Quite possibly the 4013HXT has a peerless Hydrostatic Transmission. Check for a model number on the case of the hydro. If it does there is some good help on working on it but many mower shops only want to sell you a new one since working on it can take quite a bit of time. My Victa is a 4616HXT aand while it is a murray clone it was made in the NOMA factory instead of the murray.