Loud rattle/vibration at 3000 rpm

[mike]

So I've noticed that in the past couple days my 95 240sx SE has developed a weird noise at pretty much exactly 3000 rpm. It happens in any gear, and neutral. It sounds like it's coming from the rear when you're in the car, and from the outside it sounds like it's right about where the rear tires are. Anyone ever had a similar problem?

[HaloZ]

u joint maybe? do 240 have a center bearing on the drive shaft?

Are you sure its ur rear wheel?  If its rattling, it might just be your heat shield.

p.s.  i think there like 2 or 3...u can rip them off.

[mike]

It was late and I didn't really get a good chance to check it out.  It's only at 3000 rpm.  Above, it goes away, and it below it's fine.  I'm going to go and check it out more today.  Thanks for the suggestions.

[rabbit23]

mine did exact same at 3000rpm, it was my heat shield and exhaust, i just stuffed an old gasket i had between the two and it quit. it is just a quick fix before i get mine redone next month.  

[opiate411]

I had the same problem on my 92 SE.
I think the same problem exists on the s14 body.
check your first exhaust shield where the headers join to the rest of the exhaust piping.
I got under my car and removed both halves of that part of the shielding, didnt take too long at all (bolts are 10mm i think) not a hard removal, but it may take some wiggling to get the top half off.