A750E Transmission Cooler

If your Tacoma, 4Runner, Tundra, Sequoia or FJ Cruiser with the A750E five-speed is dripping red fluid at the front of the truck, the cooler fins got pushed in by a branch or a deer, or the old core is so packed with debris after a failure that you would rather not trust it, this is the replacement core. It is a used original-equipment A750E transmission oil cooler, the plate-and-fin air-to-oil style shown in the photo, with its mounting brackets and both hose spigots still on it. The listing carries the reference A064. Used means it came off a running vehicle, not off a shelf of reproductions, so the bracket spacing and tube ends are the factory shape.

What the transmission cooler does in an A750E

The A750E is Aisin's five-speed rear-drive automatic (the A750F is the same gearbox with four-wheel drive). Every bit of heat the torque converter and the clutch packs make ends up in the fluid, and the cooler is where that heat leaves. Fluid exits the case through a steel line, runs through this core in the airflow at the front of the vehicle, and returns to the transmission. Toyota fills the A750 with ATF WS, a low-viscosity fluid, and keeping it in its normal temperature window protects the clutch frictions, the converter lockup clutch and the solenoids in the valve body. When the cooler leaks, the transmission loses fluid with no warning light. When it is crushed or plugged, fluid runs hotter on every climb and every tow.

Symptoms of a bad A750E cooler

• ATF drips or a wet film on the cooler core, its hose ends, or the splash shield under the front of the truck.
• Fluid level that keeps dropping between checks with no leak at the pan or output seal.
• Bent, flattened or corroded fins, or a core packed with mud, bugs or seed after off-road use.
• Shifts that soften or flare once the truck is hot, especially towing or climbing, because low or overheated fluid lets the clutches slip.
• Dark, burnt-smelling fluid sooner than it should be.
• Metal or clutch debris left inside the old cooler after an internal failure, which will be pumped straight back into a rebuilt unit if the core is reused.

How to confirm the cooler is the problem

Clean the area first, then run the truck and look. A leak at the crimped hose ends can be fixed with new hose and clamps, so make sure the seep is coming from the core itself before you replace it. If the transmission has already come apart with burnt clutches or a failed converter, the cooler is suspect even if it does not leak, because the passages trap debris. Our guide on how to flush a transmission cooler after a failure covers when a flush is enough and when a plate-fin core like this one should simply be replaced. If the truck runs hot without any leak, read why Aisin units overheat before you buy, since a low fluid level or a dragging converter clutch will cook fluid no matter how good the cooler is.

Fitment

This cooler is listed for the A750E. Toyota used that transmission in the 2003-2009 4Runner V8, 2005 and later 4Runner V6, 2005-2015 Tacoma V6, 2004-2009 Sequoia, 2005-2009 Tundra and the FJ Cruiser, with the A750F in the four-wheel-drive versions of many of the same trucks. Cooler size, bracket layout and hose routing are not the same across all of those bodies and years, and some trucks carry a different core depending on the tow package. Before you order, compare the bracket positions and the inlet and outlet spigot locations in the photo against the cooler on your truck, or send us your year and VIN and we will check it for you. You can see every part we carry for these units on our Aisin and Toyota transmission page.

Install notes

• Put a drain pan under the front of the truck; disconnecting the hoses will drain fluid that is in the lines and core.
• Replace any cracked, swollen or oil-soaked hose sections and use new clamps. Old hose that has been heat-cycled for years is a common leak point right after a cooler swap.
• If the reason you are replacing the cooler is an internal failure, flush the steel cooler lines too, and change the filter at the same time with an A750E/A760E filter and pan gasket kit.
• Refill only with Toyota ATF WS, such as genuine Toyota WS fluid. The factory repair manual lists about 0.6 liters (0.63 US quarts) to replace what is lost when a transmission hose or pipe is removed; a full cooler swap can lose more, so top up and then check.
• The A750 has no dipstick. Set the level through the overflow plug with the engine idling and the fluid between 46 and 56 C (115 to 130 F), following the factory check procedure, then road test and look for seeps at both hose ends.
• If the transmission is coming apart anyway, pair this cooler with an A750E master rebuild kit so the new frictions start life with a clean cooling circuit.

Will this cooler fit my Tacoma, 4Runner or Tundra?

It is listed for the A750E, which was used across several Toyota trucks and SUVs, but the cooler core, brackets and hose positions vary by body and tow package. Match the bracket layout and spigot locations in the photo to the cooler on your truck, or send your year and VIN and we will confirm before it ships.

Is this a new or a used part?

It is a used original-equipment cooler removed from a running vehicle. That gives you factory bracket spacing and tube ends rather than a universal core that needs adapters.

What fluid goes back in after the cooler is replaced?

The A750E takes Toyota ATF WS. Toyota's repair manual lists about 0.6 liters to make up for a hose or pipe removal; replacing the whole cooler can lose more, so add fluid and then set the level at the overflow plug with the fluid at 46 to 56 C.

Should I replace the cooler after a transmission failure?

Usually yes. A plate-and-fin core traps clutch material and metal, and that debris goes straight into the rebuilt unit when the truck starts. Flush the steel lines and install a new filter at the same time.

Can a bad cooler cause slipping or harsh shifts?

Indirectly. A leaking cooler drops the fluid level and a plugged or crushed one lets the fluid run hot, and both let the clutches slip or flare when the truck is warm or towing. Fix the cooler and check the level before blaming the valve body or clutches.

• How to Flush a Transmission Cooler After a Failure
• Aisin Overheating: Why It Happens and How to Prevent It
• Transmission Cooler Types and How to Size One for Towing
• Toyota Camry and Tacoma Transmission Service: What the Dealer Won't Tell You