Transmission Oil Cooler Line by Dorman®. Location: From Radiator to Cooler Inlet. Inlet and Outlet. Replacing a damaged cooler line with Dorman’s Auto Trans Oil Cooler Hose Assembly takes you a long way in protecting your transmission. Dorman’s line’s leak-resistant design prevents the common, high-stakes problem of transmission fluid loss. Plus, its robust construction readily defends against possible damage from road debris and corrosion.