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Slight vibration felt through gas pedal?

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Slight vibration felt through gas pedal?

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Old 02-11-2009, 11:19 PM
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Default Slight vibration felt through gas pedal?

This is kind of a weird one, but bear with me. When I'm driving in my 09 Ram and just cruising in the low RPM range (basically between 1500 and 2000) I can feel a slight vibration (almost buzzing like sensation) through the gas pedal. Anybody else notice this?

I'm sure it's not something in the gas pedal itself, more likely something from the truck transmitting vibration through the body, which in turn is going through the gas pedal. If you drive with boots or thick soled shoes, you probably wouldn't even feel it.

It's not a vibration like you would have with an unbalanced tire. Imagine more like if somebody took a hand held massager and put under the gas pedal while your foot was on it. That's the best way I'd know to describe it (at least I imagine that's what it would feel like!).

I am just curious to see if anybody else is feeling this. It is only under real light acceleration at low rpm or cruising at a low rpm. Under moderate acceleration or higher rpm I don't feel it.
 
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Old 02-12-2009, 07:29 AM
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The vibration that you are talking about is a harmonic balance issue. I assume you have a hemi because the 4.7 doesn't have the issue.

Mine is VERY annoying from 1100 to 1400 rpm. In city driving the engine stays in this range most of the time especially when slowing and braking. For a long time, I was conerned about the brake system or bearing, but determined that it is the harmonics of my engine. It obviously involves others as well.

My 2002 quad had the 4.7 so I don't know if this has been a problem with the hemi for a long time, but I have driven several over the years and never noticed the problem, but I sure have it in my 09.
 
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Old 02-12-2009, 09:16 AM
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i think i may have it too but i was thinking it was the vibration from the bass in the stereo. gonna have to see if i feel it with the radio off...
 
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Old 02-12-2009, 10:16 AM
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Default Fuel Saver mode

I have been noticing it also. I have concluded that it happens when the fuel saver mode engages. I assume that when the fuel saver message appears in the information screen that this means the engine is only running on 4 cylinders. As soon as I give it a little more throttle, the fuel saver message goes off and the vibration is gone.
 
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Old 02-12-2009, 11:31 AM
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I don't have the indicator in my truck because it was built in before Dec 08, so I can't make an opinion on that possibility. I will however say that anytime my engine is between 1000 rpm and 1500 rpm, you can feel it in your hands, seat of the pants, and pedals. I really don't think mine is MDS. It is most noticeable with the throttle closed and slowing down with the rpms hanging around 1100. Does the MDS come on with the throttle closed and coasting? There really would be nothing to gain. It would actually hurt engine braking.
 
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Old 02-12-2009, 11:39 AM
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I have not noticed it. I will pay attention to it on the way home today.
 
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Old 02-12-2009, 12:02 PM
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The harmonic balance issue Dr. Bill described above is accurate. The reason the Hemi may have a few vibrations that can get past the isolation mounts is because of the MDS. Every engine has a few resonance frequencies that engineers have to specifically tune the engine mounts to isolate and filter out. When you take the same engine and shut down half of its cylinders and turn it into a 4 cylinder motor, you greatly increase the number of resonance frequencies you need to filter out. This made tuning the engine mounts on the Hemi especially difficult. Don't get me wrong, they did a great job because you can barely feel the transition from 4 to 8 cylinders and vice versa. Regardless, you can still feel it. The isolator package they came up with was the best compromise based on all the different modes the system has. In low rpm's I can feel a coarsness in my gas pedal too. Usually MDS is on, but not always. Its normal though. I hope this helps.
 
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Old 02-12-2009, 12:58 PM
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Default MDS on...

Yes the MDS will come on when coasting and slow speeds. My Fuel saver light will come on just traveling 20-25 mph through the subdivision. I'm am usually barely on the throttle (little to no throttle at all really). My subdivision has the speed humps so I am usually just easing up to each hump and the fuel saver light comes on in between these humps....thats also when I notice the vibration and the change in engine sound (ever so slight).
 
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Old 02-12-2009, 01:14 PM
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I really find the buzz annoying. I would really consider turning the MDS off because of it. I would really like to in order to make sure that is it. It does appear to be the leading contender.

I would think that it is a software application. Is there a hand programmer or tuner that allows you to disable or activate at will?
 
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Old 02-12-2009, 04:25 PM
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Originally Posted by Dr. Bill View Post
I really find the buzz annoying. I would really consider turning the MDS off because of it. I would really like to in order to make sure that is it. It does appear to be the leading contender.

I would think that it is a software application. Is there a hand programmer or tuner that allows you to disable or activate at will?
Diablsport said they will not have a tuner for a while. There were quite a few changes made to the PCM for 2009.

Mine does not have a rattle or vibration aside from the one at idle.
 
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