Allison 1000/2000 Torque Converter 6.6L Duramax 8.1L

Replacement heavy-duty torque converter for the Allison 1000 and 2000 series (AT1000/AT2000) automatic mounted behind the 6.6L Duramax diesel and the 8.1L Vortec gas engine in GM 2500 and 3500 HD trucks. It measures 13.25 inches across the cover, uses a 25-spline turbine to match the Allison input shaft, and bolts up with the factory 6-pad flexplate pattern. Shipping weight is 49 lb, so plan a helper or a jack when you cradle it back into the bellhousing.

The converter is the coupling between the engine and the gearbox: it carries the stall, engages the lockup clutch on the highway, and feeds line pressure back to the pump. On a rebuild you replace it rather than reuse the old one, because a rebuilt trans that keeps a contaminated converter just pumps the old clutch material and metal right back through the new frictions. Flush the cooler and lines before install, prime the converter with fresh fluid, and make sure it seats fully onto the pump hub and stator support before you draw the transmission up to the block.

Reach for a fresh converter when you have a slipping or shuddering lockup clutch, a code for the TCC circuit, gray metallic fluid after a failure, a converter that will not fully seat, or high stall from a worn stator sprag. Two-year limited warranty against defects in materials and workmanship when it is installed correctly and the cooler system is cleaned.