3.73 with 35's on a 2012
JK Freak
Joined: Jun 2011
Posts: 598
Likes: 1
From: Little Rock
Now that is interesting. Hell 1/4 of the guys with 35's run 4.88 gears...if not more. Its crazy that 4.88's with 37's are overgeared....
JK Newbie
Joined: Nov 2011
Posts: 28
Likes: 0
From: Oceanport, NJ
Not to focus on my situation... But why am I getting 11-12 MPG with a 2012 auto 3.73 gears and 35" trail grapplers? Seems like when I'm driving on the highway, it has NO power in 5th gear and have to shift there manually. even still, it wants to go back into 4th. Id assume that's what's killing my MPG? Please help!!! :@
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
Not to focus on my situation... But why am I getting 11-12 MPG with a 2012 auto 3.73 gears and 35" trail grapplers? Seems like when I'm driving on the highway, it has NO power in 5th gear and have to shift there manually. even still, it wants to go back into 4th. Id assume that's what's killing my MPG? Please help!!! :@
JK Newbie
Joined: Nov 2011
Posts: 28
Likes: 0
From: Oceanport, NJ
Originally Posted by JPop
Sounds like you're speedometer isn't calbrated. You definitely need a Procal. Shifts are based on mph and throttle position. Without the speedometer being corrected, you'll get errant shifts and gear hunting. That will rob your mileage and degrade performance.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
Also, if you're using the onboard computer for your mileage, you are rolling significantly more miles than it thinks you are.
JK Enthusiast
Joined: Aug 2010
Posts: 181
Likes: 0
From: Lantana, Texas, United States
Originally Posted by MrDillClinton
Now that is interesting. Hell 1/4 of the guys with 35's run 4.88 gears...if not more. Its crazy that 4.88's with 37's are overgeared....
JK Newbie
Joined: Jun 2011
Posts: 81
Likes: 0
From: Hill Country, TX
To really confuse you...I had 3.73 on my 2012 Unlimited Rubicon, when I went with 35's I also changed to 4.56 gears, which I personally think is the best setup, 4.88 and above would be too steep IMHO and I have an automatic. At the time most people that were going to stay stock gears were running 4.10 on 35's. At 70mph I am running about 2600-2700 rpm and getting 16.5 mpg around town, which is a lot better than my 2010 or 2011 got with 35's...even after Superchips, CAI, and 4.88 gears they at best were getting 13-14 and that was on the highway.
JK Enthusiast
Joined: Aug 2010
Posts: 181
Likes: 0
From: Lantana, Texas, United States
Originally Posted by JKTXJL
How would you compare your power now(4.56 w /35's) to a stock JKU with 3.73 gearing? similar power?
JK Newbie
Joined: Jun 2011
Posts: 81
Likes: 0
From: Hill Country, TX
I would say it has more power on take off and a little quicker on acceleration, but the 3.73 was a little smoother with the lower RPM cruising down the highway at 70, but the 4.56 with 35's has no problems running down the highway at 70 or 80, you are just running a little higher rpm...I have no regrets!
JK Newbie
Joined: Feb 2012
Posts: 6
Likes: 0
From: Muscle shoals, al
Its shift point mapping has nothing to with mph at all. its mapping table is based on rpm, throttle position, load, and traction. the tcm is made to 'learn' if you are having lazy shifts it is because of the way you have been driving it. you need to pull the esp fuse or battery cable for it to reset. you can also use a starscan to reset adaptives. or once diablo cracks the code they will have minor adjuments for the tcm like shift points, firmer shifts, and easy reset for the adaptives.
also i'm getting around 17 mpg (calculated based on the 17% difference in mileage) with mixed driving with the trail grappler.