from 19 to 12 mpg...Is something wrong?
JK Freak
Joined: Apr 2008
Posts: 674
Likes: 1
From: Las Vegas, NV
Much confusion....
This was the comment listed on a couple tow capacity charts I found: "**AHT Trailer Tow Package not available with 3.21 Axle Ratio"
I ordered my build sheet from Jeep to verify before I go with gears...but I'm assuming my (and all) tow packages came with 4.10s.
After looking further, it seems like a few sites suggest that the 3.21s were standard only in the 6sp MT, and all of the 4sp ATs came with 4.10s...
TRANSMISSION: NSG 370—MANUAL, SIX-SPEED OVERDRIVE
Availability…..................................... .................................................. ....................................Std.—All models
Description....................................... ...................................... Synchronized in all forward gears and reverse,
multi-rail shift system with top-mounted shift lever
Clutch............................................ ........................................Hydraulic actuation
Gear Ratios
1st….............................................. .................................................. .................................................. ....... 4.46
2nd….............................................. .................................................. .................................................. ....... 2.61
3rd….............................................. .................................................. .................................................. ....... 1.72
4th….............................................. .................................................. .................................................. ....... 1.25
5th….............................................. .................................................. .................................................. ....... 1.00
6th….............................................. .................................................. .................................................. ........ 0.84
Reverse........................................... .................................................. .................................................. ..... 4.06
Axle Ratio............................................. ................................................3. 21 Std., 4.10 Opt. (Std. on Rubicon)
Overall Top Gear.............................................. .....................................2.69 Std., 3.44 Opt. (Std. on Rubicon)
TRANSMISSION: 42RLE—AUTOMATIC, FOUR-SPEED OVERDRIVE WITH VARIABLE LINE PRESSURE
Availability………………................................ .................................................. ......................................Optional Description....................................... ..............Electronic governor, electronically controlled converter clutch
Gear Ratios
1st….. .................................................. .................................................. .................................................. . 2.84
2nd….............................................. .................................................. .................................................. ....... 1.57
3rd….............................................. .................................................. .................................................. ..........1.0
4th….............................................. .................................................. .................................................. ........ 0.69
Reverse........................................... .................................................. .................................................. ..... 2.21
Axle Ratio............................................. .................................................. .................................................. 4.10
Overall Top Gear.............................................. .................................................. ...................................... 2.83
Availability…..................................... .................................................. ....................................Std.—All models
Description....................................... ...................................... Synchronized in all forward gears and reverse,
multi-rail shift system with top-mounted shift lever
Clutch............................................ ........................................Hydraulic actuation
Gear Ratios
1st….............................................. .................................................. .................................................. ....... 4.46
2nd….............................................. .................................................. .................................................. ....... 2.61
3rd….............................................. .................................................. .................................................. ....... 1.72
4th….............................................. .................................................. .................................................. ....... 1.25
5th….............................................. .................................................. .................................................. ....... 1.00
6th….............................................. .................................................. .................................................. ........ 0.84
Reverse........................................... .................................................. .................................................. ..... 4.06
Axle Ratio............................................. ................................................3. 21 Std., 4.10 Opt. (Std. on Rubicon)
Overall Top Gear.............................................. .....................................2.69 Std., 3.44 Opt. (Std. on Rubicon)
TRANSMISSION: 42RLE—AUTOMATIC, FOUR-SPEED OVERDRIVE WITH VARIABLE LINE PRESSURE
Availability………………................................ .................................................. ......................................Optional Description....................................... ..............Electronic governor, electronically controlled converter clutch
Gear Ratios
1st….. .................................................. .................................................. .................................................. . 2.84
2nd….............................................. .................................................. .................................................. ....... 1.57
3rd….............................................. .................................................. .................................................. ..........1.0
4th….............................................. .................................................. .................................................. ........ 0.69
Reverse........................................... .................................................. .................................................. ..... 2.21
Axle Ratio............................................. .................................................. .................................................. 4.10
Overall Top Gear.............................................. .................................................. ...................................... 2.83
Note: When you get to a page, if you hit Ctrl+F (this is find function in Windows), you can search the pages for "ratio" and click through the entire site to find every time the word is used...
