I have a 1999 Ram Quad-Cab and have a rattle (or rather more of a knocking) under the front passenger floor. What do I need to be looking for? It is driving me insane!

 

Dont know exactly but im thinking its the cat, mine is doing the same thing.

 

Sounds like your cat is using the last of it's 9 lives.

These Dodge's develop the "cat rattle" when the catalytic converter deteriorates on the inside. Since you're going to have to replace it you might consider a high flow cat to provide increased power. Several other members of the forum have them so ask for their input on which brand is best.

 

yea I had the cat rattle as well, that all went away when I cut it off, but got replaced with noise rattle. the cat chunked and parts of it fell out when i shook it.