7.3 Transmission Cooler Upgrade Kit

A transmission is not something that most truck owners think about… until one fails, that is. The most common cause of failure in an automatic transmission is not age; it’s excessive heat. Towing, especially of heavy loads while in overdrive, can cause this heat. Sure, regular tranny fluid changes and towing in third can extend the life of the automatic in your Ford Super Duty, but a properly sized transmission oil cooler is the most important part of the cool-running automatic transmission equation.

Owners of ’99-’03 Ford Super Duty trucks know that the 7.3L Power Stroke diesel engine is a good engine. Unfortunately, the 4R100 automatic could be a little tougher and these trucks are also plagued with factory tranny coolers that run a little on the small side. The ’99 to ’03 Fords with the 7.3 are fine for daily driving. However, the OEM cooler can be over-taxed while towing heavy loads and the heat that results can mean issues with the auto trans. Not to worry, there’s a solution, a 7.3 transmission cooler upgrade kit and it involves some top-quality OEM parts.

1 The grille is best removed to make your installation easier.

2 The lower air dam and the power steering cooler are removed to install the transmission oil cooler. The power steering cooler can just be hung to the side while making the trans cooler upgrade.

John Ferguson at Domestic Diesel Service in Corona, California, offered to show us the solution. He’s a Certified ASE Master Mechanic and started in Ford’s service department in 1996. He’s familiar with the Ford diesel lineup and the parts they use. His solution is to swap out the smallish 7.3L transmission cooler for one of the larger units that were standard in the Ford 6.0L Power Stroke-equipped trucks. A 7.3 to Ford 6.0 transmission cooler kit, so to say. That’s right, a 6.0 trans cooler for the 7.3.

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Now this is not a direct bolt-in, but it’s close to it. The fact is, the later model coolers will fit behind the grille of your 7.3-equipped truck, with a few minor modifications. The first of these modifications is the cutting and splicing of the rubber lines that run from your transmission to the original trans cooler. These lines are 3/8-inch diameter and the new cooler takes ½-inch lines. Domestic Diesel offers a small parts kit with adaptor fittings to splice the two line sizes. (The kit also includes other required small parts). The fact that the cooler takes a larger line is not a problem; bigger is better, so there’s no issue with restriction of flow. In addition, the new cooler will have a slotted lower mount that will require either a fender washer over the two lower mounting bolts, or the use of the OEM 6.0 rig rubber bushings. Fender washers are in the small parts kit and work great. Also, they won’t deteriorate over time like the rubber will.

3 The stock transmission cooler for ’99-’03 Fords with the 7.3L Power Stroke is smallish. Some would say it would make a nice upgrade for the power steering cooler, but the brackets make that problematic. Notice that the cooler has hard-line fittings. These lines run back to the transmission, and have a rubber center section that’s cut and spliced into.

4 Here you can see the coolers Ford selected for the 6.0L-equipped trucks (left and center) and the stock cooler for the 7.3L on the right. The smaller of the two late model coolers is a 26-row unit that has more than 124-percent more surface area than the original cooler. The larger cooler is a little taller, has 31 rows and a whopping 172-percent more surface area than the original cooler. More surface area means more heat dissipation and a cooler- running transmission.

5 This is the open lower mounting tab on the two 6.0-style coolers. A simple fender washer on the stock bolt will ensure this mount doesn’t come loose.

6 The transmission lines on the 7.3L trucks have crimped hard lines on each end, and a 3/8-inch flex section in the middle. These lines are cut and 3/8- to ½-inch adaptor fittings are installed to mate with the new cooler input fitting size. The new cooler has standard push-on line fittings.

7 Here you see one of the 26-row coolers being installed in our test truck. This cooler has more cooling capacity than two of the stock coolers and is ideal for all but the most intensive heavy towing tasks.

The lower splash cover under the bumper must be removed and the installation should also be done with the grille off. This is not hard to do, as the factory makes these parts easy to take off for service and assembly reasons. Some will tell you to remove the front bumper, but with a swivel attachment you can get around this task and save time. From start to finish, this upgrade should take you from four to six hours, depending on interruptions and your comfort level.

Ford offers two different transmission coolers for the 6.0 powerstroke. The smaller one is good for all but the most strenuous towing needs. The larger cooler can be used too, if you want to go for the ultimate cooling package for your transmission. Of course, being larger, it’s a little more work to get in, but it does fit without any major modifications.

8 The new ½-inch cooler lines are attached to the new transmission cooler with simple hose clamps.

9 The stock power steering cooler is unbolted and hung out of the way for the upgrade and then fits in the stock location without any issues after the upgrade.

10 When upgrading our transmission cooler, we took the opportunity to drain the transmission, change the filter and replace the old fluid with new.

“A larger transmission cooler is sure to drop your running trans temps over the stock unit.”

11 When replacing your transmission fluid, only use premium, top-shelf fluid. The cost savings of cheap transmission fluid is not worth the risk. Domestic Diesel Service uses only OEM transmission fluid, just like the dealer.

We’ve seen reports of a 30-degree-average trans temp reduction when running unloaded. When towing, some have claimed as much as 60-plus degrees in temperature reduction over the stock trans cooler. These are subjective numbers and your results may vary. One thing’s for sure: a larger transmission cooler is sure to drop your running trans temps over the stock unit. DW

CONTACT:

Domestic Diesel Service
909-627-0500
www.domesticdieselshop.com

FREQUENTLY ASKED QUESTIONS

What is an easier method for installing a transmission cooler upgrade on a 2003 F350 7.3 SRW?

How to Easily Install a Transmission Cooler Upgrade on a 2003 F350 7.3 SRW

Upgrading the transmission cooler on your 2003 F350 7.3 SRW doesn’t have to be daunting. Here’s a straightforward approach that simplifies the process.

