At the company I spent my first 6 years with, we had all fords. I bet we had 20-30 of the 2000 - 2004 year model fords. All diesels. Not one single truck, not one, made it to 100,000 miles without losing the rear end, transmission, or headgaskets, or a combination of all three. My truck made it to 98,000 miles, and the head gaskets blew. Some went through three rear ends, some had multiple trannys, before 100,000 miles. These were all F-350-550 trucks. Most were the F-550's. Had a flat bed on them with tool boxes, generator, air compressor, threaders, and a host of tools. Never pulled anything more than a bumper pull trailer. Except a few like mine that stayed hooked up to a gooseneck. We had to have about 10 spare trucks just to keep everyone working. It was a nightmare. Finally went to the chevy gas burner one tons. We started getting 150k miles out of them, and never having to touch them. Literally, several went this long without ever having any issues, other than a/c switch or something minor going out. Never put a motor, tranny, or rearend in the first one. By the time I left, we had close to 60 of those chevy one tons, all gas, running around. Now we would have one every now and then give us issues, but never a motor or tranny or rear end. So, that's what we have stuck with.
Started off with a few dodge one tons in my company now. And they were better than the fords, but couldnt touch these chevys. Running all chevy one tons now. Got about 20 gas burners, and 6 duramax's.
Now, we do have two ford gas burner half ton 4x4s, and one gas burner 3/4 ton. I havent had any problems out of them. I like the ford half tons crew cabs over the chevy, for work.
I will never give up my duramax though...