Steering stiff

Replaced the steering gearbox. Refilled power steering reservoir and "burped" it. Steering was very stiff for first few minutes of test drive but loosened up and was fine for rest of 10hr night. Truck is a street sweeper. Next day, could not hardly turn steering wheel and only slightly better after a few minutes of driving. Replaced PS pump about 4 months ago. Have heard there is an adjustment on PS gearbox. What is it and how? Yes it was p/s fluid. I don't see anything on the gearbox that looks like it could be used to make adjustments. I guess biggest question is why it was fine for a 10 hr work night sweeping parking lots, with all the sharp turns and such and then next day you can't turn the wheel while sitting still and takes both hands (Armstrong steering) while moving.

It's possible but can't see the pump failing in such a short time.
Thanks for your time. Thanks!