Everytime I start my 1998 Ram1500 and shift into drive or reverse it make a loud "rattling" noise under the truck. I check the muffler, converter but everything looks normal, not loose. Any idea of what's going on? Thanks!

 

Try hitting the cat with a rubber mallet. Loose internals is a common issue on Chrysler/Jeep cats.

 

You also might look for a loose heat shield. I know Ive got one bugging me right now but I havent had the time to throw it up on the lift to see.

 

^there is a heat shield over the cat, on the side of the gas tank and above the motor mounts. on of the motor mount heat shields on my sisters truck was bent a little and used to rattle.

 

I think I have the same problem as you. At idle there is lots of rattling and drone noise caused from the muffler (I have it dumped right by where the bed and cab meet). I think it is just because of the muffler placement and it is causing everything rearward of the muffler to rattle like hell. I need to get a different muffler (Flowmaster Super 44) and have an exhaust shop build me an exhaust and tailpipe that will exit like the stock system.

 

Thanks guys for your responses!!! Yeap!.....the cat is the problem. Now I need to find out how much to replace it.

 

210$ since you live in CA.

it would be 70$ if you could get a universal cat.

 

Total with parts and labor to replace it $1,300

 

That was the first thing I had to replace on my ram.. costed me $713.36... I was at college at the time and didn't have my tools or shop to do it myself

 

You really might want to consider getting a 50 series.. I have mine dumped right between the cab/bed and my 40 series was loud as hell... 44 would be just was loud... lots of drone on the highway too with the 50 series you still have that aggressive exteriour sound, but the cab noise (drone) is pretty much cut in half! and can actually carry on a normal quiet conversation inside.. while outside you loud *** muffler sets off car alarms as you drive by! It's the best of both worlds!.. IMO