Reality Check Needed

[Jeepeto]

I'm looking for some opinions on the numbers from a recent roadtrip and the conditions I was driving in. Went on a 700 mile roadtrip through lower northern Michigan and temps were in the mid-teens and winds were high. At times I could barely keep the Jeep in my lane on the freeway because the gusts were so strong. I'd have the top center of the wheel at 10 or 2, depending on the wind direction, to keep it in the lane.

I'm running the 3.6L (no etorque) on 37s with 4.56s. During the the freeway stretches the Jeep was constantly between shifting between 7 and 8th gear with the occasional dip to 6 if there was more of a grade on 75. The headwind was some of the worse I've driven in. Average mileage for the entire trip was in the low to mid 16s. I'm less concerned with the mileage as I am with the constant shifting of the transmission. Given the weather conditions, is this normal behavior on the 8speed auto, or is it at all worth considering 4.88s?

Wait… you’re getting 16mpg!?

I average ~12.5 with 37s and 4.56s ?

Wind is definitely more of a problem with this rig than the last one on 35s, what your describing sounds about right.

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[Lionel Hutz]

I have 3.45 gears + 2.0T and 37's recalibrated and such on my 2 door. Sounds like the same ride I get in 50-60mph winds. I average 19-20 mpg regularly, but it will dip exactly down to 16 mpg just as you described. If you hadn't posted this I would have never had the energy to detail it how well you did. It does hunt for gears, but I hit 8th gear without much issue. What PSI were you running? Lately it's been so cold I've been running 36 PSI warm. In the Spring and Summer I run 33 PSI warm.

I've been running 37psi

 

[Lionel Hutz]

Wait… you’re getting 16mpg!?

16.2 MPG was the average for the trip. I was pretty surprised with the number. I was more concerned with the constant transmission shifting and hunting for gears.

 

[Lionel Hutz]

Wait… you’re getting 16mpg!?

I average ~12.5 with 37s and 4.56s ?

Wind is definitely more of a problem with this rig than the last one on 35s, what your describing sounds about right.

I drive pretty easy with the skinny pedal. If I put my foot into it a lot that MPG number tanks.

 

[Jeepeto]

16.2 MPG was the average for the trip. I was pretty surprised with the number. I was more concerned with the constant transmission shifting and hunting for gears.

I think I’d go for 5.13s if I ever regeared, but It’s “good enough” with the 4.56s for me. I knew it wouldn’t be perfect, but it came from the factory with a warranty and it still drives great <70-75mph. My wife dailies it around town, and it only really affects me on long road trips

 

[wranglernoob2019]

I'm looking for some opinions on the numbers from a recent roadtrip and the conditions I was driving in. Went on a 700 mile roadtrip through lower northern Michigan and temps were in the mid-teens and winds were high. At times I could barely keep the Jeep in my lane on the freeway because the gusts were so strong. I'd have the top center of the wheel at 10 or 2, depending on the wind direction, to keep it in the lane.

I'm running the 3.6L (no etorque) on 37s with 4.56s. During the the freeway stretches the Jeep was constantly between shifting between 7 and 8th gear with the occasional dip to 6 if there was more of a grade on 75. The headwind was some of the worse I've driven in. Average mileage for the entire trip was in the low to mid 16s. I'm less concerned with the mileage as I am with the constant shifting of the transmission. Given the weather conditions, is this normal behavior on the 8speed auto, or is it at all worth considering 4.88s?

i drove stock rubicon xr 600 miles recently in the same windy / cold conditions last week- same issue and got mileage of 13. You must be
lucky !!

 

[Lionel Hutz]

i drove stock rubicon xr 600 miles recently in the same windy / cold conditions last week- same issue and got mileage of 13. You must be
lucky !!

There were some stretches that were below 60 and even 30 MPH. That certainly helped the MPG average for the trip.

 

[Equitasforall]

I'd love to help, but my reality check bounced a long time ago.

 

[JRMedic19]

@blnewt This new cast iron steering box is interesting and is new information to me. Could you elaborate how you got that and why. Did you have the dealer do the swap as warranty or something?

 

[blnewt]

@blnewt This new cast iron steering box is interesting and is new information to me. Could you elaborate how you got that and why. Did you have the dealer do the swap as warranty or something?

