Regardless of what other believe, the Automatic transmission that Dodge has selected for use in the Dodge Ram 2500 and 3500 series trucks is under-rated for the task at hand. The torque converter is the weakest link, the stall speed is to high and it is not capable of handling the loads that many expect and require for a diesel powered pickup. The trany itself is not bad, it has been used by Dodge for almost 40 years in one form or another. From what I can see, low oil pressure and lack of oil circulation while in park are the two major flaws. These then of themselves are not that bad, but coupled with the troubled torque converter and all the heat it produces, early failures are not so uncommon. The torque converter just does not have the grip needed to do the job many buy a heavy duty truck to perform. Towing large and heavy loads with a diesel powered truck, puts alot of strain on the torque converter. It has to have enough friction area to hold the torque produced by the diesel when the torque converter locks up, these clutches are two small on the stock Dodge automatic transmission. As the load increases to the point of over-powering the amount of grip the TC has, slippage is produced. This produces very high temperatures at it's source, which only helps to further weaken the ability to hold torque. The end result is damage to the clutch area and damage to the entire transmission from heat and it's associated effects.
I don't think there are any cheap and quick fixes. You only waste your money by purchasing shift kits, pressure-locs, valve bodies, etc. These may work great when combined with an overall plan to up-grade the transmission, but do little when used separately in hopes of a quick fix or band-aid. I think the number one and most important trouble spot to tackle first should be the torque converter. It is seldom on that "first fix" list, because of it's expense and hard to reach area. If this is not possible, then I would refrain from spending anything till it fails and then fix it right. There are several good options for replacements available, most of these address the entire transmission as a whole, and will provide the user with many miles of increased performance and durability. Hopefully Dodge will offer a newer and more capable transmission soon, one that may even be fitted into the older trucks, till then save your money for the forthcoming expense.