Only two times mine has let me down. Once the factory installed Jacobs vacuum pump pulley siezed, shredded the serpentine belt, snapped the tensioner pulley and sent it into the back of the radiator, and broke the fan shroud. I ditched the Jacobs after the second failure in 71k miles, and now have a PacBrake.
The other time my #4 injector line split at 4:30 a. m. leaving on a 2,000 mile trip. It sprayed fuel over everything. I drove it home anyway (about 18 miles), picked up a line at the Cummins dealer, and had it back up and running by 10 a. m. It took awhile to splice the injector harness back together... 20,000+ fuel pressure does amazing things! I now carry a full set of high pressure lines with me.
I've been in numerous situations that should have left me stranded, but I've got out of every one of them. I've broken through 8" thick ice into a shallow pond, slid off the road down an embankment in a blizzard into a creek, and been buried up to the front bumper in mud. This truck has got me out unassisted (well, other than a few prayers) in every case.
I'm glad I bought a ram.
--Eric