allison automatic transmissions
- Allison TES 668 approved
- Backward compatible with TES 295 and TES 468 applications
- Improved gear protection
- Extended anti-shudder durability
- Extended clutch-friction durability
- Stable friction characteristics for smooth, consistent gear changes
- Strong thermal and oxidative stability to help control deposits and oil thickening
- Shear stability to help maintain viscosity during service
- Resistance to corrosion and foaming
- Cold-flow performance for lubrication during low-temperature starts
- Helps maintain transmission cleanliness and support extended service intervals
Castrol also notes that reduced friction can help control transmission-fluid temperatures, supporting fluid and component life.
Allison TES 668 Approval and Backward Compatibility
Castrol TranSynd 668 is approved to Allison TES 668.
It is also fully backward compatible with applications requiring:
- Allison TES 295
- Allison TES 468
This makes TranSynd 668 an upgrade option for many Allison transmissions that previously specified TES 295 or TES 468 transmission fluid. Always confirm the required fluid specification and service interval in the current Allison or equipment-manufacturer documentation before changing fluids.
Applications
Castrol TranSynd 668 is specifically formulated for Allison on-highway automatic transmissions requiring an approved TES 668 fluid.
Typical applications may include Allison-equipped commercial and fleet vehicles such as:
- Heavy-duty trucks
- Buses
- Refuse vehicles
- Delivery and vocational vehicles
- Other on-highway equipment using compatible Allison automatic transmissions
Use TranSynd 668 only where the transmission or equipment manufacturer specifies TES 668 or permits a backward-compatible TES 295 or TES 468 fluid.
Typical Technical Characteristics
| Property |
Typical Value |
| Kinematic Viscosity at 40°C |
33 mm²/s |
| Kinematic Viscosity at 100°C |
6.9 mm²/s |
| Viscosity Index |
168 |
| Brookfield Viscosity at -40°C |
<12,000 cP |
| Flash Point, COC |
>210°C |
| Pour Point |
-51°C |
| Appearance |
Bright & Clear |
Typical characteristics are provided for reference and should not be treated as product specifications.
Castrol TranSynd 668 FAQ
What is Castrol TranSynd 668?
Castrol TranSynd 668 is a full synthetic automatic transmission fluid formulated for Allison on-highway automatic transmissions. It is approved to Allison TES 668 and designed to provide wear protection, friction durability, thermal stability, cold-flow performance, and consistent shift quality.
Is Castrol TranSynd 668 approved for Allison TES 668?
Yes. Castrol TranSynd 668 carries Allison TES 668 approval.
Is TranSynd 668 backward compatible with Allison TES 295?
Yes. Castrol identifies TranSynd 668 as fully backward compatible with Allison TES 295 applications.
Is TranSynd 668 backward compatible with Allison TES 468?
Yes. TranSynd 668 is also fully backward compatible with Allison TES 468 applications.
Can Castrol TranSynd 668 replace TES 295 transmission fluid?
Yes, in Allison applications where TES 295 is specified and the applicable transmission or equipment requirements permit the use of a backward-compatible TES 668 fluid. Castrol identifies TranSynd 668 as backward compatible with TES 295 applications.
Is Castrol TranSynd 668 full synthetic?
Yes. TranSynd 668 is a full synthetic automatic transmission fluid.
What are the benefits of Allison TES 668 transmission fluid?
TranSynd 668 is designed to provide gear protection, anti-shudder durability, clutch-friction durability, oxidation resistance, shear stability, cold-flow performance, corrosion and foam resistance, and consistent shift characteristics.
Is Castrol TranSynd 668 suitable for cold-weather operation?
Yes. TranSynd 668 is formulated for strong low-temperature fluidity. Its typical pour point is -51°C, and its Brookfield viscosity at -40°C is listed at less than 12,000 cP.
How often should Castrol TranSynd 668 be changed?
TranSynd 668 is designed to support extended service intervals, but the correct fluid-change interval depends on the Allison transmission model, vehicle duty cycle, operating conditions, and maintenance requirements. Follow the current Allison and equipment-manufacturer service recommendations.
Where can I buy Castrol TranSynd 668?
Castrol TranSynd 668 is available for purchase online from Petroleum Service Company in 3-pack 1-gallon cases, 5 gallon pails, and 55 gallon drums. Select the appropriate package size on this page to review current pricing and shipping options.
For additional application, performance, and safe-handling information, refer to the current Product Data Sheet and Safety Data Sheet.
