PROJECT WORK TRUCK

Re­build­ing a Ford 4R100 trans­mis­sion for tow­ing and haul­ing

Ultimate Diesel Builder's Guide - - Contents -

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.

Vin­cent Uriah re­lies on his 2003 Ford F-350 to haul heavy equip­ment to and from job­sites so when the trans­mis­sion gave him prob­lems he needed help to get it back on the road quickly.

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.

1 Strip­ping down your au­to­matic trans­mis­sion and bring­ing the in­side out is not some­thing most DIY week­end wrenches can han­dle. The task is best left to ex­perts who have the tools and know the tricks to build your trans right. With a team like the one at

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