Need help with rattle

[TNMOPARMAN]

OK so a rattle appeared under my car today, cannot pinpoint it but it does seem to be rpm dependent, its there at idle and I can tell a change when shifting from reverse to drive etc...... heres the catch only starts up after driving car for a while?

1971 charger 318

any ideas?

 

[godfatherofchry]

sounds like a mufler coming apart inside????

 

[TNMOPARMAN]

the sound seems like is coming from the front near trans maybe i dunno, could the sound travel back from the muffler? and i did scrape it(muffler(s)) kinda hard today, little to fast over a speed bump that jumped outta nowhere, i mean i didn't get air or anything but none the less could that have knocked something loose?

 

[dbowperson]

Probably bent one of the hangers, or knocked it loose. Is that the first time you heard it was afetr you scraped it?

 

[TNMOPARMAN]

yeah, but like i said it seems rpm dependent and it only starts up after driving like 20 minutes, when i got home after it started i let her sit about 2 hrs went out drove for like 30 minutes and nothing was 200 yards from home and t started, took her out again about an hour ago and nothing but it was only about a 15 minute drive.....

 

[TNMOPARMAN]

OK took a 7 hour trip back home to TN today and nothing! car drove sweet as a nut , and got 20 miles to the gallon (2bbl 318), so i reckon till it comes back not a whole lot i can do