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Rattling upon acceleration

AussieJLOverland

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From everything I've read & experienced myself with this rattling problem I'm thinking the reason FCA isn't coming up with an easy fix is because it's a combination of several factors.....I'm thinking automatic transmission incorrect gear selection at low speed/revs combined with heat & a bad oem tune to boot. The issue seems to happen more & be much more pronounced when the vehicle is working hard like when 4 wheeling & generating much more heat that maybe the cooling fans can't dissipate effectively. On road it only seems to start happening after a prolonged stint of high speed driving like on a hwy followed by sudden slow driving in a town or city in traffic. High octane fuel does seem to lessen the issue on road but doesn't eliminate it altogether while in offroading situations the high octane fuel doesn't seem to alleviate the issue at all but noticeably the engine fluid temps etc all seem to run higher while slowly navigating trails & climbing in 4wd. It runs so much hotter on the trails I can even smell the heat (if you know what I mean). It also seems to be a much bigger problem or even almost exclusive to the Automatic versions of the JL & could be caused by too high a gear selection for purpose (lugging) which can contribute to the problem as well (try selecting a higher gear than you should for the speed your traveling in a manual & you can pretty much replicate the same rattle). I notice on the trails I have to often manually select the gear I want to use in 4wd because the auto keeps selecting too high a gear for purpose. So it's quite possible they are having difficulty rectifying the issue or are reluctant to rectify it because it's not just 1 issue but a combination of several factors needing more than just 1 fix. $$$$. But in my observations HEAT appears to be a factor in its severity.
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SuperNerdEE

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From everything I've read & experienced myself with this rattling problem I'm thinking the reason FCA isn't coming up with an easy fix is because it's a combination of several factors.....I'm thinking automatic transmission incorrect gear selection at low speed/revs combined with heat & a bad oem tune to boot. The issue seems to happen more & be much more pronounced when the vehicle is working hard like when 4 wheeling & generating much more heat that maybe the cooling fans can't dissipate effectively. On road it only seems to start happening after a prolonged stint of high speed driving like on a hwy followed by sudden slow driving in a town or city in traffic. High octane fuel does seem to lessen the issue on road but doesn't eliminate it altogether while in offroading situations the high octane fuel doesn't seem to alleviate the issue at all but noticeably the engine fluid temps etc all seem to run higher while slowly navigating trails & climbing in 4wd. It runs so much hotter on the trails I can even smell the heat (if you know what I mean). It also seems to be a much bigger problem or even almost exclusive to the Automatic versions of the JL & could be caused by too high a gear selection for purpose (lugging) which can contribute to the problem as well (try selecting a higher gear than you should for the speed your traveling in a manual & you can pretty much replicate the same rattle). I notice on the trails I have to often manually select the gear I want to use in 4wd because the auto keeps selecting too high a gear for purpose. So it's quite possible they are having difficulty rectifying the issue or are reluctant to rectify it because it's not just 1 issue but a combination of several factors needing more than just 1 fix. $$$$. But in my observations HEAT appears to be a factor in its severity.
I agree with much of what you're saying. But IIRC folks have been able to fix it with tune... so... if a richer tune can fix the issue, why wouldn't FCA just do that?
 

L06An_5

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Picked up my 21' Willys in March and as the summer kicked in, doors off, I heard what I called an occasional valve tapping. Took it in last week and they said no codes and they didn't hear anything. After listening to the audio here it is the same rattling/tapping noise. I'll try some of the band-aids here but I agree this deserves acknowledgement by FCA.
 

Rodeoflyer

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Village Idiot

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It is engine knock. Probably harmless, and usually at lower rpms with partial throttle input. My brother has it on his pentastar Grand Cherokee also. It may lessen with higher octane, but doesn't go away completely.
 

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BullMoose1776

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I thought in my 2019 3.6 the noise was a heat shield. It happens when the motor is warmed up, and when I have someone press the accelerator, as I am under the hood, I can hear the rattle.



I'm gonna try a few tanks of Shell 93 octane and see what happens.
 

SuperNerdEE

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It is engine knock. Probably harmless, and usually at lower rpms with partial throttle input. My brother has it on his pentastar Grand Cherokee also. It may lessen with higher octane, but doesn't go away completely.
Is engine knock really harmless? My understanding is predetonation is not good for an engine. You want the detonation to occur at just the right instant for proper transfer of power right?
 

BullMoose1776

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I've been running Shell 93 octane for 2 months, and if anything it's worsening. I'm taking it on for the 30k mile maintenance, ideally this week, and I'll have em check it out.
 

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AussieJLOverland

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Took my 2019 JLU in for it's 36,000klm service yesterday & told the dealer about the issue. The dealer said there was an ecu update available which they did which they think may fix the issue. They told me to monitor it & report back if the issue continues. I'll let you know if it still rattles after driving it a bit. I think an earlier commenter said they had an ecu update done by the dealer which didn't rectify anything so I won't hold my breath.
 

AU_JLU

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Took my 2019 JLU in for it's 36,000klm service yesterday & told the dealer about the issue. The dealer said there was an ecu update available which they did which they think may fix the issue. They told me to monitor it & report back if the issue continues. I'll let you know if it still rattles after driving it a bit. I think an earlier commenter said they had an ecu update done by the dealer which didn't rectify anything so I won't hold my breath.
Which dealer in aus did you go to? My dealer backflipped and is trying to claim it’s normal. Please update if it fixed your pinging.
 

AU_JLU

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Update# As expected the recent ecu update the dealer did during the last service did not rectify the rattling issue.
Thanks for reporting back, I really had my fingers crossed. I know a 3rd party tune will fix it. But the dealer has told me they can tell if the car ecu has been tuned and will void my warranty. Even getting a second ecu to place back in for service is easily identified as the software logs time out of the car or something like that, according to Jeep.
 

MikeWelin

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Well y’all can add me to the list , just purchased my 2021 wrangler willys 6 speed last month & with just about 2500 miles on it now, the annoying low grumble rattling upon acceleration sound has begun. sucks that this thread’s been around for years now and still no fix.
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