About a week ago I pulled up to a drive thru and noticed a loud metal sounding rattle coming from under my Expy. (I just came off of about a 20 mile interstate run). It seemed to come and go as the truck was shifted in and out of gear. I had my daughter (with the emergency brake firmly engaged and her foot on the brake) take it in and out of gear while I listened and felt around where I felt the sound was coming from. It was right in the area where the Catalytic converter runs next to the transmission on the passenger side. Not sure which it was coming from. I didn't feel anything by holding my hand on the trans. pan but of course I could not toudh the converter. I didn't notice it for the following week on my short trips back and fourth to work but my next interstate trip and it came back when I stopped at a light. It could be something loose in the converter and rattles as the truck heats up and the idle changes during gear shifting or the transmission. I guess it may be time to invest in the high flow cats and see if it goes away. Any thoughts?

 

I have this same exact problem in my 97 F150. I will be sittin at a light and the rattling will just go in and out. 80% of the people i asked said that is could be one of your heat sheilds and the other ones said it could have something to do with your cat. It seemed to go away for about a week and a half and then it just started rattling again.

 

im not a technician but it happened to my sisters pathfinder and it was the heat shiel so i would just go under there and tighten um up.

 

I will take a closer look when it is cool. Thanks for the tips.

 

Check out this thread, I posted pics were that noise is comming from and there's actually a TSB on it from Fords.

https://www.f150online.com/forums/sh...d.php?t=241520

 

Thanks for the tip. That sounds exactly like what I am experiencing. I think mine is just in the beginning stages and will probably/certainly get worse. I do have the ford extended warrenty for another 15,000 miles. I will get it looked at ASAP.

 

ok check this out. So i was under my truck today trying to figure out why my A/C is still not working and i accidentally hit my wrench on one of the cats and it mad a rattling sound so i hit it again and sure enough the i hear a rattle again. so i hit another cat but this one did not rattle so i looked closer at the one that made a rattle and there is a small flat peice of rusted metal that is just laying there inside that shield thing that surrounds the cat. Now the only thing i have to do is figure out how to remove it.

 

No kiddin!! I'm going to have to check that out ... Once in awhile at a certain RPM I still here something - a different kind of rattle now... Before I clamped mine It was more of an irritating churping sound @ low r's. Thanx 4 the info!!

 

I'll bet it's the heat shield. Mine made this noise and then I found the heat shield was doing it. I used a large screwdriver to bend the piece that was rattling, and then about 2 months later the whole shield fell off. Problem solved since.

 

hey new to this site but we used wire to wrap and tighten cause we couldn't get to ours

 

Welcome to the site. Thread is almost 8 years old though.