I would say finding out what is causing the tranny to go out is the first thing because who is to say that this isn't related to something else that still might ruin the 5-speed when it's put into it. I'm not real good with trannies so I don't know if there is anything else that could go wrong with the drive train that could cause the tranny to go out like that. Your mechanic should be able to check the tranny to see what is failing in it and a possibel cause.