Allison TES 668 full synthetic ATF in a 5 gallon pail, twenty quarts, sized for a full Allison 1000 or 3000 series fluid and filter service.
The five gallon pail of Castrol TranSynd 668 is twenty quarts of Allison TES 668 full synthetic, and it is the size for the bigger jobs: filling a rebuilt or replacement Allison 1000 from dry, refilling after a cooler or cooler line replacement on a Duramax, doing two drain-and-fills back to back to get an old unit off TES 389 fluid, or keeping a small fleet of HD pickups and medium-duty trucks serviced from one container. If you only need a pan service on one pickup, the smaller packs make more sense; if you are past that, the pail is the economical way to buy it.
Every Allison from the 1000 Series in a Silverado HD to a 4000 Series in a vocational truck uses the fluid to apply its clutches, cool the torque converter and lubricate the planetary gearsets. Allison launched TES 668 in 2020 and recommends it across the 1000, 2000, 3000 and 4000 Series. It is backward compatible with TES 295, TES 389 and TES 468 fluids. The practical benefit is the long change interval: 150,000 miles or 48 months on general duty and 75,000 miles or 36 months on severe duty with Prognostics off, versus 50,000 miles or 24 months for TES 389.
If fluid was lost because of a failure, find the cause first. A unit that went into limp mode, set codes or left metal on the filter magnet needs diagnosis, and our Allison 1000 limp mode guide is the starting point. Check for any trace of coolant: Allison allows condensation up to 0.2 percent water by volume, and any ethylene glycol means seals, frictions and solenoids have to be replaced.
TES 668 is approved for every Allison 1000 and 2000 Series unit, including the 2001-2019 Chevrolet and GMC 2500/3500 HD trucks with the Duramax or 8.1L and the Kodiak and TopKick, and for the 3000 and 4000 Series. On a 1000 Series, Allison lists an initial dry fill of about 14.8 quarts on a standard sump and 12.7 quarts on a shallow sump, before external lines and cooler. Refills are about 10.6 and 7.4 quarts. That means one pail covers a dry fill plus the lines, or two complete shallow-sump changes. The 3000 and 4000 Series hold considerably more; check the capacity for your model and sump in its operator's manual before deciding if you need a second pail. For a single pan service on a pickup, the one gallon size or three-gallon pack is enough. Pickup parts are on the Allison 1000 parts page.
Capacities and the interval table are broken down in our Allison 1000 fluid and filter service specs.
| Fluid specification | Allison TES 668 (supersedes TES 295) |
| Type | Full synthetic |
| Volume | 5 gallon pail (20 quarts) |
| Drain interval | Up to 300,000 miles / 48 months general duty; 150,000 miles / 48 months severe duty |
| Applications | Allison 1000, 2000, 3000 and 4000 series automatics |
Yes for the 1000 Series. Allison lists an initial fill of about 14.8 quarts on a standard sump and 12.7 quarts on a shallow sump, not counting external lines and cooler. Twenty quarts covers that with fluid left to set the hot level.
Yes. Allison recommends TES 668 fluid for the 3000 and 4000 Series. Those units hold considerably more fluid than a 1000, so check the capacity for your model and sump before ordering.
A single drain leaves old fluid in the converter, cooler and lines. If that old fluid was TES 389, Allison counts the result as a mixture on the short interval. A second change gets the unit close to full TES 668.
With 100 percent TES 668 or TES 295 and Prognostics off, Allison lists 150,000 miles or 48 months on general duty and 75,000 miles or 36 months on severe duty. Filters run a shorter schedule.
No. Allison calls for disassembly and replacement of seals, friction plates, solenoids that fail resistance checks and other parts when any glycol is found. Fix the transmission, then fill with fresh fluid.
