If you don't replace it now you will be replacing it within the next year or two anyway. Everyone has different opinions on this but I feel anything over 3 years is gratis. If it's a 24 volt system for the TM you will need to replace both. The weaker one will shorten the life of the newer one, or so I was told by several folks when I did mine. Also, one more thing off your mind that will let you focus on the fish, I hear Canada has a few.