2013 chevy 1 ton dually

machunt wrote:
I had new tires installed onmy dually, and they insisted on only putting 60lbs in the rear 4 tires and 78 in the front. i see on the placard it calls for 60 in the rear, they are 80psi tires. i always ran at 80 psi when towing. why 60psi

Do the math. To “need” the full 80psi in rear duals, you’d need to have about 10klbs on the rear axle.
Otherwise, run whatever pressure you need for the weight.
You can run too high of pressure if you want. It will only result in a rougher ride, less traction and potentially premature tire wear (but not prevalent on skinny Dually tires)
When I used to plow snow with a dually, with only a 1000-2000lbs in the bed for traction, I’d run the rear tires at 25-30psi, similar to when driving with no weight in back.