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Ask Jerry Your Own Question
Jerry
Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1740
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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At 1900 rpm, rhythmic harmonic sound. No vibration, 96, just

Customer Question

at 1900 rpm, rhythmic harmonic sound. No vibration
JA: What is the model/year of your Dodge?
Customer: 96
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: just driving it
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 1 month ago.
Category: Dodge
Expert:  Mike S. replied 1 month ago.

Hi, I am Mike, welcome. I'm reviewing your question.

Expert:  Mike S. replied 1 month ago.

Does the sound happen in park or neutral, just reving the engine up to 1900 rpm?

Customer: replied 1 month ago.
Truck has 500k on it. When driving in any gear when approaching 2k rpm. Engine has never been touched, still runs great , minimal oil usage. Could it be piston slap?
Expert:  Mike S. replied 1 month ago.

I don't know yet. If yo are not going to answer my questions, this is going to go nowhere cause I have more to ask, second is, is the noise coming from the engine?

Customer: replied 1 month ago.
Have not tried it in neutral
Expert:  Mike S. replied 1 month ago.

Are you near the vehicle right now?

Customer: replied 1 month ago.
no
Expert:  Mike S. replied 1 month ago.

Ok, let's go by memory just for now.

Does it sound as though it's coming from the engine?

have you ever reved it up higher than 2000 rpm and if so is the noise still there and if so is it louder?

Customer: replied 1 month ago.
Only noticed noise this weekend. Have not tried reving it yet. When going down hill and it kicks into a coast state noise goes away. Pretty sure its the motor. Trans has temp guage and not overheating. Just a very rhythmic humming sound
Expert:  Mike S. replied 1 month ago.

I am waiting for an answer?

By the way, it is my opinion that position slap would make a noise standing there under the hood reving the engine up by hand in park/neutral.

Customer: replied 1 month ago.
I can change noise dynamic by accelerating or decelerating.
Expert:  Mike S. replied 1 month ago.

Humming? Does the fuel pump ever make that humming noise when you first turn the key to run before you turn the key to start?

Expert:  Mike S. replied 1 month ago.

Ok, never mind, it's not the fuel pump.

Expert:  Mike S. replied 1 month ago.

Do you have an auto or manual transmission?

Customer: replied 1 month ago.
old school '96..No electronic crap
Expert:  Mike S. replied 1 month ago.

And what model is this, what engine and is it 4wd or rwd?

Expert:  Mike S. replied 1 month ago.

My 1985 has an electric fuel pump.

Customer: replied 1 month ago.
5.9 L 4x cummins
Customer: replied 1 month ago.
Maybe harmonic balancer? But no vibration just the rhythmic sound
Expert:  Mike S. replied 1 month ago.

Ok neither of those is the model, and I suppose the 4x means 4wd, what about the transmission?

Customer: replied 1 month ago.
Automatic. Dodge Ram 2500
Expert:  Mike S. replied 1 month ago.

I don't know if it's even possible to hear a piston slap on a diesel. I am not a diesel mechanic either.

Customer: replied 1 month ago.
I read piston slap will give a hollow sound, which it does but that very distinct cyclical hum is troubling. It's not real loud but I hear it. Maybe just a well worn engine sound.?
Expert:  Mike S. replied 1 month ago.

One last question then I will opt out in case you want to talk with a diesel expert. If you feel safe doing so, please practice a few times but on a long stretch of open highway with no one else around, get it up to speed to when the noise occurs, then shift into neutral and listen if the noise is still there or not, if it is, shut the engine off just briefly, then start it back up and listen if the noise went away that little time the engine was shut off.

Customer: replied 1 month ago.
hold rpm's steady?
Expert:  Mike S. replied 1 month ago.

No, get it up to speed to where it makes the noise, then let up on the accelerator, then shift into neutral, then shut the engine off, just for a few seconds.

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