Some gearing questions
02-22-2009, 09:01 PM
#12
JK Freak
my 2 dr auto Sahara came with 4:10's. when I went to 35's I did not like the on road or off road power. I regeared to 4:88's and my speedo is off by about 10%. The trip computer is showing 12.5 mpg so if I add 10% it would be around 13.75. I drive it pretty hard and not too much on the freeway. The power difference was great. I would have gone to 5:13's if I wanted 37 inch tires. the 5:13 gear set is not as strong as the 4:88 ring and pinion though.
02-22-2009, 09:08 PM
#13
JK Super Freak
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my 2 dr auto Sahara came with 4:10's. when I went to 35's I did not like the on road or off road power. I regeared to 4:88's and my speedo is off by about 10%. The trip computer is showing 12.5 mpg so if I add 10% it would be around 13.75. I drive it pretty hard and not too much on the freeway. The power difference was great. I would have gone to 5:13's if I wanted 37 inch tires. the 5:13 gear set is not as strong as the 4:88 ring and pinion though.
Thanks again for helping with the endless stream of questions guys, you all rock!
02-22-2009, 09:25 PM
#15
JK Freak
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i have a 4 door rubicon, automatic. just lifted and running 35 bfgkm2's. with the stock 4.10's i am only off 5-6 mph on my speedo according to my gps. didn't think to check mpg, i will next time i drive it.
i notice a small difference in power but not as bad as i expected. i am probably going to go 4.56's when i regear, just to maintain the lower rpm
's at highway speeds.
i notice a small difference in power but not as bad as i expected. i am probably going to go 4.56's when i regear, just to maintain the lower rpm
's at highway speeds.
Just wanted to mention something !!!! You have 4.10 and 35 and if you go to 4.56 and 35 you will actually RAISE the RPM at Highway speed....... It will get you off the line quicker but will lower your overall hiway MPG !!!
Hope this helps ......
I am in the same boat ....... I have 4.10 and 33 and @ 70 mph .... I run 2600 rpm ( the sweet efficient spot for the 3.8 is 2100 rpm ) to accomplish this I need to go to 35 or 37 to slow the revs of the engine to the 2100 or 2200 area !!! But you will lose your take off power by doing so !!!! I have combated this deliemma by adding a supercharger to raise Horsepower at all RPM's
So presently ( til tire change ) I have to run 63 mph to achieve the desired 2200 rpm and I get excellent economy ...... But I HATE driving slow
EDIT""""""""" Just to clarify .... I have the 6-speed Manual Trans """"""""""""""""""""""""""EDIT
Last edited by HULKGREEN; 02-22-2009 at 09:29 PM.
02-22-2009, 09:31 PM
#16
JK Super Freak
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Just wanted to mention something !!!! You have 4.10 and 35 and if you go to 4.56 and 35 you will actually RAISE the RPM at Highway speed....... It will get you off the line quicker but will lower your overall hiway MPG !!!
Hope this helps ......
I am in the same boat ....... I have 4.10 and 33 and @ 70 mph .... I run 2600 rpm ( the sweet efficient spot for the 3.8 is 2100 rpm ) to accomplish this I need to go to 35 or 37 to slow the revs of the engine to the 2100 or 2200 area !!! But you will lose your take off power by doing so !!!! I have combated this deliemma by adding a supercharger to raise Horsepower at all RPM's
So presently ( til tire change ) I have to run 63 mph to achieve the desired 2200 rpm and I get excellent economy ...... But I HATE driving slow
EDIT""""""""" Just to clarify .... I have the 6-speed Manual Trans """"""""""""""""""""""""""EDIT
Hope this helps ......
I am in the same boat ....... I have 4.10 and 33 and @ 70 mph .... I run 2600 rpm ( the sweet efficient spot for the 3.8 is 2100 rpm ) to accomplish this I need to go to 35 or 37 to slow the revs of the engine to the 2100 or 2200 area !!! But you will lose your take off power by doing so !!!! I have combated this deliemma by adding a supercharger to raise Horsepower at all RPM's
So presently ( til tire change ) I have to run 63 mph to achieve the desired 2200 rpm and I get excellent economy ...... But I HATE driving slow
EDIT""""""""" Just to clarify .... I have the 6-speed Manual Trans """"""""""""""""""""""""""EDIT
02-22-2009, 09:53 PM
#17
JK Freak
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you really should go with 5:13's with the auto, I would bet 80-90% of the guys on here that have regeared with 35's and auto have 5:13's and are very happy with them. I know I love mine and I definitely dont think I would have been happy with 4.88. At 70-75 I am running 2500-2700rpm and my speedo is corrected with the hypertech and verified by my gps.
I cant tell you what my actual mpg are because I never bother to figure it out, the dash mpg is definitely not accurate as many have said here, but to give yuo an idea mine usually says between 14-15.5 mpg and I have bit of a heavy foot and I do have 4dr, your 2dr probably will get better mpg....but it is a Jeep, never made for good gas mileage
its made for this though
I cant tell you what my actual mpg are because I never bother to figure it out, the dash mpg is definitely not accurate as many have said here, but to give yuo an idea mine usually says between 14-15.5 mpg and I have bit of a heavy foot and I do have 4dr, your 2dr probably will get better mpg....but it is a Jeep, never made for good gas mileage
its made for this though