Last edited by VEGASSMAN; Mar 22, 2010 at 09:25 AM.
JK Enthusiast
Joined: Oct 2007
Posts: 188
Likes: 0
From: San Diego, CA
In 2007 all automatics got 4.11 gears. My 07 sahara has them. Old rule of thumb was for every inch you go up take off 1 mpg.
With lift and 35s the expect 3 to 4 lower. Have you corrected the speedometer? You will probably improve mileage by taking off od until you can regear.
With lift and 35s the expect 3 to 4 lower. Have you corrected the speedometer? You will probably improve mileage by taking off od until you can regear.
Last edited by Socal Tom; Mar 22, 2010 at 09:53 AM.
Thread Starter
JK Freak
Joined: Nov 2009
Posts: 565
Likes: 2
From: Dublin, CA
As your instruments (Like the ODOMETER and SPEEDOMETER) take the rpm off of the tail shaft, when you regear, (And/or get larger tires, etc...you change the rpm for any given speed, and this makes the miles you thought you drove, and the speed at which you thought you drove them WRONG.
So, its POSSIBLE that you went more miles than the odometer said you did, and, that you were going faster than you thought you were, both of which, or either, will make you hand calculate a loss in mpg.
The dash read out would of course be fictional as well, etc.
Using a programmer, etc...to correct for the gearing and/or tire changes can fix all that of course.
So, its POSSIBLE that you went more miles than the odometer said you did, and, that you were going faster than you thought you were, both of which, or either, will make you hand calculate a loss in mpg.
The dash read out would of course be fictional as well, etc.
Using a programmer, etc...to correct for the gearing and/or tire changes can fix all that of course.
I do have the superchips, and recalibrated for the 35's. I guess I need to start a "5.13 gears fund" !!!
JK Enthusiast
Joined: Jan 2009
Posts: 414
Likes: 0
From: Charlotte, NC
As your instruments (Like the ODOMETER and SPEEDOMETER) take the rpm off of the tail shaft, when you regear, (And/or get larger tires, etc...you change the rpm for any given speed, and this makes the miles you thought you drove, and the speed at which you thought you drove them WRONG.
So, its POSSIBLE that you went more miles than the odometer said you did, and, that you were going faster than you thought you were, both of which, or either, will make you hand calculate a loss in mpg.
The dash read out would of course be fictional as well, etc.
Using a programmer, etc...to correct for the gearing and/or tire changes can fix all that of course.
For example, if you went from 32's to 35's, you dropped your RPM at any given speed by ~ 8.6%
If you went from 3.73's to 5.13's, you INCREASED your RPM at any given speed by ~ 27.3%
The net change in RPM is ~ 18.7% higher RPM at any given speed.
That would make you drive SLOWER than you thought, but drive a shorter distance than you thought as well.
If you were getting, say 14.7 mpg on 32's and 3.73's.....your apparent mpg might GO UP to perhaps 16.3 mpg or so on 35's and 5.13's.
Food for thought.
So, its POSSIBLE that you went more miles than the odometer said you did, and, that you were going faster than you thought you were, both of which, or either, will make you hand calculate a loss in mpg.
The dash read out would of course be fictional as well, etc.
Using a programmer, etc...to correct for the gearing and/or tire changes can fix all that of course.
For example, if you went from 32's to 35's, you dropped your RPM at any given speed by ~ 8.6%
If you went from 3.73's to 5.13's, you INCREASED your RPM at any given speed by ~ 27.3%
The net change in RPM is ~ 18.7% higher RPM at any given speed.
That would make you drive SLOWER than you thought, but drive a shorter distance than you thought as well.
If you were getting, say 14.7 mpg on 32's and 3.73's.....your apparent mpg might GO UP to perhaps 16.3 mpg or so on 35's and 5.13's.
Food for thought.
