On my 20001 chevy silverado 1500 Z71 engauged 4x4 and then steering wheel got hard so hard to steer desangauged still the problem persist

There may be an issue with a pressure control valve.

I cant picture your setup from memory. Does your truck have a horizontal shock potentially infront of the front axle? It would be there to give you that "road feel/resistance" and if worn out wont do anything.

2004 chevy tahoe 4x4 had the same problem wont turn right at idle - like no power steering , has hydoboost brake steering system , did test and found steering box bad , removed box and remove the top cover on box 4 bolts at hydralic cover and removed and found spool valve has 4 seals 1 outer was blown i replaced box with reman from advance auto about $200.00 and flushed system , drove great problem solved .

Yes it is

The trucks like yours have a rack and pinion steering, and when rack and pinion steering need replacing they get hard to turn in one direction just as you have described.

Chevy is having problems with the steering columns on these models. Feels like a jiggle in the steering wheel when you hit a bump of any kind. Cost about $75 at the dealer for a new part.

Have the drive shaft checked out. You may have a bad hub bearing or bad CV joint. Look for cracks in the boot, and grease that has been flung inside wheel well

try selecting from nutreul or less then 3km

this should help let me know

Maybe got an air lock/bubble