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Ford Super Duty 4R100 Transmission - The Wood Way

Rebuilding the Super Duty 4R100 for severe use

Robin StoverPhotographer, Writer

When it comes to heavy hauling, most people would agree that the Ford Super Duty platform is probably the most favored of the bunch. Since its inception, annual sales have been staggering at over 200,000 per year. This equates to well over a million Ford Super Duty trucks in service today. The bulk of these were equipped with the 7.3L Power Stroke diesel option, and the great majority of these came with the time-tested four-speed automatic known as the E40D or 4R100. This transmission was suitable for stock power levels (and end users who do things by the book), however, once overloaded or exposed to increased torque loads, both the E40D and 4R100 quickly showed signs of weakness.

That's why we did a little investigative work to see how these transmissions could be configured to perform reliably under even the most demanding conditions. Our search led us to John Wood Automotive of Holtville, California. Wood started building Ford transmissions in 1983 and prides himself with a reputation for utmost attention to detail and customer satisfaction. Wood operates his business on the principle of quality before quantity, which with only one assistant requires he take on only one transmission rebuild per day. This methodology pays off, as most of Wood's patrons are referred by word of mouth. Diesel drag racing, sled pulling, sand-dune running, and heavy towing are the primary lifestyles of Wood's customers.

Wood has an intensive educational rebuild program that's set up to teach Super Duty owners all the ins and outs of their transmission in one full eight-hour work day. Some customers take notes while others take a rain check and visit the nearby Glamis OHV area, but everybody leaves happy knowing they have the most efficient, reliable, and robust E40D or 4R100 money can buy.

Each and every transmission Wood rebuilds also receives a brand-new factory Ford Super Duty radiator. This is always necessary because, once contaminated with clutch material, it's almost impossible to get the same efficiency from the built-in transmission cooler. In the case of '99 trucks, Ford didn't include a built-in transmission cooler with the radiator. This is part of the reason why they had that silly bypass circuit with the check valve shown earlier. In '00-and-later Ford Super Duty trucks, they improved this design and included a separate circuit for ATF temperature regulation at the bottom of each radiator. This design helps bring the ATF up to normal operating temperature at initial start-up. It also helps cool the ATF under extreme conditions.

Another service John Wood offers his customers is custom ECU tuning via SCT's performance interface and computer software. We had him tune our donor's truck for improved power and higher top speed, as well as speedometer calibration settings for 40-inch tires. In addition, this software can take out power for improved reliability in fleet trucks or set a speed governor for teenage drivers. Our donor really liked the performance gains this retune provided for his truck. In fact, it worked so well, he decided to get rid of the plug-in tuner that caused his troubles in the first place. After over 1 1/2 years and nearly 29,000 miles on the Wood-prepped transmission, our donor is very happy and still enjoying his Ford Super Duty's newfound reliability and performance. The cost of this rebuild was not inexpensive, but considering what you get for the money, we feel it's one of the best programs available for the 7.3L Ford Super Duty owner.

For those of you who don't need to spend a fortune on transmission performance like our donor did, but still want to tow reliably with up to 350 hp, Wood has an option for you too. This year, he came out with a new rebuild program where he guarantees his work for 75,000 miles or three years, whichever comes first. This program was designed for the average Joe who simply has an intake, exhaust system, and/or a programmer. The price for the Towmaster rebuild is $3,600-not bad, considering the average dealership rebuild is around $3,800.