Rattle Echoing from Center Divide???

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Driving along the highway and with very little vibration or bump in the road, there is a metallic rattling noise that echoes off the center divide and I can hear it as I'm driving. The sound is very similar to a loose muffler/exhaust system that is rattling around but its not because I know its all secure. Everything under the truck is fine as far as I've checked... no idea where else to look into.
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Ok now I'm hearing it periodically when I'm driving, and doesn't even need to be hitting any bumps or anything. It will rattle like something is grinding or caught in the wheel and then go away. Its a metallic sound, so its something lightly rattling up against each other.
 

woody79

Member
Dec 3, 2011
351
Not much help I know sorry, but I have been having this issue for about 2 months. I have looked over all steering and suspension parts and everything seems nice and tight/secure. I even looked under the truck.

At first I thought it might be something in the door frame, but could not find anything there either.

It has me puzzled :confused:
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Like I said it almost sounds like its the exhaust manifold heat shield or something thin and metallic. But it comes and goes, its not just constantly doing it. It does it when I'm coasting on smooth roads, so its not like it triggers only with bumps.
 

04tbottawa

Member
Dec 7, 2011
10
DenaliHD66 said:
Like I said it almost sounds like its the exhaust manifold heat shield or something thin and metallic. But it comes and goes, its not just constantly doing it. It does it when I'm coasting on smooth roads, so its not like it triggers only with bumps.

The noise is coming from the internals of your muffler. Take a rubber mallet and hit the muffler, you wont need to hit it hard to hear it. Mine does the same thing the only way I found out what it was after checking everything else, was when I was on my back under the tb looking around and my son sprayed me with the garden hose. It scared the crap out of me and I tried to sit up for some stupid reason and hit my head on the muffler and instantly heard the noise. I can get a direct fit walker quietflow ss direct fit muffler locally for 120 bones. So that looks like my next project.
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Ah man see I was right in that the sound was definitely an exhaust one. I mean I thought I tinkered with hitting multiple areas of the exhaust last time I was under the truck, but maybe like you said it only takes a little tap. Mine is an aftermarket Flosound muffler though, not sure if you were indicating yours was stock or what. I'd like to get a high flow cat and replace it with a better muffler when it comes time.
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
I noticed the rear brake shields are so corroded and falling apart, so maybe they are rubbing against something. I'll just have them removed.
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Ever since getting the brake shields trimmed the noise has gotten slightly less apparent, but still noticeable. I was thinking about just replacing them since you can't get rid of them anyways. I was looking at Rock Auto for them and they might have metal ones, which would be nice since they wouldn't corrode and break apart like the OEM plastic ones. Anyone else replace theirs and where you found yours?
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
[SOLVED]

Had front wheel bearings and CV Half shafts replaced. Assuming it was the bearing because this noise started first, then the roaring + loud tire noise started coming on. Noise is totally gone now!
 

tokahao

Member
Dec 9, 2011
79
DenaliHD66 said:
[SOLVED]

Had front wheel bearings and CV Half shafts replaced. Assuming it was the bearing because this noise started first, then the roaring + loud tire noise started coming on. Noise is totally gone now!

Darn. I'm having a similar problem but I don't think your solution will solve mine. The sound I'm hearing reminds me of a pepper shaker (shick shick shick shick shick) under the Voy, I only hear it when I'm coasting. If I push the shifter into neutral while it's happening it stops all together... something with the engine and trans? Super glad you got your prob figured out. How much it run you?
 

RZAwora

Member
Apr 15, 2012
196
tokahao said:
Darn. I'm having a similar problem but I don't think your solution will solve mine. The sound I'm hearing reminds me of a pepper shaker (shick shick shick shick shick) under the Voy, I only hear it when I'm coasting. If I push the shifter into neutral while it's happening it stops all together... something with the engine and trans? Super glad you got your prob figured out. How much it run you?

I have an '06 with the V8 that makes a similar noise. It's not very loud, but yet apparent. I think it may be the same sound you're referring to here. From all my reading I determined that it is the DOD (displacement on demand) in operation that makes that noise. This is when the engine shuts down cylinders due to not having a load on the engine. It will stop if you (a) give it some gas, or (b) put the truck in neutral and continue coasting, or (c) drop it down into 3rd, since all of these actions shut down the DOD. See if that is true with yours too.
 

Denali n DOO

Member
May 22, 2012
5,596
rzawora said:
I have an '06 with the V8 that makes a similar noise. It's not very loud, but yet apparent. I think it may be the same sound you're referring to here. From all my reading I determined that it is the DOD (displacement on demand) in operation that makes that noise. This is when the engine shuts down cylinders due to not having a load on the engine. It will stop if you (a) give it some gas, or (b) put the truck in neutral and continue coasting, or (c) drop it down into 3rd, since all of these actions shut down the DOD. See if that is true with yours too.

Driving in 3rd disables the DOD? So I if I go from park to 3rd and start driving then the DOD will not activate? I never knew that. Wouldn't my gas mileage get worse if that were the case?
 

RZAwora

Member
Apr 15, 2012
196
I'm almost certain it does. I remember reading it on the old site, and also one guy who always drove around town in 3 and put it in D only on the highway. He did this because he couldn't stand the noise. Your gas mileage may suffer from having it in 3 but that would also depend upon what speeds you're going. I don't drive that way, but I do know that if I'm coasting at 10-30 miles an hour and there's something for it to echo off of, I can hear the noise. Give it a little gas, it stops. Shift into neutral, it stops. Shift down to 3rd, it stops. It also stops it self almost as soon as you come to a stop, I think when it downshifts into lowest gear, or disengages gear. I don't know all the specifics of an auto trans to know exactly how they work, nor do I know all the specifics on how or when the DOD works, but it's my understanding that the noise I hear (and the one I think you hear) is caused by the DOD being active. Sometimes I wonder how much the DOD affects gas mileage. I usually get around 16mpg stop and go daily driving. Yesterday I pulled a 240 mile round trip highway driving to Baltimore and did 23mpg. And these figures are calculated and not the ones displayed on the DIC. The ones on the DIC don't have any rhyme or reason IMO, what's displayed always seem a tad bit lower then what I actually got. I know there's a lot of variables there. Maybe someone else can chime in if they think the noise you're hearing is what I'm saying.
 

tokahao

Member
Dec 9, 2011
79
rzawora said:
I have an '06 with the V8 that makes a similar noise. It's not very loud, but yet apparent. I think it may be the same sound you're referring to here. From all my reading I determined that it is the DOD (displacement on demand) in operation that makes that noise. This is when the engine shuts down cylinders due to not having a load on the engine. It will stop if you (a) give it some gas, or (b) put the truck in neutral and continue coasting, or (c) drop it down into 3rd, since all of these actions shut down the DOD. See if that is true with yours too.

I wish it was, mine is the '05 without DOD. Back to the drawing board for me. I'll post a video or sound clip when I have a passenger haha
 

tokahao

Member
Dec 9, 2011
79
tokahao said:
I wish it was, mine is the '05 without DOD. Back to the drawing board for me. I'll post a video or sound clip when I have a passenger haha

I take it back, after some Googling and reviewing my VIN it turns out I have DOD (10th letter from the end is "M"). Cool, had it 5 years and didn't know. Now I'm gonna drive around in 3rd and see how the mileage differs :crazy:
 

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