I have had my 95 Z about 7 months now and the problem is getting worse. It sounds like a metallic rattle right under the center console. I have been under the car about 5 or 6 times and have yanked and banged and cannot duplicate the sound. Nothing moves down there and I am a strong guy. It happens at speeds over 60 and or if I hit a bad bump going slow. It will rattle even on smooth roads when I am cruising at at 60 or over. It is really loud and sounds like something is broken and swigning up and hitting the floor pan really really fast. Like a really fast tapping that goes on forever. The only thing that I can think of is that there is about 1/8" gap between the exahust I-pipe and that tunnel brace that goes over the drive shaft. I am thinking that maybe the pipe is hitting that. However, when I yank on it I cannot get the two to touch. Does anyone else have this problem? What could make such a loud noise when nothing moves?

 

I could be wrong....but this definately sounds like an opti-spark problem.

 

How so? The noise is comming from the middle to rear of the car. I have no audible knock or hesitation and no loss of power and a clean pull all the way to redline. The car runs awesome and still gets 29mpg. I have 44K on the clock now. I am not ruling out anything but I think maybe my exhaust is oscilating at speeds against the floor pan some how and I am not strong enough laying down to get the exhaust to repeat the noise.

 

The fact that you are asking how kind of scares me. Of course its not the opti. But everyone seems to say the opti is the problem to like everything. Its most likely the heat shield that is above the passenger side cat(whick it right next to the tunnel[center console] there. I have the same thing. Though mine has been removed and put back on. I have torn down the whole underside of the car. There is also another heat shield that sits on the passenger side(and drivers) that is above the bell housing but that one is mounted well so I dont think that one would be rattling.

 

I will check that heat shield above the cat. I have not looked there yet but that could be the culprit. No joke about the opti. it seems that everything is to be blamed on that and I dread the day mine goes out. Anyways, I will be back under the car yet again to see what I can find. This time I will look in the tighest of areas. I can see around the y-pipe with ease sine I only have the single cat but I am not sure I yanked on all the heat shields. When you took yours out did the rattle go away? I would think something is completely coming loose because of its degrading nature and sound.

 

I got catbacks and mine (catbacks) hits the floorpan once in awhile and rattles. Tried everything and cant get it to stop.

 

I know these cars rattle since I own two of them but this is not your normal f-body rattle. If I yank in the tail pipes I can get a similar rattle. I just don't know what is causing it to rattle for minutes on end at such a fast pace. I am planning on really getting under there today or tommorow. I will let you guys know. Thanks for the replys.