Get the Direct-Fit Transmission Coolers & Lines that will upgrade and fix the transmission cooling in your 2020-2023 Chevy/GMC 6.6L L5P Duramax. Get OEM replacement cooler lines or performance braided hoses with billet -AN fittings for your vehicle. Most aftermarket transmission cooler give you greater cooling efficiency by an increase in core volume and fluid capacity. Replace the problematic factory thermal bypass valve (if equipped) with a performance transmission cooler thermal bypass valve. There are many high-quality manufacturers accessible, including Dorman, BD-Power, Mishimoto, and others.