Diesel Bombers - g56 cracked by starter

Ok guys I have cracked another g56 in the passed but the cause was a south bend clutch that became out of balance and caused the bell housing to crack. Anyways I put the new tranny in right about a yr ago with a new clutch assembly. No issues everything was great. Until today drove it allday got in it hit the key it made a weird noise. I thought I let up on the clutch a bit and the starter just hit and stopped. Well that wasn't the case. It broke the adapter plate and the bell housing where the starter mounts. First thing I thought when I seen the crack was maybe hydro lock for what ever reason. I wasnt very happy so I just pulled started it. Stupid? Maybe I didn't really care it was already broke. Well it fired up ran just fine. So pretty much any ideas for what could cause this. ( my truck is not raced or sled pulled with strictly a daily driver). Thanks for the suggestions. Also a g56 or south bend clutch will not go back in this truck.