Rattle after accelerating...

[Stoked]

Not that concerened, but feel it may cause me problems in the future. After strong accelerations and letting off the gas completely, I hear a weird rattle while the engine is revving down (1-2 seconds). Im thinking camshaft/valves?

[Trail X]

You sure you're not hearing excess gas burning off in the exhaust? It kinda creates an extra pop or crackle. Do you have your resonator deleted?

You're really going to need to supply more information of where the sound is coming from and what it sounds like.

[Stoked]

Definitely not backfiring. Sounds mechanical and from the engine. I know my fan clutch is done, havent found the need to replace it. Maybe it can be the fanclutch changing speeds faster/slower than the crankshaft

[dvanbramer88]

Definitely not backfiring. Sounds mechanical and from the engine. I know my fan clutch is done, havent found the need to replace it. Maybe it can be the fanclutch changing speeds faster/slower than the crankshaft

if it sounds like a "chop" like the sound that earned helicopter's their nickname "choppers" than possibly the fan.

[MrSmithsTB]

I have recently noticed something similar. Never under load, but when coasting or slowing I hear a faint rattle between 1100-1500 rpm. Almost like if bb's were tumbling in a jar or something. I haven't been able to pinpoint it and nothing is obstructing anything. My fan clutch and water pump are only 6 months old.

[Stoked]

Another interesting note, the frequency of the rattle slows with the engine revving down which is why I continue to believe that its engine related, not something thats loose and rattling.

[dvanbramer88]

Josh has the performance high flow muffler and if he rev's it up as it drops through that range in rpm's the muffler pops a little bit, but is a distinct exhaust sound, not the motor. I'm trying to help but idk what to tell you, a traditional "tap" is usually under load and/or when it is cold out. Is it "pinging"? try a higher octane fuel on your next tank to see if it goes away.

[bgwolfpack]

Have you checked the motor mounts? They've been pointed out before as "funny noise makers".

[Stoked]

Yeah my motor mounts are gone, but it gives a nice plesurable vibration, kinda in the same way a washing machine would

Dont think that would be it though. The rattling frequency matches with the RPMS, so it has to be something that turns in the the engine (fan clutch, crank shaft, rockers). Im giving up on this.

[TransAm-98]

Maybe a broken catalytic converter. I've had a couple cars where the welds broke inside the cat, allowing the core to rattle around in the housing. It sounds a lot like what you're describing. Should be easy to tell once you get under the car.

[Stoked]

Nope, definitely not. I know what you're talking about, my 5.0 had a broken fuel regulator and ran super rich. Went though a few cats.

Again, engine related, goes up and down with RPMs.

[MrSmithsTB]

Have someone else start the truck while you listen with the hood open. It may help you to pinpoint it. Pretty sure I have determined mine to be a loose heat shield. Just have to find it and rip it out.

[Stoked]

Have someone else start the truck while you listen with the hood open. It may help you to pinpoint it. Pretty sure I have determined mine to be a loose heat shield. Just have to find it and rip it out.

Tried this, can only duplicate when moving, so then there goes my hypothesis of it being an engine component . Thanks everyone for trying to help out so far.

[damien]

I have also developed an odd "rattle" while on my last road trip which i took to be a loose heat shield or possibly a dust cover on a rear brake (changes from a rattle to a high pitch whine almost whit higher rev's )
Once i had it up on the hoist at work a found that by pushing on the tailpipe in a front to rear motion recreates the same sound with only my ears in a working shop i was only able to narrow it down to being between the front of the flex pipe and the front six inches of the muffler , therefor i am thinking either a cracked flex pipe or loose baffle.
Not sure if it will help you any but just give try nudging your tailpipe with your foot next time you get in your rig .

[bilit66]

Has anyone figured this noise out yet. I have the same noise. Coasting down to about mph. If I put it in rd gear the noise stops. If I tap the gas at all the noise stops. It sounds like a ball on a roulette wheel. I took it to the dealer and they said it was the sprague gear in the transmission. They replaced it and that is not the problem.It is driving me nuts. I don't want it to turn into an actual problem.

[dvanbramer88]

The rattle sound a can of BB's makes, my mom's jeep made that noise for a while. One of the clamps on the exhaust pipe rusted away and it was one of the joints in the tubing making that sound. Also, Cat heat shields are known to rattle on early 2000 Gm's. My uncle's truck does it. Can't stop it, he dented, bent, creased the heat shield numerous times trying to make it more rigid, hasn't helped. Also, it could be related to the extra vibration of bad motor mounts. My dad's pickup had a bad front U joint that added a ton of vibration. Since he fixed it, alot of interior rattles and squeaks have stopped. Look into that first, it might make other noises go away.