There is an old saying: "never throw away your old rag until you have a new one". And ford has done that repeatedly. The F series trucks with the 7.3L Power stroke engine by Navistar (international harvester) was there greatest engine and out performed GM and Dodge by far. They replaced that engine with a Ford designed 6.4L for there Super Duty trucks, they also replaced the tried and true 4R100 & 6R140 5 speed tow/haul transmission designed by for the 5R110W 6 speed automatic tow/haul transmission designed by Ford. In the last 10 years, Ford trucks have gone down in both performance and reliability. Almost every military truck that is manufactured by Oshkosh, Stewart & Stevenson, AM General, FPI (General Dynamics) has either a CAT, Cummins engine or a Navistar Powerstroke engine. Now Chevrolet uses Duramax (Isuzu) and Allison transmissions and for the last few years have remained on top of the heavy duty truck podium.