I had a 2004 2500HD crew cab shortbox and pulled a 36.5 Landmark 5er. It did much better after adding the Ride-rite air bag package which leveled it up. Handled much better. The LLY can pull it if you have fixed the LLY overheating problem. More on this on the Duramax forum if you look up LLY overheating issues. I added an AFE turbo inlet manifold, 3" Banks inlet tube and an Earl's trans oil cooler. Read the Allison owners manual on transmission operation. Its online somewhere if you didn't get one. I can understand keeping your truck if its paid for.
