Drove my Dad's 1500 this past week. Steers SOOOOO easy! I can drive the truck with one finger, even at slow speeds and tight turns. My truck takes some work to turn, ESPECIALLY at low speeds and in tight spaces. He has stock tires and mine are 285/75/16's. Is it something more than the tire size? I feel sometimes that I have NO power steering!

There is a lot less weight sitting on the frontend of a gasser than your Duramax. Maybe that's it?

Is his a 2wd ? If so... I had a 2001 1500 and you could steer it by breathing on it.

2wd/4wd doesnt make a difference, I think the pumps or steering components are just lighter weight. I had an 02 avalanche, could steer with my finger hair. My 2500 is pretty tough, takes some muscle to really move it, so quick 1 hand steering is much harder.

Diesels also have brakes that work off hydraboost, which draws from the power steering pump that could affect steering ease.

and diesels have stock steering stablizers

Check your tire pressure. Raising the PSI from 35 to 50 in my 285 BFGs made a big difference.