Steering hard spots..

You need to replace steering shaft. New shaft has replaceable u joint. When you remove yoke from gear box input shaft you will feel u joint "sticking"

 

Had a recall for that same issue; felt like it sticks or stops for an instant and you can definitely feel it. This was on a Freightliner Century class....cant remember what year the truck was but it was in 1997 or 8 when it happened to us. It was a steering shaft issue like stated above...

 

Yep, I had the same issue and replace the shaft with the new you joints and all is well.

 

I literally just had this happen to me. Start by spraying the joints on the steering shaft with WD40 or something similar and you will probably almost immediately feel an improvement. If it feels better you can probably drive like that for a little longer but it will have to be replaced soon.

 

Had the issue, the wheel well plastic started rubbing on the steering shaft ujoint. Reposition it fixed my.

 

I lowered my pet 579 last year ,,, after that i got hard left turn and steer won’t back to center smoothly,, so i though is gear box i did changed pump and gear box but still have same issues,, would u help me with any idea ?

 

Try adding enough fluid to get to top of filter.. ignore the dipstick.
I've had a clogged filter do the same thing you describe.
I hope you didn't use Lucas or anything like that in the fluid. Synthetic ATF is the best thing you can use...no thick additives.