I have an '03 Cooper. There is an exhaust resonance at 3500 rpm. This car is a 5 speed, so at a decent cruise speed, and 3500 there is a car wide resonation....it's there regardless of gear, and is clearly exhaust. ....any ideas?

 

If it is a stock exhaust, you probably have a leak. If it is not stock, well some aftermarket exhaust do resonate kind of badly. What kind of exhaust is it?

 

Totally stock exhaust...I'll check for a leak.....it's clearly a resonation that gets louder as I rev through from 3000 to 3500, then quiets as I rev up to 4000.

 

I'd also check the driver's side resonator's mounting bracket. Mine is rusted through and causes some pretty loud vibrations... Gotta get another mount.

 

Check out the "Broken exhaust above cat.." topic..possible warranty item?