Automatic Transmission Oil Cooler Line Connector by Dorman®. Location: Transmission Fluid Cooler Pipe Fitting to Case. Quantity: 1 Piece. Thread: 5/16″. Dorman’s Auto Trans Oil Cooler Line Connectors are constructed from high-quality materials to provide a leak-free connection between transmission lines or between the radiator and the transmission. Replacement restores the radiator to proper operation.