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I have a 2011 Ram 1500. For about a month I thought I was hearing a clunk between 2nd and 3rd gear. I finally decided to listen carefully by turning my radio off. I now certainly notice it, but it is very specific. It is more of a grind than a clunk when I listen closely and comes from the front of the truck. It is not between 2nd and 3rd gear, it was just a coincidence (I think). It happens before shifting as well.

That is when I noticed it only happens when I am accelerating very slowly and maintaining a low RPM. (I would guess around 1500 RPM). The constant seems to be the speed. It seems to happen between 24-26 MPH, which just happens to be when it shifts sometimes. If I accelerate too hard I never hear it. If I don’t accelerate at a constant speed, then I do not hear it. So at a constant RPM, right around 25 MPH, I hear the grinding sound. It only lasts for a split second. I can almost always repeat the sound if I accelerate correctly.

The only thing is, today, I heard the same noise at about 17 MPH while accelerating after a turn. I also thought (not 100% sure) I have heard it at faster speeds a couple times (40+ MPH), but the traffic/wind is too loud to know for sure.

Does anyone know what this sound could be? This is my first question, so let me know of any edits or information you guys need. I am just guessing the motor or transmission. All I know is it is coming from the front of the truck.

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Did you ever find out what the problem was with this? –  user4100 Dec 5 '13 at 18:05
    
The guys at my local Dodge dealership cannot find the problem, but acknowledge the sound is there. I think I found the problem, but they won't agree with me. I have a cold air intake. The sound is made shortly after I go into "eco" mode. I think it is the sound of 4 cylinders shutting down from 8. When I accelerate after hearing the sound, my truck lags for a second until all 8 cylinders kick back in. Also, when I turn off eco mode (by manually shifting into 5th gear) I cannot reproduce the sound. So these two things make me pretty sure that this is the issue. –  l3v Dec 5 '13 at 21:20
    
I think the cold air intake makes the cylinder shutdown noticable, which is why most normal trucks don't have the sound. Just my guess, though, I am not a mechanic. So I don't think it is a problem other than the sound. Awhile back I read a forum where somewhere referred to this sound as the "MDS fart". –  l3v Dec 5 '13 at 21:21
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1 Answer 1

Your best bet would be to have someone in the truck (in park, with e-brake on) to hit the gas while you are under the truck. Make sure they know what sound to look for first, and when the sound happens, have them try to keep it going so you can determine where it is coming from. Since it seems to happen at a specific RPM range, you should be able to replicate it while it's in park.

Also, if it happens while it's in park, you can pretty much discard the transmission as the source. It could quite possibly just be something loose under there that only rattles when a certain pitch resonates (this happens with heat shields a lot), but again, it's impossible to tell until you get under there to determine the origin of the noise.

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Thanks for the advice, I will let you know how it goes. –  l3v Jul 26 '13 at 13:47
    
No problem, good luck. –  Tip_Top Jul 26 '13 at 13:53
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