Can't track down this annoying sound..... :/

2007 TRD DCSB with E-Locker.

Been chasing this really annoying noise for several weeks now, with no luck. Searched, and although I found cases that describe a similar noise, it's not in the same conditions. So hoping someone may have some good suggestions.

The sound:
It's a rattling/baseball card in the spokes type noise. Metallic, almost tinny (if that's a word).

The vicinity of the sound:
Rear. With windows closed, it definitely sounds like it's coming from the rear. Windows open, harder to tell with wind noise - but definitely louder outside the truck.

Conditions:
Very consistent between 55-60 mph only. Under 55, there's no noise. Over 60, it lessens, and is gone over 65ish. It only occurs while cruising, with very light pedal application. Let off the gas, it stops. Give it slightly more gas, it stops. Under any load, or acceleration, no noise. I can make it happen at will.

What I've checked:
At first, inside the cab, I thought it was simply something behind my rear seats vibrating around. Nope. Cleared everything out, and that wasn't it. Went into the bed and tightened and removed anything that could possibly vibrate on something. Wasn't it. Checked the exhaust, since it definitely could sound like an exhaust leak or rattle, which would explain the light throttle conditions. Tightened it all up, and made sure it wasn't near anything that could rattle. Not it either.

I've also swapped to my backup driveshaft, thinking maybe the CV joint or carrier bearing was going - no difference.

I'm really hoping it isn't diff/axle related. I've got 4.56 Nitro gears. The noise became much more pronounced after an off roading event a couple weeks ago.

Any help/suggestions would be great!

 

Did you check your cat shield? Maybe something got between? Maybe lost a bolt.

 

I only have the upper cats, which I don't think have shields. But i also don't think I checked that far up the exhaust, so I'll get up and take a look in that area when it cools off a bit. Thanks for the suggestion.

I'm also wondering if perhaps the rear brake shoes are falling apart, and rattling around at certain loads - but can't see why load would make a difference there. I'm sure baffled.

 

My spare stock tire used to rattle, cleaned the mud off of it and flipped it over so that the wheel face was down towards the ground....and the rattle went away. My leaf packs also squeak, my gas tank heat shield rattles some times, the heat shield on my rear cat on the driver's side rattles.

Pulling the drums may not be a bad idea, when i pulled mine....the spring kit on the driver's side flew apart and almost it me in the face (that was not long after getting the truck) fortunately there was no uneven shoe wear and all i had to do was put the springs and clips back on and readjust.

There are plenty of things it could be

Best of luck

 

X2. I'm guessing it's a heat shield somewhere. Not necessarily on the cat; there's a couple of them located along the body as you follow the exhaust back. May not even be the heat shields themselves; maybe there's a rock or something stuck in one of them.

 

I did check all the shields to make sure they weren't contacting anything along the way, but I didn't check behind them to see if something is wedged up there. I'll check that too.

 

Lets hope it just some gravel in between.

 

Maybe the exhaust "hanger" bolts and washers? Mine were loose at one point and the washer would rattle around and make the metal "zzzzzzz" sound.

 

It just occurred to me that a 2007 has been in service for 7-8 years...
Climb underneath and bash the Cat with the meaty part of your fist, like you're pounding on a table. See if it rattles. Hopefully it doesn't.

 

They're welded on with the 2nd gen.

I checked for rocks and heat shields. All look fine. Suspecting that it may be coming from the diff . Just can't find anything else it could be. Project for this weekend I guess.

 

Welp - pulled the 3rd member out this weekend to fix a small leak that I've had for a while. While I was at it, pulled the brake drums off and cleaned everything out and adjusted the E-brake. The noise is gone now - although I'm tempering my excitement till I can be sure it doesn't come back in a few days.