Ford 4R100 automatic transmissions frequently fail around 100,000 miles. The main reason these transmssions fail prematurely is that the torque converters are not well built from the factory. Slippage causes excessive heat which leads to failure. The design of the transmission is, however, superior and capable of greater strength and reliability than Dodge transmissions. Behind the torque of a Cummins, you'd want a shift kit and a billet multi-disk torque converter at the least. Check with BTS about transmission options and what the Ford variety can handle.