Simple Transmission Upgrades For Towing And Hauling
When operating behind a factory 7.3L Power Stroke engine making around 250 horsepower, the 4R100 is a great transmission and will generally perform well for many years and many miles even when towing heavy loads. But when performance modifications ramp up the horsepower and torque, most stock transmissions reach their limits, including the 4R100. Rather than wait for problems to develop, it’s better to be proactive and upgrade the transmission before really turning up the wick on your Power Stroke’s performance.
That’s the route that concrete contractor Vincent Uriah of Summerville, Georgia, decided to take with his 125,000-mile 2003 Ford F-350. He turned to the experts at Swamp’s Diesel Performance in LaVergne, Tennessee, to install one of their performance modified valve bodies, modified TransGo valve body plate, Precision Industries torque converter and Mag-Hytec transmission pan to hold an additional 7.6 quarts of Schaeffer’s ALL-TRANS Supreme fully synthetic transmission fluid.
Rather than a full transmission build, the crew at Swamp’s will simply be upgrading the transmission since it has relatively low miles, still shifts firmly, and the fluid did not show any signs of abuse or excessive wear. If the transmission is already slipping and has worn or damaged clutches it needs a full rebuild, not just an upgrade.
In a transmission like the 4R100, the valve body is the brain of the transmission and controls its operation, including line pressures, gear selection and shift firmness. By modifying the valve body and installing the modified TransGo valve body plate, the team at Swamp’s is able to not only extend the life of the transmission, but also allow it to handle the additional power that Uriah’s F-350 is now making as well as more power to come in the future.
With overdrive transmissions and lock-up torque converters in automatic transmissions for diesel applications, the torque converter has an incredible load put on it, especially with modified engines. The factory converters are usually okay for stock power levels, but will not hold up well to additional power. Their weak single-clutch assemblies and stamped steel construction are just not strong enough to handle high-torque loads especially when heavy towing is involved. The option for this truck is a Precision Industries heavy-duty torque converter that can handle the power and towing demands.
The Stallion torque converter from Precision features a one-piece machined billet cover for added strength and rigidity to make a strong foundation for the converter. The internals consist of a multi-disc clutch that has more than 3.5-times the surface area of the factory clutch for solid engagement that will not slip even under heavy loads with high-power engines. The new converter also includes a five-year warranty and will generally provide fuel mileage improvements due to better fluid coupling as well as better acceleration thanks to increased torque multiplication.
Installing the modified valve body and valve body plate can be done with the transmission in the truck as can swapping out the pan, but to replace the torque converter the transmission must be removed from the truck. We followed along as Dan Morin performed the installation on Uriah’s F-350 at the Swamp’s shop. Fortunately for us, he used one of the shop’s drive-on four-post lifts so we were easily able to be under the truck with him to capture the following photos and bring the highlights of the installation to you.
Morin had the transmission out of the truck in well under an hour, then he cleaned up the case, swapped out the converter and reinstalled it back in the truck. Before he reinstalled the transmission, he poured out the used fluid from the old torque converter directly onto his transmission bench to analyze the fluid. There was very little metal found suspended in the fluid and it did not smell burnt, verifying his prediction that the 125,000-mile transmission has been well maintained and is in reasonable health.
Once the transmission was back in the truck he drained the rest of the old fluid and removed the pan and filter. Then he removed the old valve body and replaced it with a valve body that he rebuilt and modified earlier in the day, sandwiching the modified TransGo plate between the transmission and the valve body.
After the valve body, he installed the new filter that was supplied by Mag-Hytec. When removing the old filter and installing the new one, be sure that the old seal comes out and if it’s stuck, remove it very carefully so that you do not damage the bore and create an internal leak in the transmission that would hurt performance and potentially damage the transmission. Before installing the pan, Morin chased the threads in the transmission case to clear any road grime that had built up in the upper portion of the threaded mounting holes.
Once the pan is buttoned up and the truck is lowered back down to ground level, he filled the transmission with 16 quarts of Schaeffer’s ALL-TRANS Supreme fluid before starting the truck and topping it off. The total transmission capacity will be close to 24 quarts (or six gallons) of fluid with the deep pan so be sure to have enough fluid on hand to complete the installation. A word of caution in filling the transmission, though, do not fill all of the fluid before starting the truck as it will overflow and leave you with a big mess on the floor.
Advanced DIY diesel enthusiasts can handle an upgrade like this themselves in their garage or driveway. Unfortunately, working with the truck (properly supported) on jack stands will be more difficult than using a lift in a professional shop, but it’s doable, it will just take more time and effort. You may need a friend to bar over the engine so that you can access all the torque converter bolts to unbolt it from the flexplate before removing the transmission and again to install the new bolts securing the Precision converter to the flexplate.
With the Swamp’s modified valve body installed in the transmission, the shifts are crisper but not overly harsh and the torque converter lockup is solid. We expect fuel mileage to be slightly improved, but the main reason for the upgrade was to strengthen the 4R100 transmission to hold up to increased power, especially when towing heavy loads. In last month’s issue, the crew at Swamp’s gave the truck more power with intake, exhaust and tuning upgrades and they’re planning to give it even more power in the future. Stay tuned and follow along with the monthly upgrades on the old work truck. DW
14718 Arminta St.
Van Nuys, CA 91402
120 Independence Dr.
Whiteville, TN 38075
102 Barton St.
St. Louis, MO 63104
Swamp’s Diesel Performance
304 Sandhill Road
LaVergne, TN 37086
2621 Merced Ave.
El Monte, CA 91733