Erho78

So i had my transmission worked on a couple weeks ago, and I was going to take it back in for a follow up. Before I could, it started making this loud, obnoxious metallic noise (kind of like putting ball bearings in a metal tumbler), coming from the underside, not the engine compartment. The truck ran fine, shifted fine, just annoyingly loud.

The noise persisted, whether the truck was PARK, DRIVE, REVERSE, whatever. About 2 blocks from the transmission shop, the noise ceased! lol figures! And they could not recreate the sound again, after several test drives.

The noise began when I went to pass someone, and the truck downshifted...made a loud squeal, then the fast rattling began.
ANY IDEAS ON WHAT IT COULD BE??? Any help is very much appreciated!!

Truck: 2007 F150 4door w/ 4.6L
Trans: 4R70W

Eric ~ "Erho78"

izzysplace

Catalytic converter blew would be my guess. Not sure if your truck runs a single cat per side or double cats per side, but if the element had clogged or over heated and fused it could or possibly did shatter. The noise you may have heard were all of the fragments of the catalyst rattling around, eventually they break up into smaller bits and pass out of the exhaust pipe.


Depending on how bad the failure was you may soon have a check engine light come on.

Erho78

I didn't even consider that! I just kept thinking mechanical..but I knew if there was something rattling around the trans or engine, it surely wouldn't be running as well as it is. Thanks for your feedback Izzy!

bourgeois1269

Heat shield is a possibility also. It took me 6 months to find this annoying rattling caused be the drivers side heat shield so I used 2 of those metal clamps that tighten down screwing the hex head nut and no more rattling after that.

JLBlazin00

Sounds like a cat my truck rattles at a low idle from the drivers side rear cat once the truck gets nice and warm it tends to go away