2007 Chevrolet 3500 for towing

I’m buying a dual rear wheel diesel 3500 crew cab long bed with 140,000 miles to tow a 30 to 35 ft 5th wheel RV. This is an early 2007 “classic body” What potential problem areas should I be looking for, and what should I plan on doing to be proactive in preventative maintenance?

Ok, so you are buying an 11 year old big truck. Was this driven by a drugstore cowboy or a working guy or a camper guy? With 140K, the drugstore cowboy truck should have nice smelling trans fluid and diff fluid, and engine oil. And the miles likely won’t be all that hard. But this wold be a fairly rare thing 'cause 3500 duallys are usually rode hard! And 140K on a tow rig is a bit high.

Does it have a 5th wheel hitch or a gooseneck ball i the bed? Does it show lots of wear? Is the 2 inch receiver shiny and polished? Proof of working HARD.

Does the truck have receipts for transmission oil and filter changes? Axle fluid changes? Regular oil changes? If a dealer is selling this, it won’t and that is a risk, in my book.

If you’ve already made up your mind, a complete fluid change of everything (brake and power steering fluid, too) is mandatory as well as coolant. I prefer synthetics for oil and gear-oil.

Check the brake hard-lines as they tend to rust very badly. Same for fuel injection hard lines. Full brake check, including axle seals, bearings and grease seals. Replace the fuel pump, just do it, it is due and it will strand you if it fails. Check coolers and lines for corrosion.

If it is a diesel, I don’t know much about any special maintenance but there are DuraMax diesel forums as well as RVing forums that can help. Good Luck