Toyota Tundra Transmission Oil Cooler Thermostat 32970-34030

This is the automatic transmission oil cooler assembly with the built-in thermostat valve, replacing Toyota 32970-34030. It is listed for the 2007-2021 Toyota Tundra 5.7L V8, 2008-2012 Sequoia 5.7L, 2008-2016 Land Cruiser 5.7L and 2008-2016 Lexus LX570. These trucks use the Aisin AB60 six-speed automatic. The assembly is a cast aluminum housing with the two cooler hose nipples and the thermostat that decides when ATF is routed through the cooler.

The thermostat keeps fluid out of the cooler until the transmission is warm, then opens to send it through. If it sticks closed, ATF runs hot when towing or climbing and you may see high transmission temperature readings; if it sticks open, the transmission is slow to warm up in cold weather. The other common reason to replace this part is a leak at the housing or around the hose nipples, which shows up as ATF on the side of the transmission and a falling fluid level. Confirm the leak source with a clean, dry transmission before ordering.

To replace it, let the truck cool and put a drain pan under it. Clamp or plug the cooler hoses, loosen the hose clamps and pull the hoses off the old unit, then unbolt it. Clean the mounting surface, bolt on the new assembly, and install the hoses with new clamps if the old ones are weak. Top off with Toyota WS fluid and check the level using the fill and overflow plug procedure at the fluid temperature Toyota specifies, since the AB60 has no dipstick.