No one unit turn is all there trucks....the trucks were put in strategic reserve fleet, then auctioned off. Vehicles for the most get dumped out once they become economically not repairable or outdated...that's why some many M1114's are being scrapped. Others like MRAP's just have no use once the war was over...so scrap or 1033 program.
but it's all based on how many units are active, the more downsizing, the more scrap. Lather, rinse...repeat.
this way on the next war and build up, all the defense contractors can make there profits...