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  #13  
Old 04-17-2012, 09:51 PM
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Re: Pentastar vibration at 2000 rpm/60 mph

I've a 2012 Limited 3.6, 500 mi. I get the pulsation (the rpms stay steady) as you mention right around 60 on slight or moderate grades as well, that increases in frequency up through 70. I've had it checked by the dealer who while unable to reproduce it, claims it's torque converter lockup, and it's a design characteristic of the vehicle due to gas mileage compromises, etc. There were no outstanding TSBs for my vehicle nor was it throwing any error codes. It was also described as related to 'ECO' mode, and going heavy on the accelerator and getting the car out of ECO mode should alleviate the problem - however, this didn't work - the problem occurs when I'm heavy on the throttle as well. I'm also rejecting the description that this occurs when I put the vehicle in a specific 'condition'; driving up a normal hill on the highway at nominal highway speeds isn't what I consider a 'condition' (I'm not exactly hammering the vehicle up Pike's Peak in a road rally. I've also read that under mountain driving conditions you should employ tow/haul mode (alas, I don't have that button/package)).

I believe this might also be described as on the forum as transmission shudder, but could be wrong on this, as I've not been in another GC other than the one I have.

Whatever the cause - on a 40K$ vehicle, with 290hp - this should not be happening - no engineering team would possibly foist this sort of design/compromise on the public.

There is at least one TSB for 2011 models for 'transmission shudder' requiring a software update that I've read varying reports in the forum here that ameliorates the problem, but doesn't resolutely solve it. The TSB is not applicable to my vehicle - I'm guessing my build date includes the updated software. Poking around the internet there's a lot of data that is being processed by the whole drive train system (pedal pressure, temperature, etc) so I'd imagine it's not quite so easy to get the software right for this given the electronic and mechanical components. Easy or not, it needs to be fixed.
This link ( http://www.wk2jeeps.com/wk2_transm.htm) is interesting about the transmissions in general (including the upcoming 8 speed tranmission that is described as fitting in the existing housing, so that may be the ultimate solution).


In any event - I'll be pursuing this issue pretty aggressively and will be having a drive with the technicians to demonstrate exactly how to reproduce the issue and ensure that they can reproduce it as well. We'll see if they start replacing drivetrain components.

Good luck to us all.
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Old 04-18-2012, 08:01 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

I don't think its a transmission issue. To me it feels like the VVT system is searching for the right position.
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Old 04-18-2012, 08:26 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

and mine is not a solid vibration...its like a pulsating vibration..only happens at 60 mph 2000rpm..havent felt it at any other time...im thinking its just a normal thing with the engine..
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Old 04-18-2012, 08:32 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

It depends on what the definition of "normal" is. I don't think it causes any harm to the engine, and it's only a minor pulsation, but it's certainly not desirable.
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Old 04-18-2012, 08:41 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

If the engine RPMs are steady, and there's a pulsation - it must be some other mechanical component. Also interesting is that it only occurs on inclines. One theory is it's the torque converter engaging and disengaging - unable to properly handle all of the inputs so it "pulses" back and forth. Drive any other vehicle in the price range - and then re-ask if this is "normal". It's not. Jeep/Chrysler will only address this if their attention is brought to this.
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Old 04-18-2012, 09:13 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

Quote:
Originally Posted by tedt_00 View Post
If the engine RPMs are steady, and there's a pulsation - it must be some other mechanical component. ...
The VVT system (part of the engine) isn't static at a given rpm. Valve timing is changed in response to several factors, including load.

The transmission and components (developed by Mercedes) are used on many other models with different engines. I'm not aware of complaints about those.
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Old 04-18-2012, 09:38 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

Well I just emailed Jeep to notify them of the problem. If enough people do so maybe they'll take it seriously.

http://www.jeep.com/webselfservice/j...m%28%27R%27%29
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Old 04-19-2012, 06:07 PM
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Re: Pentastar vibration at 2000 rpm/60 mph

I have the exact symptoms described by the OP - some type of harmonic noise when the RPMs are 2000-2400 going about sixty and under a moderate load (but not enough to shift the transmission down a gear). It's definately rhythmic and slow. I will report the issue using the link above. I've had the issue since new (early Feb) and still have it at 2200 miles. Glad to see it's somewhat common. Mine is the Limited with 18" Michelins and agree it's not related to the tires as the rpms & throttle position matter need to be as described above to make it occur.
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Old 04-19-2012, 06:43 PM
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Re: Pentastar vibration at 2000 rpm/60 mph

I have it too. I thought it was the full time 4 x 4 hunting uphill or something... Never thought it was the engine.
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Old 04-19-2012, 07:18 PM
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Re: Pentastar vibration at 2000 rpm/60 mph

I have 20" Goodyears- so it's definitely not tires. "Harmonic". That's an excellent description.
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Old 04-19-2012, 08:51 PM
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Re: Pentastar vibration at 2000 rpm/60 mph

Really starting to think its just the way it is with everyone chiming in they have it. And I wonder if the ones that dont just don't notice it. It really doesn't bother me as log as it is not something that can cause damage...
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Old 04-20-2012, 06:34 AM
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Re: Pentastar vibration at 2000 rpm/60 mph

i have a similar noise,if you think it is the tire try putting on the spare it should be a 18" kumo.i'm going on over 1 month in for the same repair it was not there when we bought it but started slowly until now you can here it over the radio at times.it is almost like wetting your finger and running it around the rim of a whine glass a roational sound.we are trying a large dealer who sells several other imports like audi and mercedes.
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