A modular linear transducer assembly is mounted between relatively displaceable piston and cylinder members of a hydraulic roll gap control arrangement in a four-high rolling mill stand. The piston and cylinder members have coaxial openings centrally therethrough which receive the modular transducer assembly. The transducer assembly includes axially displaceable sleeve and plunger members, one of which is attached to the piston member and the other to the cylinder member for displacement therewith. The plunger supports a low voltage differential transformer coil having an axial passageway therethrough, and the sleeve member supports a core rod which extends into the coil passageway. Relative displacement between the piston and cylinder members imparts corresponding relative displacement between the coil and core rod to produce a signal indicative of roll gap change. The positions of the coil and core rod relative to one another are adapted to be adjusted at opposite ends of the modular transducer assembly without removing the assembly from the piston and cylinder members, and the transducer assembly is adapted to be installed and removed as a unit with respect to the piston and cylinder members.