I don't have a manual for the 550 yet. I have several for the 1800 (I&amp;T's and a factory shop and parts manual) and the 1650 (Couple of different compilations of I&amp;T's.) I didn't know if there would be enough similiarity in them for guidance.

Kind of looks like,  maybe second gear got the grinding stone...

The shafts that go into the 608 from the rear are where the welds are. I'm going to guess the problem is in the low range. 

Thanks for the pictures Chris. I'm off to the shop to perform surgery and see if I can save this... This is why we don't allow cavemen to work on things with fire and rocks.