I'm pretty sure GM came out with a updated intermediate shaft that doesn't use grease. The issue with the intermediate shaft is that the grease eventually pushes out where the two shafts slide into each other. I think the newer ones have some type of rubber bushing in it.

Get the dorman shaft. Worked for me

is the truck stock or has mods ? I had a 05 for several years, had mods and edge tuner, but got about 11, when I got my 08 same deal had mods and had been tuned...got terrible mileage, had duramaxtuner do a swap out ECM and truck is great now...so sometimes just a bad tune will kill the mileage..

The one I had I had to put a new front end under the truck at 65k & again at 130K. About 131K the wiring harness went out.

The 2004 1/2 they made a change for emissions and caused all kinds of problems. As soon as I put a trailer behind the truck and temps were in the 90's the fan clutch would say engaged all most the whole time and would only get around 8 mpg. If the temps were cooler and the fan clutch would not stay engaged the mileage would go up to 11-13

If the dealer changed the steering shaft he put parts in that were not fixed of the issue. The fix came years later and the Dorman parts are the ones to get.

There is a plastic bushing under the dash that wears and allows the steering shaft to rattle, it can be replaced or squeezes slightly with a hose clamp. I put a clamp on mine more than 50k miles ago and issue has not returned. Check out dieselplace for a how to

The turbo inlet from the air intake is horrendous on the 04.5 and 05 trucks. Upgrading that to an 06 style elbow will free up torque, economy, and keep the engine running cooler while towing. Here is a little reading on the problem and solution: http://killerbeeperformance.com/indu...tion-overhaul/ . My 05 would average 12-13 hauling about 9K in the winter.

Pretty sure that's what it is. I actually read about it, and did the hose clamp trick the other night when I was back over to his house. Drove around the block, and no noise, so I think its fixed. thank you.

Those years with the 5 speed trans werent great on hwy fuel economy unless you stayed at 65. At 65 it shouldve been just under 2,000 RPM's and the higher you go over that the worse the mileage gets.

If it was getting 8 and its stock and you werent running 75+, then yes it needs some maintenance done.

My 2004 lb7 truck gets 8-9 no matter whats hooked on it, motorcycle trailer, boat, 38ft flat bed. But I also run 75-80 so I don't expect it to be good.

Rattle under the dash is the plastic bearing under the column, while the ISS is out make sure its free and replace as needed.