Thread Starter
JK Freak
Joined: Nov 2009
Posts: 565
Likes: 2
From: Dublin, CA
In 2007 all automatics got 4.11 gears. My 07 sahara bs them. Old rule of thumb was for every inch you go up take off 1 mpg.
With lift and 35s the expect 3 to 4 lower. Have you corrected the speedometer? You will probably improve mileage by taking off od until you can regear.
With lift and 35s the expect 3 to 4 lower. Have you corrected the speedometer? You will probably improve mileage by taking off od until you can regear.
I have been turning the OD off quite a bit. Does it hurt the engine in any form or fashion to run with OD off for an extended period of time? Is it harder on the transmission, or is it actually easier as it is not continuously shifting in and out of OD.
Also sounds like it is a crap shoot to what gears I got on my 09 sahara with towing package.
Thanks for the input all!
Keep em coming!!
JK Freak
Joined: Mar 2008
Posts: 757
Likes: 2
From: Coastal, GA
For an '09 you most likely you have 3.73's. (sorry)
I am pretty sure the 4.10's were only offered in '07 on all but Rubi's
With an auto the 3.8 is struggling on the 35's and burning more gas in
the process.
You are going to have to go to a 4.88 or 5.13 to be satisfied.
I am pretty sure the 4.10's were only offered in '07 on all but Rubi's
With an auto the 3.8 is struggling on the 35's and burning more gas in
the process.
You are going to have to go to a 4.88 or 5.13 to be satisfied.
JK Freak
Joined: Dec 2007
Posts: 752
Likes: 0
From: New York
If you have an AT, then being in the 12's is on the low side, but nothing out of the ordinary.
Few questions:
What size did you input when calibrating your tire size? 35's are rarely ever really 35" tall. Double check your speedo with a GPS. My 35's measured out at about 33.1".
Are you unknowingly driving around with your airconditioner on? If it's set to "Mix" or Defrost, then your A/C kicks in automatically.
Whats your average speed when on the highway? I find that anything over 65mph and I'm burning gas faster than taco bell.
I'm at about a 80% highway 20% local road mix right now and I'm getting 13.5mpg's on my JKU with 35's, armor, lift, kids, etc.
Few questions:
What size did you input when calibrating your tire size? 35's are rarely ever really 35" tall. Double check your speedo with a GPS. My 35's measured out at about 33.1".
Are you unknowingly driving around with your airconditioner on? If it's set to "Mix" or Defrost, then your A/C kicks in automatically.
Whats your average speed when on the highway? I find that anything over 65mph and I'm burning gas faster than taco bell.
I'm at about a 80% highway 20% local road mix right now and I'm getting 13.5mpg's on my JKU with 35's, armor, lift, kids, etc.
JK Freak
Joined: Nov 2009
Posts: 526
Likes: 0
From: Springboro, OH
I have a 2009 Sahara and the 3.73 gears were mandatory when adding the automatic option. You also get the 3.73 gears when adding the tow package. Same is true with the 2010 if you go to jeep .com and build a Wrangler it will force the gear changes. There is no option for 4.10 gears (maybe by special order only, but not an option on the website). I "believe" 2007 was the last year 4.10 gears were an option.
JK Enthusiast
Joined: Oct 2007
Posts: 188
Likes: 0
From: San Diego, CA
Thanks Tom!
I have been turning the OD off quite a bit. Does it hurt the engine in any form or fashion to run with OD off for an extended period of time? Is it harder on the transmission, or is it actually easier as it is not continuously shifting in and out of OD.
Also sounds like it is a crap shoot to what gears I got on my 09 sahara with towing package.
Thanks for the input all!
Keep em coming!!
I have been turning the OD off quite a bit. Does it hurt the engine in any form or fashion to run with OD off for an extended period of time? Is it harder on the transmission, or is it actually easier as it is not continuously shifting in and out of OD.
Also sounds like it is a crap shoot to what gears I got on my 09 sahara with towing package.
Thanks for the input all!
Keep em coming!!
WIth mine I run about 2K rpm at about 65, if you stay south of 3k for normal driving then the engine will be fine. It probably would like to be at about 2500 rpm anyhow.
Tom