Don't get discouraged if this doesn't work right away.
My steering got so tight it became a 2 hander. I had heard that the power steering fluid could get contaminated. So while having an oil change I had them flush it out and put in a high quality synthetic... Nothing! I then found this forum, went out to the truck and saturated the steering shaft joints with WD while turning the wheel left to right... Nothing! Saturated them again and let it sit overnight... Nothing! I then went to the quarter car wash and power washed the joints, saturated them with PB Blaster to penetrate and finally with WD to lubricate... My steering is now brand new!
This is a great thread as it has saved me a lot of money by not replacing the power steering (as many will diagnose this as), WD -40 did great job initially, a few months ago. Recently it got tight again, so I loosened the top bolt and slid the collar down so I could feel the resistance in the motion of the top u-joint in this steering linkage (the bottom u-joint has a boot and is protected so I didn't bother that one). It showed resistance in one of the two directions of travel. There are 4 tiny rubber sleeves that protect the bearing yolks from the elements, and after pushing a very small screwdriver into the edge of each rubber sleeve and pulling it up, a temporary gap is created that will allow better lubrication. I used WD-40 initially, then dripped oil into the gap (while working the direction back and forth), wiped area off as well as the rusty residue that worked out of the cups, and used a medical needle to inject grease into this area. After a while (about 20 minutes) of working the cups to loosen movement, both direction paths were very loose. I believe I will not have to do this again now that there is grease protecting the u-joint cups.
Thanks to those that correctly diagnosed this issue in this forum!