Rattle on decelration....what is it?

[Nismofreek823]

My friend has a 96' 240sx SE with 173,000 and an automatic trans. Whenever we're driving it or just reving it in the driveway it rattles at just above 3,000 rpm. It doesnt sound like a timing chain issue because I have a 92 240 and his timing chain sounds just like mine. i cant think what it could be though. any help would be appreciated?

[silkk]

Maybe the motor mounts are shot? :|

[Nismofreek823]

if that were the case wouldnt it be at all rpm ranges and not just 3000. we just played with it some more and if we hold it at 3000 it continuously does it. I checked the heatshields, the lower one was loose so i held it but the rattle didnt seem to change.

[s13sr20chris]

good chance of some exhaust heat shield rattle. could also be cat converter coming apart or some odd loose item. prob exhaust.

[skydragoness]

You'd be surprised what can manifest itself at 3krpm.

I have a new catco, but last month i had a terrible sounding rattle at exactly 3krpm. Turned out to be my exhaust manifold's heatshield was being held together by one rusted bolt. Upon taking it off, my exhaust is much quieter now.

[Nismofreek823]

well we were able to fix it. once we got it up in the air you could see the lower heatshield was rusted through along the joint to the other half. had to rip it out. thanks for the help guys, i didnt think it was a heat shield until then cause i figured it would do it at all rpm ranges. thanks again.