Power steering pressure

Your pump could be weak or maybe your fluid and filter need to be changed.. Better grease helps too I find. You may also have a steering shaft that is binding up. Kenworths do tend to take more effort than most trucks I find.

 

Also keeping your fifth wheel well lubed with a moly fortified grease is a must.

 

Usually how tight the steering feels is built into the gear by design. You can make steering easier by having a front axle alignment done and lowering the caster.

 

Or trade it in for a volvo

 

It is not a kidds toy " Sit N Spin" If the tires are rotating slightly the steering wheel effort is reduced greatly. Install a larger diameter steering wheel?
When my shoulder was bothering me I found it helped to keep my hand between 3 and 5 o clock when turning.
I could push a lot but it would take a while to get over a hard pull. It took me a while to figure out what activity reinjured it and what to avoid. I have near complete recovery without surgery but it took a long time.
Be thankful you at least have power steering and use that other hand like you mentioned. Good luck with that.

 

I had a similar problem with mine when they put a new Sheppard steering gear in it, you can buy an oil additive from a steering specialist which seemed to help. Also I've heard you can boost pump pressure by putting a restrictor in the output side, but I'd be talking to a steering specialist about that. Different caster angles could help as well.