Solar tracker systems include a torque tube, a column supporting the torque tube, a solar panel connected to the torque tube, and a locking assembly. The locking assembly includes a first end pivotably connected to the torque tube and a second end pivotably connected to the column. A shell defines a fluid chamber and a piston is positioned within the shell. The piston includes a seal and defines compression and extension portions of the fluid chamber. A flow path extends between the compression portion and the extension portions. A first valve assembly controls fluid flow in a first direction through the flow path and a second valve assembly controls fluid flow in a second direction through the flow path. The valve assemblies are each passively moveable from an unlocked state to a locked state in response to movement of the piston.