Upgrade or repair the transmission cooling in your 2006-2007 Chevy/GMC 6.6L LLY/LBZ Duramax with new Direct-Fit Transmission Coolers & Lines. Get OEM replacement cooler lines or performance braided hoses with billet -AN fittings for your vehicle. Replace the problematic factory thermal bypass valve (if equipped) with a performance transmission cooler thermal bypass valve. Most aftermarket transmission cooler give you greater cooling efficiency by an increase in core volume and fluid capacity. There are many high-quality manufacturers accessible, including Dorman, Mishimoto, BD-Power, and others.