Well, the military didn't spec out an overdrive of any sorts. I did have a 1984 K10 that went 400,00 miles and it did have a 6.2 and 4 spd auto with OD and 22 MPG was the norm. 80 MPH was realistiic as well. Unable?????
I don't think the transmission issue was the cause of them crumbling either but I've been wrong before.
What did the body look like?
I remember my father and his contemporaries talking about 'Japanese junk'. It may have started out that way but they got better (reminds me of current the talk of Chinese junk). It is not that American engineers and assembly workers cannot design and produce quality cars (or anything else for that matter) it is my belief that they are not allowed to do so by short sighted management.
I love my M1009. I don't like that it does not have a four speed transmission (my understanding is that the four speed was fairly new and not as stable as the TH400). I hate the crappy tailgate/back window design. I think the wheel well lip that catches and holds salt and moisture was not well thought out. I still love it though.
I have a ford taurus at the moment with over 235K on it and outside of normal maintenance items all that has been replaced (knock on wood) are the ball joints, a cylinder coil and a broken wire leading to that drivers door.
I am sure you have as many stories as I of friends and neighbors who have been so burned by the American car manufacturers that they have sworn never to by another American made car again. I do believe that without stiff foreign competition our good American brothers in the highest levels of management would still be selling us crap. As far as I am concerned there is no reason (other than choice) why any American car maker was/is not producing the best automobiles the world had/has ever seen. I would like to believe that the global demand for such well engineered, well built and long lasting automobiles would keep the production lines struggling to keep up with demand. I wonder why GM went bankrupt instead.