Apparatus for mounting an air brake cylinder to a bolster casting of a railroad car includes an adaptor mounting plate disposed contiguous to the surface of the bolster casting. The plate has a plurality of holes formed therein. The bolts are inserted through holes in the bolster casting and through the corresponding holes in the plate. Nuts are torqued onto the bolt shaft to secure the plate to the casting. The adaptor mounting plate also includes a plurality of threaded studs welded thereto. A flange is welded to the cylinder housing at the rod end of the cylinder. The flange has holes formed at its four corners. The flange and cylinder mate with the adaptor mounting plate such that the threaded studs on the plate are inserted through the corresponding holes in the flange. Nuts secure the flange to the plate. Holes are formed in the interior of the cylinder to accommodate the bolts and associated nuts securing the bolster casting to the plate. The apparatus of the present invention allows a single person to complete the entire assembly of the cylinder to the casting.