Summer is upon us, bringing high ambient temperatures and the recreational towing season. Both can push your 7.3L Powerstroke’s 4R100 transmission to its thermal limits. Heat is the number one enemy of an automatic transmission, and keeping temperatures in check is the single best thing you can do for its longevity.

The solution is a transmission cooler upgrade, which can drop temperatures by 20-60 degrees Fahrenheit. Let's break down the two best options: swapping in a larger OEM cooler from a 6.0L Powerstroke or installing a complete aftermarket kit. We'll discuss the options specifically for Super Duty trucks; however, if you have an OBS, the 6.0L option will work, you'll just need to fabricate some mounting brackets. All else is essentially the same. We've also listed an option for 6.0L owners to get the same results, at the end. 

How it works & why an upgrade is crucial: From the factory, your 7.3L’s transmission fluid is cooled by two units. Fluid flows from the transmission first to a small cooler inside the radiator, then to a secondary, external cooler mounted in front of the A/C condenser before returning to the transmission. A note: the OEM 7.3 secondary cooler is an inefficient tube and fin design. The Mishimoto and 6.0 units are both stacked plate heat exchanger designs. Much more efficient than the tube and fin design.

Installation of the upgrades: This will be pretty much the same for either the 6.0L or Mishimoto unit. We’re simply removing the OEM secondary cooler and replacing it with the upgraded part. It’s as easy as draining the fluid, disconnecting the lines and the cooler, and swapping in the new (and refilling the transmission with new fluid). A 2hr install for most. Since the core support is essentially the same between the 7.3 and 6.0, the mounting tabs line up perfectly, no modifications needed.

One big tip: You’ll need to remove the hood latch to install the new cooler. Mark its location with a Sharpie so it’ll go back in the same spot. This’ll stop you from having to realign it upon reinstallation—a very tedious task.

The difference between the two routes: The Mishimoto is a 37-row cooler, so it has the ability to cool better than the 6.0’s 31 rows. The Mishimoto is also a complete kit, with no other parts to buy. Price-wise, they’re both pretty much the same at around $400 for new parts. If you can source a less expensive or used 6.0L cooler, you can accomplish this upgrade for less money than the Mishimoto route.  

As we said, the Mishimoto kit comes with everything you’ll need, whereas with the 6.0L method, you’ll need to source some parts.

Two 6.0 coolers are available, but most choose the larger 31-row cooler (Ford PN: 5C3Z-7A095-B). To install it, you’ll need three feet of ½” transmission hose, and you’ll need to adapt the fittings. The 7.3 has 3/8” inverted flare fittings, whereas the 6.0 uses 3/8” quick-connect fittings. A ½” hose will fit over the 6.0’s fittings using a couple hose clamps to secure them, then you’ll need to adapt them down to 3/8” to mate to the 7.3’s existing transmission lines. Adapters can be made in many ways, but the cleanest way is to use barb fittings like these: https://www.riffraffdiesel.com/transmission-cooler-7-3l-6-0l-ss-adapter-2/

In the end: Both routes have proven their worth on thousands of trucks. The biggest difference would be cost. If you’re strapped for cash, find a used 6.0 cooler, pick up some line and adapter fittings and you’re good to go. Just make sure the cooler is clean. If you can afford the Mishimoto route, it’s much easier and cools a little better. Either way remember you will need to add an extra couple of quarts of fluid as it’s now a physically larger system.

Helpful links:

Full 6.0 cooler install: https://www.powerstrokenation.com/threads/this-how-to-install-youre-6-0-trans-cooler-my-detailed-write-up.15508/

Mishimoto directions:  https://www.mishimoto.com/mwdownloads/download/link/id/1403

Mishimoto 7.3L 37 Row Transmission Cooler 99-03: https://www.riffraffdiesel.com/mishimoto-7-3l-37-row-transmission-cooler-99-03/

Mishimoto Transmission Cooler for 6.0L Trucks: https://www.riffraffdiesel.com/mishimoto-6-0l-37-row-transmission-cooler/

 

*photo credit: Mishimoto

***Disclaimer: The information provided on this blog is for informational purposes only. We share our knowledge and experience, but we are not liable for any damages, injuries, or losses that may occur as a result of using this information. Situations are rarely cut and dry in the automotive world. Your situation will likely be somewhat different than what we describe here.  Use your best judgment and always consult a qualified professional for automotive repairs and modifications. Your safety is your responsibility.