So i have not had the trans fluid and filter chang's on my truck and i was thinking about doing it. So i have called around to a few shops and got a quote to have it done but one shop i called the guy told me you are not really supported to change the fluid unless you have too. Is this true or is this guy just retarded? Because no other shop told be this and another shop told me i should go ahead and change the internal filter also while I'm at it. Truck has 160k on it. Not many for a duramax and an allison but i still think it should be changed. At least the fluid and the spin on filter.