Steering will not turn to the left??

[1999chevy2500]

Hello all, I have a 1999 silverado 2500 4x4 which is the transition year newer (2000) body style.  Truck is lifted 8 inches, everything steering wise is new.    the steering gear box was replaced once with a cheap style box from discount auto seemed to drive okay for a bit then the steering locked up, it will not turn to the left.  The steering gear box was replaced a second time lasted about 3 weeks and did the same thing??      turns to the right will not turn to the left.

 

This time I checked the fluid in the power steering was a bit low , not sure if it is burnt out or not that would cause the problem?     Should I replace the gear box with a Red Head Steering gear box??   Should I replace the power steering pump also?

 

Has anyone delt with this?