I just recently upgraded my 79 malibu to a 383 that dynoed 562 hp and 500 ftlbs torque. We got everything set in and put the new driveshaft in that I just had cut. We were running around on bald street tires and torqued hard on it a couple times. The next morning I got the car out and notice a small vibration. I checked and under the car the transmission housing has split from one ear to the other. I am not sure what would have caused this. I am just looking for common causes to begin diagnosis and checks. All help appreciated.