Apexi N1 Catback stopped making deep rumble sounds?

[L1lLPANDA]

2 days ago my transmission(auto) ****ed up on me and i didnt know what was wrong with it before, so i drove it to my girlfriends house(at around 4-5 rpm the whole way there due to my transmission) so her stepdad could look at it and on my way over there my exhaust stopped making sounds right when i got off the 605 South Street exit.... :[im getting a new used transmission so thats taken care of but does anyone know what happened to my exhaust?its an apexi n1 catback