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Old 04-08-2012, 07:14 PM
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2011 Grand Cherokee Hum on freeway

I have a 2011 Grand Cherokee Overland, 5.7 Hemi
Does anyone get a strange hum from the engine at freeway speed when the ECO light comes on? Is this normal? I find it annoying but liveable if thats the way it has to be.
I have heard the hum at lower speeds also. I know its running just 4 cylinders when the Eco light comes on but wished I didnt hear that hum. Is there a solution to that?
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Old 04-08-2012, 07:48 PM
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Re: 2011 Grand Cherokee Hum on freeway

The hum is the MDS system kicking in and you're running on 4 cylinders. Its a known hemi issue and unfortunately you have to live with it. There are some other threads here where people have eliminated this by driving with "tow" active, or else shifting manually into 5th--as this apparently keeps the engine from activating the MDS.

The Eco light doesn't actually show when you're on 4 cyls, it only comes on when you're not heavy on the gas pedal.
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Old 04-08-2012, 08:59 PM
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I have a humm in the front end at highway speeds only. There isn't a correlation between the eco light and the humm. The dealer can't figure it out. I don't have time to deal with them right now so I'm going to wait until I get closer to 36k which isn't to far.
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Old 04-09-2012, 12:54 AM
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Re: 2011 Grand Cherokee Hum on freeway

My GC doesn't have any such hum. No matter what speed.
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Old 04-09-2012, 07:46 AM
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Re: 2011 Grand Cherokee Hum on freeway

Happens with the 3.6L as well. Tends to be when coasting in the mid-50s to 65mph only. Also note it during early light acceleration during 1st/2nd gears. Louder outside than inside the car when pulling into my garage.
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Old 04-09-2012, 08:24 AM
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Re: 2011 Grand Cherokee Hum on freeway

Quote:
The Eco light doesn't actually show when you're on 4 cyls, it only comes on when you're not heavy on the gas pedal.
You sure about this? I had an 06 Magnum a few vehicles back and did the MDS light mod (wired a light to the MDS system that lit up when MDS was active) and the ECO indicator on the Jeep behaves exactly like the MDS light on the Magnum.
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Old 04-09-2012, 08:46 AM
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Re: 2011 Grand Cherokee Hum on freeway

OP is likely referring to exhaust drone when MDS 4 cylinder kicks in and back flow changes causing resonance.

You either can turn up the stereo if cruising highway distances, or shift down into 5th to disengage MDS.
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Old 04-10-2012, 12:44 AM
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Red face Re: 2011 Grand Cherokee Hum on freeway

Quote:
Originally Posted by jd2012jgc View Post
The hum is the MDS system kicking in and you're running on 4 cylinders. Its a known hemi issue and unfortunately you have to live with it. There are some other threads here where people have eliminated this by driving with "tow" active, or else shifting manually into 5th--as this apparently keeps the engine from activating the MDS.

The Eco light doesn't actually show when you're on 4 cyls, it only comes on when you're not heavy on the gas pedal.
The FUEL SAVER MODE message will display above the average fuel economy in the EVIC display. This message will appear whenever MDS (if equipped) allows the engine to operate on four cylinders, or if you are driving in a fuel efficient manner.
The manual seems to suggest that the Eco light does come on when its running 4 cylinders or your saving fuel
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Old 04-10-2012, 12:45 AM
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Re: 2011 Grand Cherokee Hum on freeway

Thank you for your reply
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Old 04-10-2012, 12:53 AM
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Re: 2011 Grand Cherokee Hum on freeway

Id like to thank everyone for their replys. I love my Jeep. Its just as nice or nicer than the Lexus I turned in for it. Quiet,smooth and awesome power. Also has alot more goodies in it. I gave the Lexus dealer a chance to match all the options I got on my Jeep to stay with Lexus, but they came up short except on the price, which was quite a bit higher. Anyway Im glad to be part of this community and once again appreciate all your replys. Thanks
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Old 04-11-2012, 05:54 AM
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Re: 2011 Grand Cherokee Hum on freeway

I have that Hum on high speeds also. cycles of about 2 seconds.
Its annoying, I though it is something related to the wind.
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