The Advance Adapters TH400-Atlas Adapter (SKU AS-6400) is a 4.25" spacer adapter built specifically for GM TH400 transmissions (also compatible with the 4L80E) that have a 4.5" output shaft stickout. This is a fitment-specific measurement, so confirming your transmission's output shaft stickout length before ordering is worth doing — Advance Adapters calls out the 4.5" figure specifically as the application this adapter is designed for.
What's included:
- GM T400/4L80E Gasket (716510)
- Adapter, TH400 to D300 (51-6400)
- H.H.C.S. 3/8-16 x 1-1/2" Grade 5 Zinc (723723)
- Lock Washer, 3/8 Zinc (723704)
This is a lean kit — gasket, adapter, and hardware, nothing extra — built for the specific TH400/4L80E-to-Atlas fitment where the 4.5" output shaft stickout matches. As with the other TH400 adapters in this line, confirming your transmission's exact output shaft stickout against this spec is worth doing before ordering.