Abstract: A method of fixing an annular piston onto a piston shaft includes providing an annular piston with a central bore having a diameter slighty less than the shaft diameter, heating the annular piston to expand the bore diameter and then placing the heated piston onto the shaft so that the piston, upon cooling, is permanently shrink-fit onto the shaft. In an end-of-car cushioning unit for a railway car, the prior shaft is cut adjacent the piston and the piston is rebored to a diameter slightly less than the diameter of the end portion of the piston onto which it is to be shrink-fitted.