Gear Ratio vs MPG

Are you running a SYE, cv driveshaft, adjustable control arms?
Nope nope and nope. Every TJ is different but this is lift designed to ideally not need all of that. With the 3 inch lift and 1 inch motor mount it helps the drive line angle to reduce the chance of vibes. Other can provide more details I suspect, reading and research in the forums is what lead me to it, price too. I am not rock crawling, just mild trails, beach (no near the salt water) and wanted to run 33 comfortable on a reasonable budget.
 
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I run 5.38 with 35's and 4-speed automatic like yours and wish the highway rpms were a tad higher.

35" MTR
42rle/33.875"/4.56=2341rpm @ 75mph
42rle/33.875"/4.88=2505rpm @ 75mph
42rle/33.875"/5.13=2633rpm @ 75mph
42rle/33.875"/5.38=2762rpm @ 75mph
42rle/33.875"/5.89=3023rpm @ 75mph
 
i did this, bigger tires, bigger tires. If you are talking highway mileage, there is no magic pill. Bigger tires you can drop a gear or regear. Flat out bigger tires mean more mass to rotate. Regearing will mean you can use 5th or 6th gear more often but gas mileage is a function of resistance to rotate.

Having done 35s on a TJR..... gas mleage will suck regardless of the regearing. I drove an '87 YJ with the 258 and a carb on 33s with the dreaded 3.07s. I never used 5th gear on the highway but it got 25mpg on the highway in 4th gear.

After doing 35s, I quickly went back to 33x10.50s, loved them. On a daily driver 33s are fabulous tires. Then I went a different route, I almost wanted an SE in the mountains and forests where I live but a 4.0L is a nice engine. I wanted a skinnier TJ. I bought 7.50R16s, kinda old school, I had these on my 1977 F250 on split rims new from Ford. Much lighter tires, I went from a best of 17mpg with 33x10.50R15s to 22mpg. I'll never go back. That skinny 7.50 is a fabulous winter tire slicing thru slush and standing water.

IF fuel economy and range count..... I added 95 miles to my range between fills. I know, few of us care but for me an extra 95miles between gas stations open exploring without carrying a jerry can. All done by picking a skinny 31" tall tire.



ps, go here

http://www.grimmjeeper.com/gears.html
DSC_0013.jpeg



I ran 33s on my TJR for years, averaging 25K miles a year, thru 3 sets of 33s. I run lots of highway miles towing 2K pounds in the mountains, my TJR came with 4.10s, I still wish I had 3.73s. I now run 31s and really wish I had 3.73s.

Loaded for work tomorrow, looking at 200 miles over 2 mountain passes towing a trailer.

Honestly, the TJR is the best vehicle I have ever owned.

IMG_0442.jpeg
 
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i did this, bigger tires, bigger tires. If you are talking highway mileage, there is no magic pill. Bigger tires you can drop a gear or regear. Flat out bigger tires mean more mass to rotate. Regearing will mean you can use 5th or 6th gear more often but gas mileage is a function of resistance to rotate.

Having done 35s on a TJR..... gas mleage will suck regardless of the regearing. I drove an '87 YJ with the 258 and a carb on 33s with the dreaded 3.07s. I never used 5th gear on the highway but it got 25mpg on the highway in 4th gear.

After doing 35s, I quickly went back to 33x10.50s, loved them. On a daily driver 33s are fabulous tires. Then I went a different route, I almost wanted an SE in the mountains and forests where I live but a 4.0L is a nice engine. I wanted a skinnier TJ. I bought 7.50R16s, kinda old school, I had these on my 1977 F250 on split rims new from Ford. Much lighter tires, I went from a best of 17mpg with 33x10.50R15s to 22mpg. I'll never go back. That skinny 7.50 is a fabulous winter tire slicing thru slush and standing water.

IF fuel economy and range count..... I added 95 miles to my range between fills. I know, few of us care but for me an extra 95miles between gas stations open exploring without carrying a jerry can. All done by picking a skinny 31" tall tire.



ps, go here

http://www.grimmjeeper.com/gears.html
View attachment 197533


I ran 33s on my TJR for years, averaging 25K miles a year, thru 3 sets of 33s. I run lots of highway miles towing 2K pounds in the mountains, my TJR came with 4.10s, I still wish I had 3.73s. I now run 31s and really wish I had 3.73s.

