When HPP teamed with GM Performance Parts (GMPP) and Classic Restorations to mate the new THM 4L85-E SuperMatic transmission to a built-to-the-hilt SD-455, we wanted to fully document the process.

•Previously, we took you through the necessary steps for installing a modern electronically-shifted 4L60E trans into your third-gen. But we only got you half way there. This month we made a trip over ...