PROJECT WORK TRUCK
Rebuilding a Ford 4R100 transmission for towing and hauling
he 4R100 transmission in Vincent Uriah's 2003 Ford F-350 work truck has been a hard worker for most of its long life and despite upgrading to a triple-disc torque converter and modified valve body some time ago, the high-mileage factory clutches could not handle the heavy hauling any longer.
TUnfortunately for Uriah, the heavy towing of earth-moving equipment for his concrete business, combined with the additional power the 7.3L Power Stroke engine is now making, did not bode well for the factory clutches and the transmission started to slip under load. Upon teardown, Swamp’s transmission specialist Dan Morin determined that the forward clutch pack suffered a catastrophic failure with the clutches completely self-destructing. The design and operation of the 4R100 transmission applies the clutch packs in a cumulative arrangement, meaning that the clutch packs apply and add to the previous stage to make the transmission shift gears. So once the forward clutch pack (which is engaged in all forward gears) started to slip, the clutches simply burnt themselves up, leaving the truck stranded.
Rather than rebuild the transmission to factory specs at the dealer or a local transmission shop, Uriah chose to trust the expert diesel specialists at Swamp’s Diesel Performance in Lavergne, Tennessee. They suggested upgrading the 4R100 with an Xtreme rebuild kit from Suncoast Converters as well as their four-disc coast clutch drum and 2-3 shift valve. In addi- tion to using higher quality Raybestos clutches and Kolene-coated steels that handle high heat better, the Suncoast kit features machined components to allow more clutches and steels to be used in each pack for more holding power and less heat buildup. The Xtreme rebuild kit and upgrade parts will work well with the valve body modifications Morin performed previously, allowing the transmission to work well with heavy loads and engines in the 450-550 horsepower range.
Not only does the Suncoast Xtreme rebuild kit use better quality clutches and steels in
each clutch pack, it also uses additional clutches in the direct, forward, intermediate, coast and overdrive clutch packs to increase the holding power of the transmission. To fit more clutches, Suncoast supplies machined apply plates in the direct, forward and overdrive clutch packs. In the intermediate clutch pack, additional room for more clutches is accomplished by Suncoast including thinner steels with the rebuild kit. To fit more clutches into the coast clutch drum, Suncoast machined a new retaining groove into the drum that allows the number of clutches to be doubled from two to four. As you would guess, there’s a purpose to squeezing additional clutch discs into the transmission—it provides additional power holding capability by spreading the load across more surface area.
After towing the Ford F-350 up to the Swamp's shop, Uriah left it there for a three-day turnaround that included part of a day to pull, disassemble and clean the transmission case, a day to rebuild the transmission with the Suncoast parts, and part of the third day to reinstall and road test the truck and optimize the tuning for the new transmission capabilities. Of course, our camera slowed down the process, and the guys at Swamp’s could have had the truck done in two days without our interference for photography during the assembly. To help facilitate the quick turnaround and get Uriah’s work truck back on the road and making money quickly, the builders opted to use a Suncoast billet multi-disc torque converter rather than sending out the converter that was installed earlier to be serviced to remove the contamination from the transmission’s destroyed forward clutch pack.
Thanks to a Suncoast Xtreme rebuild kit, billet torque converter and the guys at Swamp’s Diesel Performance, Uriah’s 4R100 transmission is ready to tackle any load.