8HP70 Transmission Cooler 2011-2015

This is a used factory transmission oil cooler for the ZF 8HP70 eight-speed automatic, listed for 2011-2015 applications. It is the plate-style heat exchanger with its end housing still attached, and it ships with the ports capped. Buyers looking for it usually have ATF seeping from the cooler body or its fittings, a cooler that was damaged during engine or transmission work, coolant and ATF that have started to mix, or a transmission that runs hotter than it should and has begun to shift harshly once fully warm.

What the cooler does on an 8HP70

The 8HP is sealed for life and has no dipstick, so it depends on a tightly controlled fluid temperature. ATF leaves the case through the cooler feed, passes through the heat exchanger, and returns to the transmission. The housing on one end of this unit is part of the cooler assembly, so compare it with the one on your old cooler before you order. The 8HP70 is the higher-torque member of the first-generation 8HP family, used behind larger engines, so it puts more heat into the fluid than an 8HP45 behind a four-cylinder. A cooler that leaks, clogs or is blocked lets that heat build, and ZF notes that high temperatures shorten the life of LifeguardFluid 8 and call for shorter service intervals.

Symptoms of a failing 8HP70 cooler

• ATF wet on the cooler body, the line connections or the area below them after a drive
• Fluid level that drops over time with no pan or mechatronic sleeve leak found
• Milky ATF or ATF in the coolant reservoir, the sign of an internal leak in an oil-to-coolant exchanger
• Transmission temperature climbing higher than normal in traffic or when towing
• Harsh or erratic shifts that appear only when the fluid is fully hot
• Physical damage such as a cracked end housing or bent mounting tab

How to confirm before you buy

Clean the cooler, its lines and the transmission case, then drive and look again. On the 8HP the line connections are sealed with O-rings, and BMW issued a bulletin for O-ring leaks at the transmission-side cooler line connections on several 8HP cars, telling technicians to replace the lines and O-rings together because O-rings alone can come back. So find out whether the wetness starts at a line joint or at the cooler itself before you replace the cooler. Check the coolant for ATF and the ATF for coolant. Because the 8HP has no dipstick, a low-fluid complaint has to be confirmed with the correct temperature-controlled level check from the fill plug. Our ZF8HP common problems guide covers the mechatronic sleeve leak and other faults that look like a cooler problem, and the BMW 8HP problems guide covers the cooler line leak in more detail.

Fitment

The listing covers 8HP70 applications from 2011 to 2015. Transmission coolers are vehicle-specific, not transmission-specific: the same 8HP70 can sit in very different chassis with different cooler shapes, port positions and mounting points. Before ordering, compare the part number stamped or labeled on your old cooler with the one on this unit, and check that the port layout and end housing match. If you are not sure, send us your year, model and VIN and we will check it for you. You can browse every part we stock for this transmission on the ZF 8HP collection page.

Install notes

• Use new O-rings and seals at every cooler connection. Do not reuse the old ones; that is where most 8HP cooler leaks start.
• Flush or inspect the cooler lines. If the old transmission shed debris, do not route it back through a replacement cooler.
• Refill only with ZF LifeguardFluid 8 or the carmaker's approved equivalent. Our LifeguardFluid 8 service fill covers the fluid lost during the swap.
• Check the level the factory way: engine running, fluid between 30 and 50 C, fill at the plug until it just runs out, then refit the plug.
• If the fluid is old or burnt, the job is a good time to do the full 8HP70 service kit with pan, filter and ATF.
• If coolant got into the ATF, replace the fluid completely and inspect the transmission before trusting it.

Because this is a used part, inspect it on arrival, pressure-check it if you can, and confirm the end housing is intact before you install it.

Will this cooler fit my 8HP70 if my car is from a different maker?

Probably not. The 8HP70 went into several makes, but each car uses its own cooler shape, port positions and mounts. Match the part number on your old cooler to this one, or send us your year, model and VIN and we will check fitment.

Is my leak the cooler or the cooler lines?

Clean everything and recheck after a drive. On the 8HP the lines seal with O-rings at the transmission, and that joint is a known leak point. If the wetness starts at a line connection, replace the line O-rings (and the lines, if they are damaged) before changing the cooler.

What fluid do I use after replacing the cooler?

ZF LifeguardFluid 8 or the vehicle maker's approved 8HP fluid. Do not mix in a generic multi-vehicle ATF. Top up at the fill plug with the fluid between 30 and 50 C until it just runs out.

How much fluid will I lose?

Only what drains from the cooler and lines, usually far less than a full pan service. Since the 8HP has no dipstick you still need to do the proper level check at the fill plug afterward, because low fluid on this transmission causes harsh shifts and slipping.

Should I replace anything else at the same time?

Always new O-rings at every cooler connection. If the fluid is old or burnt, do the pan and filter service now. If coolant has mixed with the ATF, a full fluid replacement and a transmission inspection are needed.

Is this cooler new?

No. It is a used OEM part with the ports capped. Inspect it on arrival and pressure-check it before installing if you have the means.

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