Exhaust Leak?

I recently had my transmission repaired at the dealer. It was taken out and put back in. I now have what sounds like an exhaust leak when it is first started.Then it goes away. After it sits awhile it comes back when started. Before the transmission repair I did not have this problem. Does the exhaust come off when the tranny is removed? When you hear the noise with the hood up you can smell exhaust and feel the air with engine rev.

When I took my tranny out I had to take out the exhaust. I would bring it back to the dealer and tell them they didn't put it back together right.

Took it back to the dealer and it was a couple of loose bolts to the exhaust. Thanks for the help!!