Find Aftermarket Transmission Coolers for the Sterling L-Series. Keep your truck's transmission cool and running smoothly with Sterling L-Series Transmission Coolers. Built tough for heavy-duty use, these coolers efficiently dissipate heat to protect your drivetrain and extend its life. With a variety of sizes and fitting options, there?s a cooler to match your truck?s needs?whether you?re hauling heavy loads or tackling tough conditions. Reliable performance for your powertrain starts here!