you'll want to check all your pressures first
Hydraulic Pump
Type Gear
Priority Flow 10 liter/min (2.64 gal/min)

Relief Pressures
Steering (at Pump) 10.6 to 11.7 MPa (1540 to 1700 psi)
Primary (at Control Valve) 21.37 plus or minus 0.5 MPa (3100 plus or minus 75 psi)
Secondary (at Control Valve) 15.5 plus or minus 0.5 MPa (2250 plus or minus 75 psi)

if all those are at correct settings then you might need to check for something binding at the wheels or just by some slight chance you have a flaky priority valve or relief valve or even possibly a flaky orbitrol valve.