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.
Affected vehicles include model-year 2019-20 Ascent SUVs and model-year 2020 Legacy wagons and Outback cars. A programming error in the transmission control unit may ...