Rattle from under the car durring shifts

At the beginning of second and third gear, there is a rattle from underneath the car. Sounds like it would be a loose heat shield for the exhaust.. but that is not the problem. Is noticeably worse when going up hill. Took apart the shifter linkage.. that's not it. Nothing is lose underneath.. so my guess is it's in the trans? Has anyone had this problem?

Car is a 96 Metro 5spd 1.0L.

Your tranny wouldn't rattle, heh. When your driving, the engine moves around in the engine compartment from torque. When you shift, you release that torque, and the engine relaxes into it's default postition. Sounds like the cat converter's heat shield is rattling against something, but only in the relaxed postition. Try tying a coat hanger wire around the cat heat shield. And check all your exhaust piping for loose areas, since it is a double walled pipe.

Not the trany per say.. but the shifter fork inside. I don't think it's the cat sheild.. but I'll double check. I was under there for a few hours one day trying different things... taking them off, putting them back on.. nothing changed.

Is the rattle like beans in a can? Or more like a muffled clunk? Your muffler pipe could be resting on the rear control arm.

It is a constant resonation for a few seconds. More like a can of beans, not a clunk. Most like the sound of a heat sheild rusting away and the remains ratteling against the body/frame.