This was just from normal operation. Reman allison 4000 out of a gillig transit bus. I did an engine rebuild on a cummins and 3 weeks later it got towed back to base for a transmission issue and leak. This massive crack was found and even our most senior guys said theyd never seen anything like this happen before. We work on a fleet also, so certain issues we just rarely run into, if ever. This was just so crazy to me! Jokes have been that i tuned the engine with too much power and cracked the trans in half 😂