Intermittent metallic rattle on acceleration

[TB2k4]

I've started to notice an intermittent metallic rattle on acceleration. I've either correlated it to speed or RPMs. It usually comes in around 25-30mph, 45-50mph, 10-15mph (most-least frequent). Also I've noticed it around 2500-3000 RPMs.

The noise is metallic in nature and increases in frequency with added gas until it just disappears...

Car was just in the shop for a front right bearing, left has been replaced. However, I have noticed that a wheel/brake driving noise has disappeared coincidently. Wondering if someone has had any similar problems and what they found. I've just about had it with this car, the guy I got it from was the farthest thing from honest and something always needs to be replaced.

 

[Mooseman]

Which engine? It's not in your profile.

Mine does the same, 5.3L V8. I just received an oil analysis back, high content of iron and aluminum, no other metals so bearings are good. I think it's in my valvetrain, and the noise seems to come only from the right side. Does it if I rev or when I'm accelerating. At same RPM's while cruising, no noise.

 

[TB2k4]

Straight 6, sorry I've been pretty inactive lately. I put the car in neutral yesterday and revved but didn't hear it. Strangely, I went for a quick errand today and didn't hear it

 

[Tiggerr]

I've heard a similar noise from mine on occasion. Sounds almost like when you are rolling a throw an old TH350 in park. Like that clicking/rachety sound. Right around 2500 RPM. Noticed my shroud is not on quite right, from when I did the water pump in 0 degree weather. Was thinking maybe that was it. Haven't got around to straightening it out yet. Haven't heard noise in awhile either

 

[Real McCoy]

When I read your post, my first thought was a loose baffle in the muffler, resonates at a certain frequency. Mine started to do that at about 75,000. Now has 307,000 miles still makes the rattle on acceleration. On mine, it goes away if I accelerate a little harder.

Doug

 

[TB2k4]

When I read your post, my first thought was a loose baffle in the muffler, resonates at a certain frequency. Mine started to do that at about 75,000. Now has 307,000 miles still makes the rattle on acceleration. On mine, it goes away if I accelerate a little harder.

Doug

Wouldn't it make the noise in neutral then? It only occurs in drive...

 

[TB2k4]

AC doesn't seem to be working... compressor?

 

[Real McCoy]

No it doesn't make the noise in neutral. When you are in gear the engine transfers more vibration at the critical frequency to the chassis and thus the muffler. It only resonates in gear on gentle acceleration. Hard acceleration it doesn't resonate.

 

[JerryIrons]

That was my thought too, the muffler or resonator. (mine has been doing that for years, intermittently) You might be able to go back there with vehicle off and shake it with your hand a little, it will be very obvious if it is.

 

[C-ya]

My initial thought was knocking. Check engine light lit? If not, it will probably be something like mentioned above - muffler, heat shield for cat, or some such.

 

[steveO]

I had the same thing it drove me crazy trying to find it but I finally did...

Check the shield on the transmission the part that curves around the edge of the pan has no bolts in it but It can vibrate against the trans.
I simply bent is away sightly with my hand ...
Noise is gone.

 

[TB2k4]

My case ended up being a loose U joint, glad I caught it before any catastrophe. Just wanted to follow up