Brake modulators for parking brake systems of work vehicles are provided. A brake modulator includes a housing defining a fluid chamber, an auxiliary chamber, a fluid inlet channel, and a fluid outlet channel. The brake modulator further includes a piston disposed within the housing between the fluid chamber and the auxiliary chamber. The piston is movable between a first position wherein the fluid chamber has a first volume and a second position wherein the fluid chamber has a second volume greater than the first volume. The brake modulator further includes a biasing element providing a biasing force on the piston towards the first position, a rod extending between a first end disposed within the housing and a second end disposed exterior to the housing, and a handle connected to the second end of the rod. The rod is manually actuatable to move the piston between the first and second positions.