Rounder L1000 skidsteer

Good day guys I'm rebuilding a L1000 from top to bottom. I have the Wisconsin VH4D all rebuilt ready to rock. Before I did the tear down I noticed that the one side of my steering was not as responsive as the other. When I push the lever all the way forward it barely wants to move while the other side has great range. Could this be a drive motor problem. All the linkages are in great shape. And all other hydraulic fuctions work properly. Or is there a check valve somewhere that might be stuck.also I'm looking for the service Manual for this model. I have the parts manual but the service manual would give me all the recommended settings and setup procedures. Any help would be greatly appreseated. Thks.

If it's hydrostatic drive, it could be the motor or pump. The best way to know is swap motors from side to side, see if the problem moves.
Orings do harden up and fall apart in drive motors reducing power.