Truck: 2001 Dakota Quad Cab, 4.7, 5spd, 4wd, 186k miles.

The noise: When free revving the engine, as the revs drop the noice sounds like marbles in a tin can. The noise is the same whether the clutch is in or out. When decelerating in gear, the rattle also appears until about 1200rpm.

This noise does not present when the truck is cold leading me to believe the Cat could be breaking apart. Anyone have a way to check whether it's the Cat or the TO bearing?

This is my DD so please no gutting the Cat suggestions or anything like that.

Thanks,
Danny

 

You singled out the Cat so I presume that's where the sound is coming from...

If so, I'm bettin' on loose heat shield.

Most cats, out of the factory on any vehicle, will have a heat shield around them...
It's very possible one of the bolts, or pieces of the heat shield has rusted out (common).

Check for any loose parts... If that's not it, check around everywhere else for any loose shields, or otherwise.

Short of all that, have you noticed any drop in performance?

 

get a rubber mallet and climb under and hit the cat, if it rattles, it needs to be replaced

 

tap it! don't smash it!

LOL j/k j/k

 

hmm maybe it is the cat i am having a problem like this too and just had my clutch, to, pilot bearing everything replaced and its still doing it so i'll have to tap on mine to and see if that narrows it down any

 

Mufflers can also rust and fall apart on the inside too. Do the same mallet check with the muffler and the pipes going in/out of it.

 

I would guess something is just rattling with the vibrations at the lower rpm's. Like others have said just for anything loose underneath. I'm willing to bet that is the problem.