I've seen a few threads about stiff steering, but no solid solutions as to fixing it.
The symptoms are when you turn the wheel, and the steering goes from stiff to normal to stiff throughout the steering wheel rotation. As if there are stiff spots as you turn the wheel. A constant stiff steering is another issue.
Spray the snot out of your steering U-joint just above the steering rack with a penetrating oil. Keep turning the wheel 1/4 turn to expose the different sides of the joint. You can easily access it from underneath the truck. I used SeaFoam as it penetrates decently and also lubricates, unlike WD-40 witch penetrates well but doesn't lubricate as well.
No more stiff spots in the steering. This should get you by for a while until you need to replace the u-joint.