Bad gearbox?
 

I’m been having some issues with my steering lately. When stopped in a parking lot I can not turn the steering wheel either direction till I start moving. If I put it into drive with my foot on the brake it still won’t turn unless I start moving and it can be just a tiny bit of movement then it will turn. I just replaced every steering component except the pitman arm but I’m starting to think I need a whole new gear box. I did adjust it about a year ago to remove some play. Any suggestions to check before replacing?
its a 2000 blazer 4wd with both rc2.5” lift and pa 2” lift and sitting on 31” tires

It almost sounds like the power steering parts of it are not working; pump, plugged hose. I would think you would have heard the pump if there was low fluid.

I’ve checked it multiple times thinking it’s low. It’s like as soon as it starts to turn it hits full lock without turning

Look for a wheel bearing or brake caliper seizing up. The wheel and tire cant respond to force (can't move sideways) from the pump if the wheel is locked. Or lift the front wheels and see if it steers.
Remove the front wheels and turn the hubs by hand and feel for rough rotation of the wheel bearings.

Drive from the transmission makes the wheel rotate on the axle, the steering makes the wheel rotate in a line vertically thru the wheel- up thru the suspension. If the wheel locks, the tread will glue the tire to the pavement and resist the steering force.

Also the PS pump could be bypassing - there's a pressure relief valve somewhere and the pressure will be high at that instant.

My pump does whine abit but the fluid is full and my only issue is when I’m stopped or leaving from park and trying to turn right away