Auxiliary gear box pistons stops

The subject invention relates to a heavy vehicle transmission auxiliary gear box with a power cylinder that uses housing structure other than the piston as a stop. A heavy vehicle transmission auxiliary gear box has a piston housing defining internal fluid chambers. A piston shaft is further included to achieve the gear shifts in the auxiliary gear box. A yoke element is coupled to the shaft for engaging the multi-speed transmission. A piston is disposed on the shaft in the internal fluid chambers to move the shaft and the yoke element between first and second positions. Shoulder elements on the shaft prevent direct contact between the piston and the piston housing when the shaft and the yoke element are actuated between the first and second positions.