Preparation

Before you start the installation, gather the necessary tools and parts: a new transmission cooler, fittings, and quality transmission fluid. Ensure your workspace is safe and the truck is securely lifted if needed.

Step-by-Step Installation

Initial Disassembly
Begin by removing the front components for better access. Detach the front bumper, grille, and the upper shroud that covers the top of the AC condenser. This provides clear visibility and space to work.
Detach Existing Components
Unbolt the hood latch and remove the top brackets of the AC condenser to tilt it forward slightly. Begin unfastening the stock cooler by taking out its bolts and disconnecting the lines from underneath the truck.
Remove the Existing Cooler
With the condenser tilted forward, carefully rotate and slide out the old transmission cooler. Cutting off the ends of the lines where they connect can make this process smoother.
Prepare the New Cooler
Attach the necessary fittings and grommets to the new cooler. Position it on top of the engine temporarily as you guide the new lines down between the intercooler and the condenser.
Install the New Cooler
Position the new cooler with one hand while gently pulling the lines through from the front with the other. Ensure the lines are not kinked and proceed to secure them as needed.
Reassembly
Bolt the new cooler into place and realign the AC condenser brackets. Reattach the hood latch, followed by the grille, bumper, and upper shroud.

Final Steps

After installation, fill the transmission with additional fluid if necessary, as the upgraded cooler may have a higher capacity. Check the fluid level to make sure everything is set correctly, and you’re ready to go.

By following these simplified steps, you’ll enhance your truck’s towing capability and ensure better performance, especially in demanding driving conditions. Enjoy your ride, now cooler and more efficient!

What additional modifications can improve the towing and driving experience of a 7.3L diesel truck?

Enhancing Your 7.3L Diesel Truck for a Better Towing and Driving Experience

If you’re looking to elevate your 7.3L diesel truck’s towing and driving performance, consider these game-changing modifications. Each of these improvements not only enhances vehicle functionality but also boosts your overall experience behind the wheel.

1. Upgrade Your Turbo Wheel

One effective modification is replacing the stock turbo wheel with a high-performance aftermarket option. This upgrade can increase the boost pressure, making it essential for mitigating turbo surge, a common issue during heavy towing. It’s a safe enhancement for both stock and modified trucks, providing smoother power delivery.

2. Install a Modified Valve Body

Enhancing transmission performance is crucial, and switching to a custom-modified valve body is an excellent start. These are designed based on your unique needs, ensuring improved shifting capability. Installation involves unbolting the original valve body and securing the new one. Remember to refill the transmission fluid afterward for optimal operation.

DIY Tip:Use an inch-pound torque wrench for accurate installation.

3. Mirror Upgrade Kit

Another valuable upgrade is installing larger, tow-friendly mirrors designed for models post-2008. These mirrors significantly enhance rear visibility, making towing safer and more manageable. They also add a modern aesthetic touch to your truck.

Key Considerations

Always consult with professionals if you’re unsure about installation processes.
Consider reliability and quality when selecting modifications to ensure long-term benefits.
Regular maintenance post-modification can help sustain these improvements.

By implementing these modifications, you’ll discover a marked improvement in your truck’s handling and towing capabilities, making road trips and heavy hauls more efficient and enjoyable.

How did changing the transmission fluid and installing a new cooler affect the truck’s performance and temperature?

“We’ve seen reports of a 30-degree-average trans temp reduction when running unloaded. When towing, some have claimed as much as 60-plus degrees in temperature reduction over the stock trans cooler. These are subjective numbers and your results may vary. One thing’s for sure: a larger transmission cooler is sure to drop your running trans temps over the stock unit.

In practical terms, users have noted significant improvements not just in temperature but also in performance. For instance, during normal driving conditions, some have observed temperatures dropping from around 180 degrees to 120 degrees in cooler weather.

When it comes to towing, the difference is even more pronounced. A truck pulling approximately 9,000 pounds showed temperatures that didn’t exceed 130 degrees—a testament to the cooler’s efficiency.

Beyond just temperature, the new setup often results in a smoother ride. Many drivers report the transmission shifts more smoothly and responsively, eliminating the harsh jerks and hard shifts that can occur with a stock cooler. Overall, this upgrade doesn’t just keep your transmission cooler; it also enhances the driving experience by improving pulling power and responsiveness.”

What were the initial transmission temperature issues experienced with a 2003 F350 7.3 SRW while towing?

For instance, transmission temperatures in a 2003 F350 7.3 SRW would typically run around 200 degrees while towing. However, these temps could climb to the 220-230 degree range on hills or in stop-and-go traffic, clearly signaling a problem. In contrast, normal driving without a load would see a more stable 185 degrees, even in cooler weather conditions.

The ’99 to ’03 Fords with the 7.3 are fine for daily driving. However, the OEM cooler can be over-taxed while towing heavy loads, and the heat that results can mean issues with the auto trans. Not to worry, there’s a solution, a 7.3 transmission cooler upgrade kit and it involves some top-quality OEM parts.

By addressing this excessive heat issue with an upgraded cooler, you can keep your transmission running smoothly and reliably, even under the heavy demands of towing.

What were the circumstances under which the temperature increased?

The temperature rose when towing was done on inclines or during stop-and-go traffic situations.

How did the transmission behave under different driving conditions?

During normal driving without a load, the transmission maintained a temperature around 185 degrees, even when the external temperature was as low as 40 degrees.

What were the actual transmission temperature readings during towing?

The transmission temperatures during towing typically reached around 200 degrees, but increased to 220-230 degrees on hills or in stop-and-go traffic.