The Duramatch 2 does have the problem, as a previous reply described, they do work extremely hot in certain applications and overheat. Having the oil cooler under the radiator also compounds the problem by also transfering the heat to the engine which will also overheat. The inching set up can be very erratic and dificult to get a smooth operation and its also very jerkey when changing to second speed. These can all be smoothed out by changing the parameters, but give it a week or so and they all come back.
But the most worrying problem try sitting on one of these, dont touch any controls except selection of a direction, the truck will then drive off in the opposite of what has been selected until the pedals are pressed, give it a go amazing.
having said that I am not aware of any internal failures that has required a transmission repair.