The exhaust fractured properly on my Trabant over the weekend at the point where the middle pipe enters the back box. A support strap had gone and I didn't notice in time to replace it. It must have taken a while for the joint to fracture properly. What I found interesting was the way that as the hole grew it created and amplified all sorts of sounds. Groaning and droning sounds that sounded like crankshaft bearings or gearbox problems. The sound of the engine returning to idle started getting much rougher for some time before the exhaust cracked properly and I wondered if there was something wrong with the pistons or small end bearings. The rattling sound caused by the pipe vibrating against the back box seemed to be coming from the front of the car as if something the dynamo or fan were working loose. I welded up the crack this morning, not my best work, but it seems to have done the trick. Now the odd sounds have diminished or disappeared completely.