As much as I loved my 00 Ram, it started showing its age last year before I got rid of it. If you get a 5.9 Magnum, get rid of the "beer keg" manifold. Mine started leaking before I got rid of it. As Berto said, ball joints and tie rods will go bad (like every other truck), but a little faster than the others. Switch to Moog ball joints/tie rods and fix it right away. Never had any issue with the transmission, other than a $12 sensor. With a Dana 44 front and a 9.25" rear, the axles are usually solid. Again, with over 100K, it may toss a bearing or 2 in the rear end like mine did.
I wish I still had my old Ram as a knock around truck. I never had any major issues with it, besides 10 MPG, but it's a truck.