Pre-2012 JK regear question

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Ibjeepin2

New member
So I regeared my 2010 jk 3.8 auto with 3.73s to 4.56s today-Was told I did not need to program the pcm by the shop to account for the new 4.56 ratio gears- I’m still getting some saying it needs done and some saying if it’s a model prior to 2012 there is no need to do so. I just don’t want to tear up my engine or trans due to rpms/shifting issues. I just got it back today from the shop and haven’t really had a chance to test it out fully yet. Seems like it runs fine, per gps speedo, appears to be correct as I previously flashed for the 33 inch tires. Was windy today, so not sure about the shift points and if Thr downshifting issue has gone away. Anymore feedback is always welcome. anyone else on here have the regear done and yours is a older pre-2012 year? Any of you out there that has actually done this...does the axle/gear profile need updated? Thank you all.



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Ibjeepin2 said:
So I regeared my 2010 jk 3.8 auto with 3.73s to 4.56s today-Was told I did not need to program the pcm by the shop to account for the new 4.56 ratio gears- I’m still getting some saying it needs done and some saying if it’s a model prior to 2012 there is no need to do so. I just don’t want to tear up my engine or trans due to rpms/shifting issues. I just got it back today from the shop and haven’t really had a chance to test it out fully yet. Seems like it runs fine, per gps speedo, appears to be correct as I previously flashed for the 33 inch tires. Was windy today, so not sure about the shift points and if Thr downshifting issue has gone away. Anymore feedback is always welcome. anyone else on here have the regear done and yours is a older pre-2012 year? Any of you out there that has actually done this...does the axle/gear profile need updated? Thank you all.



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If there is a 4.56 option on your programmer I would say yes. Why not?
 
automatic, yes

manual, no but speedo will be off

If it's a daily driver I'd do it to get the speedo correct especially for school zones, those damn tickets are expensive and they don't care if you tell them your speedo is off :doh:
 
Update: This is the information I’ve been looking for and appreciate all the input and feedback. I double checked my programmer (JScan) to ensure proper tire size (285s) 33s actually measuring 32” so that is correct. Before messing with the axle ratio setting I took it for a spin. Previously it would down shift in the slightest headwind or going up the slightest of hills. (Steel bumpers, winch, rock sliders, hardtop, full doors, etc) I had no issue whatsoever ever with the overdrive in the on position! Went up a somewhat steep grade at 45mph without having to push the OD button! No limp mode and my gps app shows correct speed. So I’m assuming the articles I’ve been reading that if the JK is prior to 2012 with an auto 42RLE (which mine is) then a flash to update the ratio isn’t needed in my instance. [emoji108]. Rpms/speed are fine, shifting feels smooth and accurate and no down shifting! I’ll drive as is for now until my gears are broke in and will post updates if I end up trying to do the flash.


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