Loaded for work tomorrow, looking at 200 miles over 2 mountain passes towing a trailer.

Honestly, the TJR is the best vehicle I have ever owned.

View attachment 197539
Thanks. I have seen the gear ratio calculator and found it very useful. That impact orange looks nice!
 
LJR 285/75/16 and stock 4.10s. runs just above 2500 rpms in 6th. Best mpg was 17.7 mpg at 68. Get around 16 mpg at 70-75. Around town is usually 14 mpg. Focus on weight and tire width. Sprung and un-sprung. Stock wheels are a lot lighter then the steel aftermarkets. Not much we can do about aerodynamics.
 
If anyone is interested, i can drive a Jeep that has been half regwared and note the results.
Rear is 4.56 and front still has 3.07.
Gonna pick a rout, a good mix of highway and in town... say 200 miles on rear axle and 200 back on front.
Put this mpg pissing theories to an end, once and for all.
 
What re-gearing does is increase torque at the wheels throughout your operating range. It also reduces your operating range, but on a Wrangler that's not an issue. You're not going to be doing any 150 mph runs at the salt flats anyway.

At certain speeds it can easily increase your MPG. Like say you go from 3.73 to 4.88, there's some range of speed where before you were sitting in 4th and couldn't really use 5th (on a manual) but now you can cruise along in 5th. Which is a better match between your engine RPM and tire size for that speed, resulting in better MPG than you got before, even though it's putting down more power.

I used to own a C5 Corvette. V8 in a fairly light car. I heard "that thing must get horrible gas mileage" a lot. It actually got 30mpg cruising at 70mph. It's light, aerodynamic, and geared for high speed. That equals good gas mileage no matter how overpowered the engine is.
 
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35" MTR
42rle/33.875"/4.56=2341rpm @ 75mph
42rle/33.875"/4.88=2505rpm @ 75mph
42rle/33.875"/5.13=2633rpm @ 75mph
42rle/33.875"/5.38=2762rpm @ 75mph
42rle/33.875"/5.89=3023rpm @ 75mph
2004 LJ 3.73 - 33x10.5 42rle
Well maybe I missed it ... but what is the best RPMs for the best MPG
I really like to commute 120miles to work round trip at least once a week....
 
2004 LJ 3.73 - 33x10.5 42rle
Well maybe I missed it ... but what is the best RPMs for the best MPG
I really like to commute 120miles to work round trip at least once a week....
Best mpg to save $$$ would take a LONG time to equal the cost of a regearing but if I had 33" tires I'd go for no less than 5.13 but personally I'd go 5.38. I have 5.38 with my 35's but even its rpms are lower than I'd prefer. I have always believed that the 5.38 gearing I currently have would be excellent for 33's with the 42RLE transmission.

My highway mpg did go up well over 2.5 mpg by regearing from 4.88 to 5.38 with my 35's and 42RLE, from sub-12 mpg and never seeing 13 mpg to 14.6 during my first long trip.
 
Best mpg to save $$$ would take a LONG time to equal the cost of a regearing
Yep totally agree...
I always remind myself it is not an investment...... is a hobby that makes me happy,

The thing is when I go to Mexico trail you need those extra miles per gallon, there is not that many gas stations.

Thanks Jerry, with your answer and all the reading I've done I'll go ahead and look for those 5.13's
Revolution gears delivery time is until January what do you think about Motive Gear ?
 
2004 LJ 3.73 - 33x10.5 42rle
Well maybe I missed it ... but what is the best RPMs for the best MPG
I really like to commute 120miles to work round trip at least once a week....

If you're anywhere between the torque and power peaks you'll get about the best MPG you're going to get. I don't like the on/off feeling of throttle response trying to cruise way too high, but I don't shoot for the bottom of the range either so I have some power margin before having to downshift. 3k-3200 at 75 is a nice spot to me.