had same problem. had a 2 year old battery.. replaced battery...no change... replaced starter clutch ( aka... starter bendix ) with All ***** starter clutch ( thats the brand name) ....it's been bout 2years...no problem...

 

I agree, it's a toss up. Just posting on an opinion. Every weak battery I have replaced starts with a grunt for a while and then starts the banging. In my case, a new battery fixes it for 3-4 years.

The pictures above on the starter gear spur clutch I posted above came from exactly what you are posting.

It was banging and they replaced it. It was taken apart and you cannot tell it from new. So go figure. The only reason I post battery is to start simple. Sure would have liked to see what the problem with your's was. Did you do all the work?