We have an 02 3500 dually with 5.9 eng.stock(65000mi.) with auto trans. pulling a 12000# 5th wheel don't seem to have any trouble pulling it. Can I expect the trans to hold up if I leave the truck stock? Thanks Jerry

 

should be okay, as long as proper maintence is performed, but unexpected things can always happen, you should really put a trans temp gauge and fuel pressure gauge in that truck for piece of mind, the trans temp so you dont over heat the fluid, and fuel press to watch the lift pump fuel pressure which are known to go out and will destroy the injection pump in as little as a few miles

 

x2 as what dodgetrucker said