When we were kids we had a fifty four 3/4 ton chev. pick-up with the big six cylinder. Running back and fourth around the farm we used to key the ing. ( turn the motor off & on ) while running down the road. It was better than any M-80 fire cracker and enought to blow the muffler to pieces more than once. Being on the farm us kids always found another used muffler to replace before dad found out about it. We even buried a blowen out muffler one time to hide the evidence.
It's possible you may have a loose connection in the ing. wiring which caused the loud suprise when you hit a piece of rough road ??
