From a current owners perspective and having owned two trucks I have to say I've been very pleased with my 5.9 diesel. I had a 2002 2wd and it pulled like a freight train while getting fairly decent fuel mileage. My second and current truck is a 4wd 2500 and it too has a lot of power but falls short on the fuel mileage. The 3.73s combined with the additional emissions probably probably contributes to that.

I have 213k on the truck now and it hasn't missed a beat power or reliability wise. As far as the transmissions I can't speak to the manuals but as far as the automatic no problems. The key to making the autos live is maintenance. As long as the trans is serviced on a regular basis it will live a long life.

If I were in the market I would be looking at a 2005 or 2006 CTD.