Hi, trying to limp my 726 though the rest of the season. The impeller shaft slides in and out of the gear box to the point where the impeller is hitting the housing. There is a cap on the front of the gear box where you can get at the end of the impeller shaft and bushing. Is there something I can easily replace under this cap so the impeller shaft does not slid in and out so far? Maybe throw a washer in there for now? I am planning a rebuild this summer. Thanks in advance.