Tru-Cool LPD47391 40,000 GVW Heavy-Duty Stacked-Plate Transmission Oil Cooler with Mounting Hardware

Heat is what kills an automatic transmission, and nothing makes heat like towing a loaded trailer up a grade in the summer. The factory cooler built into the radiator tank is barely adequate on a stock truck and hopelessly undersized the moment you hook up. This is the cooler that has become the default answer to that problem: the 40,000 GVW LPD47391, the same low-pressure-drop stacked-plate design people just call the 40k cooler.

The trick is in the plates. Instead of a simple tube-and-fin core that chokes cold fluid and starves the transmission on a winter start, this one uses a brazed aluminum stacked-plate core with a low-pressure-drop internal path. It moves a lot of fluid through a lot of surface area without building the back pressure that a restrictive cooler creates, so you get roughly 30 percent more heat transfer while the transmission still sees the flow it needs. Lower fluid temperature is the single biggest thing you can do to make a transmission last, and this is how you get it.

It fits cars, vans, light trucks, RVs, and any tow rig, and it replaces the LPD47391, 47391, and OC-4739-1 part numbers. The kit ships with the full mounting hardware set, bolts, fasteners, and brackets, plus the nylon-tie style mounts to hang it in front of the condenser, so you have what you need to plumb it into the cooler lines and go. If you tow with an automatic and you have not added one of these yet, it is the cheapest insurance against a burned-up transmission you can buy.