I bought a 2010 GMC 1500 sierra 5.3 that was to have 342 gears but ended up with 308. I pull a 6000 lb travel trailer. Need advise on changing gears out to 373 or 342. Anyone done this or have advice as to if I should proceed? What cost am I looking at and how much does gas mileage drops. I do have trailer package and tow with tow in while pulling my trailers (travel trailer/bass boat) not at the same time.
Charlie