Noise/Vibration in tow/haul and other conditions
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Noise/Vibration in tow/haul and other conditions
'08 Hemi Ram 2500 QC 4x4 with about 4K miles, 265/70/R17E A/T tires.
I was playing with tow/haul/OD in city and noticed that at ~47Mph I picked up a vibration and noise. Below about 45 and above about 50 it went away. It is happening in cruise and under very light acceleration. This also happens with O/D off. Engine about 1700RPM. It takes about 10 seconds after going into tow/haul or OD off before the symptoms appear. The same thing happens if I start in tow/haul (or OD off) and bring my speed up to 47. Everything is stock on the truck (other than, for completeness, a topper and trans temp sender/gauage).
I did a test-ride with a dealer mechanic and he was able to duplicate it. He also noticed it, but not as strongly, about 65Mph (also ~1,700RPM) in direct. He says he felt it in 2nd at about 1,700 as well, but I couldn't feel it.
He hasn't seen this before, but feels that it is probably exhaust harmonics. He's also going to do some surfing/searching to see if he can find anything else.
The vibration is felt mostly in my feet, and the sound is most like a moan/hum.
Any other opinions? Any suggested additional testing? If it's just an exhaust harmonic/vibration, I'm not too worried, but if there is a mechanical issue I'd like to get it taken care of before it becomes ar eal problem.
Thanks,
I was playing with tow/haul/OD in city and noticed that at ~47Mph I picked up a vibration and noise. Below about 45 and above about 50 it went away. It is happening in cruise and under very light acceleration. This also happens with O/D off. Engine about 1700RPM. It takes about 10 seconds after going into tow/haul or OD off before the symptoms appear. The same thing happens if I start in tow/haul (or OD off) and bring my speed up to 47. Everything is stock on the truck (other than, for completeness, a topper and trans temp sender/gauage).
I did a test-ride with a dealer mechanic and he was able to duplicate it. He also noticed it, but not as strongly, about 65Mph (also ~1,700RPM) in direct. He says he felt it in 2nd at about 1,700 as well, but I couldn't feel it.
He hasn't seen this before, but feels that it is probably exhaust harmonics. He's also going to do some surfing/searching to see if he can find anything else.
The vibration is felt mostly in my feet, and the sound is most like a moan/hum.
Any other opinions? Any suggested additional testing? If it's just an exhaust harmonic/vibration, I'm not too worried, but if there is a mechanical issue I'd like to get it taken care of before it becomes ar eal problem.
Thanks,
Moderate User
Joined: Oct 2008
Posts: 17,003
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From: Albany, NY
Well your tow/haul has nothing to do with it and at 47mph your truck is right about where O/D would kick in/out however if it's at a certain rom that this happens, it has nothing to do with either one of those functions. What your describing could be numerous things. I could probably think of about 100 different possibilities. 98.33% sure it has nothing to do with yout tow/haul or O/D functions!
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Joined: Feb 2008
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From: Nashville
I have a similar problem with my 06 but it is between 35-40 and about 1200 rpm. They tightened the heat shield around my muffler and changed the clutch fan. But the noise was still there. Final they told me it would be to hard to pinpoint where the sound was coming from and to just come back when it gets worse or the truck gives a code.
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I did a road test with a Chrysler mechanic a couple of weeks ago, and he thought (didn't sound very sure) that "it might be an exhaust moan". I was supposed to go in over the weekend and road-test an equivalent vehicle for comparison but somebody got their wires crossed and one wasn't available. The service writer setup another road test with their "senior mechanic" for this morning.
When I went in, I explained what was happening and he had an immediate, "yeah, {we} know about that. It's exhaust moan." I chatted a bit with him and apparently he actually called in Chrysler engineers to diagnose the problem on somebody else's vehicle. They used "chassis ears" (electronic stethoscope) and found that it was in the exhaust. Apparently, if you have it, you essentially just ignore it. They tried various things and couldn't get rid of it, including playing with the exhaust.
The 2500 Hemi seems to be more prone to it, but he's seen it in other vehicles as well.
I was able to consistently reproduce it by 47mph, 1700-1800Mph, in tow-haul, and very light load (i.e. slowly accelerate into the speed/rpm). I was more concerned about "is it noise, or is it mechanical". Even though it take a pretty rare set of circumstances to show up, it was one of those things that once you know it is there....
When I went in, I explained what was happening and he had an immediate, "yeah, {we} know about that. It's exhaust moan." I chatted a bit with him and apparently he actually called in Chrysler engineers to diagnose the problem on somebody else's vehicle. They used "chassis ears" (electronic stethoscope) and found that it was in the exhaust. Apparently, if you have it, you essentially just ignore it. They tried various things and couldn't get rid of it, including playing with the exhaust.
The 2500 Hemi seems to be more prone to it, but he's seen it in other vehicles as well.
I was able to consistently reproduce it by 47mph, 1700-1800Mph, in tow-haul, and very light load (i.e. slowly accelerate into the speed/rpm). I was more concerned about "is it noise, or is it mechanical". Even though it take a pretty rare set of circumstances to show up, it was one of those things that once you know it is there....