Here's a huge thread on this
https://www.jlwranglerforums.com/fo...ew-steering-gear-box-per-tsb-08-074-20.56822/
And here is the TSB on that
https://static.nhtsa.gov/odi/tsbs/2020/MC-10181634-9999.pdf

 

[Zandcwhite]

37 inch tire with an eight speed automatic transmission needs a 5.13 gear ratio. I suggest you find somebody to test drive with, you’ll love it. 488 is not enough gear. 392 wrangler comes with 456s and 35 inch tires. you need gear or motor. It’s physics its math it’s pretty simple

392 comes with 3.73's and 33's, which is equivalent to a 4.18 gear on 37's. The xr does come with 35's and 4.56's, but even cherry picking the deepest geared model the equivalent gearing is still only 4.82 on 37's. Of course if you go the other direction, a stock willys has 33's and 3.45s, which is equivalent to 4.10's on 39's. It appears even jeep either doesn't know what gearing should go with which tire size with the 8 speed auto or they understand that with a deep 1st gear and an incredibly tall 8th gear that it really doesn't matter how you gear your jeep with this transmission.

 

[Mudduck]

392 comes with 3.73's and 33's, which is equivalent to a 4.18 gear on 37's. The xr does come with 35's and 4.56's, but even cherry picking the deepest geared model the equivalent gearing is still only 4.82 on 37's. Of course if you go the other direction, a stock willys has 33's and 3.45s, which is equivalent to 4.10's on 39's. It appears even jeep either doesn't know what gearing should go with which tire size with the 8 speed auto or they understand that with a deep 1st gear and an incredibly tall 8th gear that it really doesn't matter how you gear your jeep with this transmission.

My Willys has 255/75/17, I think that’s equivalent to 32x10x17.
! Inch makes a big big difference….. ?

 

[bumpit]

easy answer is your under-geared for a 37" tire. I'd be looking to 4.88 and really only would chose 4.56 if I was to never go above a 35. I'm not sure I'd re-gear to 4.88 from 4.56 but that is definitely why you were dropping gears. If you were coming from 4.10 or lower I"d say 4.88 would be worth it but not from 4.56.

 

[omnitonic]

I've got the manual, and I'm running 35s on 4.56 gears. This setup is generally pretty good, but I got into some big winds recently, and I was having to downshift all the way to 4th gear just to keep the thing moving against a stiff headwind. The wind was also blowing me around so badly I kept looking over my shoulder for blue lights, prepared to be sobriety tested. This brick is not exactly nimble in heavy winds.

Since you already have 4.56 gears, I would probably stick with those, but I think 4.88 gears with your 37s would be a closer match to my setup.

 

[DanW]

I'm looking for some opinions on the numbers from a recent roadtrip and the conditions I was driving in. Went on a 700 mile roadtrip through lower northern Michigan and temps were in the mid-teens and winds were high. At times I could barely keep the Jeep in my lane on the freeway because the gusts were so strong. I'd have the top center of the wheel at 10 or 2, depending on the wind direction, to keep it in the lane.

I'm running the 3.6L (no etorque) on 37s with 4.56s. During the the freeway stretches the Jeep was constantly between shifting between 7 and 8th gear with the occasional dip to 6 if there was more of a grade on 75. The headwind was some of the worse I've driven in. Average mileage for the entire trip was in the low to mid 16s. I'm less concerned with the mileage as I am with the constant shifting of the transmission. Given the weather conditions, is this normal behavior on the 8speed auto, or is it at all worth considering 4.88s?

It's normal. First, 7th is still overdrive. My wife's 2021 is stock with 33s and 4.10 and it stays in 7th at 75 on flat ground.

Second, you were in unusually harsh conditions. Very harsh. I wouldn't set it up based on a 1% scenario. I don't think what you would gain would be worth it.

I'm on 35s with 4.56 in my JLUR 6 speed. I love it but at the end of the day not sure I'd spend the money if I had a do over. All it did was help 6th gear. 1st was fine with 4.10 gears. Before the swap I went to Moab and drove into a big head wind across Kansas and western Colorado in 5th and it did fine, requiring 4th only on major hills. It bugged me not to use 6th and that's why I swapped gears. But again, not sure I'd repeat that decision. I have only had that kind of head wind once in 4 years with this Jeep.

Just my 2 cents.

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