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Discussion Starter · #1 ·
Pardon me for asking a basic automotive question. My JK has the 5 speed auto, which, as I understood the owner's manual, included overdrive in the highest gear. To me, that means that one should experience much lower rpm's when letting off the gas peddle in that gear and provide a sense of almost 'free wheeling'. That's not the case in my Jeep. I can definitely feel the engine slowing the speed when letting off the gas and the rev's remain fairly high. My milage reflects such a situation in that my overall milage is down around 15. When I first picked her up from the dealer I was getting about 18 city and 21 hwy.

I'm wondering if something has gone wrong in the tranny ? BTW, yes, I have the 4.10 rear axle.., but I would think milage should get better after the first 1000 miles... I now have about 1700.
 

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I have the same setup. 2012 auto jku Rubicon with 4.10. Mileage is about 16 city and 17/18 hwy. Mine has been this way since day one and im at 3500 miles roughly. My motor has the same engine brake when I lay off in which it should.
 

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Discussion Starter · #3 ·
Thanks Jim. I guess it's OK then but the milage sure seems to have dropped way off and I thought OD would free wheel more than it does. Coming from a Suby Outback I'm feeling the pain at the pump..:confused:
 

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I have the same setup. 2012 auto jku Rubicon with 4.10. Mileage is about 16 city and 17/18 hwy. Mine has been this way since day one and im at 3500 miles roughly. My motor has the same engine brake when I lay off in which it should.
. If you shift up or down manually, doesn't it display what gear you are in?
 

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:whistling: Interesting, my '08 JKUR gets that kinda mileage when I'm on fairly level freeway (17/18)-

I just got (math) 15.2 mpg going from 4200 ft/7000ft/sea level ft-224 miles-

I've got 5.38 gears !

:dance::rofl: JIMBO
 

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Your mileage is pretty much where it will be. Although I have an 09, my mileage is in the mid-teens overall but I was happy to get 20 going the 300 miles to Vegas the other day. We have winterblend fuel right now so that contributes to the lower figures as well. I wouldn't mind having a Suburu either but the real cost difference between 17 and 20 or 22 average is really not that much. The numbers just sound more significant. The $70 per month difference is not going to get me to buy a different vehicle.
 

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You need a 11 model 4 speed auto. Way more rmp drop then the 12 models have. Like .69 in the 11 and .82 in the 12. Overdrive gear ratios.
 

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Yes if u use the autostick it does display the gear. In the auto, at any speed if I lay off the throttle my motor begins to slow but as the OP said, rpms remain high wasting gas. Saves my brakes but kills mpgs
 

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Discussion Starter · #9 ·
Yes, using auto stick displays the gears, the OD off lite is not lit and I dunno how to turn off OD anyway..nor do I want to. I'm wondering if there is anything a dlr can do to change this...doubtful. I had heard of re-flashing but I think that just changes shift points. Like I said, I dunno much about mechanics.
 

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Yes, using auto stick displays the gears, the OD off lite is not lit and I dunno how to turn off OD anyway..nor do I want to. I'm wondering if there is anything a dlr can do to change this...doubtful. I had heard of re-flashing but I think that just changes shift points. Like I said, I dunno much about mechanics.
To turn overdrive off on the new FANGLED 5 speed auto all u have to do is shift it to 4th gear and it will not upshift to 5 or overdrive on it's own. I don't think you have any OD off button as you have complete control with the select shift stick. I am not sure but I think 4th gear is direct, or 1 to 1 ratio.
 

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They changed the fuel mapping for the Pentastar Jesus Motor and now when you are coasting in any forward gear the fuel is shut off completely untill the engine gets down to 1000rpms. This saves gas but slows the vehicle quicker than when engines receive an idle quanty of fuel when coasting.
 

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Also, in a modern automatic transmission when you let off the throttle the rpms won't drop b/c you have a locked torque converter. So the rpms stay exactly where they where when you where on the throttle just as if you where driving a stick.
 

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Discussion Starter · #13 ·
OK...a related question. Eco mode ? the small rubber button under the speedo where you can change to trip odometers has one function called Eco...as you drive and let off the gas it will go from Eco off to Eco and vice versa. I can't tell if it's free wheeling any more or just telling you when you're rev's are going up/burning gas. Only found it the other day. OM does not explain it well.
 

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They changed the fuel mapping for the Pentastar Jesus Motor and now when you are coasting in any forward gear the fuel is shut off completely until the engine gets down to 1000rpms. This saves gas but slows the vehicle quicker than when engines receive an idle quantity of fuel when coasting.
Do you know if this is true if while coasting you downshift?

:D

DB
 
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