Gears for 37" tires

[Ted Striker]

I live just outside of Houston but work in Houston. Been thinking about going to 37’s on my Mojave. What kinda MPG you getting?

15 - hand calculated using Fuelly since day one

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[Toyfrog]

15 - hand calculated using Fuelly since day one

I’m getting about 16.5 on 35’s and stock suspension. Hand calculated with Fuelly also. My drive consists of 225 to 610 to 45 to downtown. No constant speed. Lol. Been thinking about hitting the belt of 99 and seeing what I get at a constant speed?

 

[Muddzy]

Got 5.13s in April, drove 500 miles and changed the gear oil, then drove 4100 miles from NJ to CO and back the past 10 days. I towed a 2,350# 5x8 uhaul enclosed trailer without brakes and the JT weighed 6,920 w/3 passengers and full tank of gas. The trailer towed like it wasn't behind me except I could feel it when there was a strong crosswind or sometimes passing a semi. The braking distance was a little impacted but not by much. Refresher - I have JTR with 37s and 3in lift with accessories including RTT on 1/2 bed rack, 1/2 roof rack over cab, 270deg awning, winch, plus some other accessories.

Avg 10.8 mpg heading to CO and 11.7 coming back so that's a total trip average of 11.2 (hand calculated). Just over $1500 was my fuel bill ? and that was about $450 more than my fuel bill for the same trip in January (I didn't tow a trailer then and averaged 11.9mpg). Just like in January, I was driving an average of about 5 mph over the posted speed limit throughout the trip. I believe 2-3 mpg could be gained if I didn't exceed 65mph vs the 75-80mph I was pushing the brick.

Bottom line is I'm really happy with the 5.13s on both highway and off-road. Shop recommended the 5.13s over the 4.88s and they were right. I was also happy with being able to do 65mph going up the steep, long and high altitude CO passes without the engine close to redline but I can see why others that are consistently towing significantly more weight up the passes might want 5.38s, or better yet, simply a truck with more power. But for my situation and plans to not tow over 4k pounds, I am extremely happy with the Gladiator on 37s w/5.13s.

 

[Deleted member 28696]

Got 5.13s in April, drove 500 miles and changed the gear oil, then drove 4100 miles from NJ to CO and back the past 10 days. I towed a 2,350# 5x8 uhaul enclosed trailer without brakes and the JT weighed 6,920 w/3 passengers and full tank of gas. The trailer towed like it wasn't behind me except I could feel it when there was a strong crosswind or sometimes passing a semi. The braking distance was a little impacted but not by much. Refresher - I have JTR with 37s and 3in lift with accessories including RTT on 1/2 bed rack, 1/2 roof rack over cab, 270deg awning, winch, plus some other accessories.

Avg 10.8 mpg heading to CO and 11.7 coming back so that's a total trip average of 11.2 (hand calculated). Just over $1500 was my fuel bill ? and that was about $450 more than my fuel bill for the same trip in January (I didn't tow a trailer then and averaged 11.9mpg). Just like in January, I was driving an average of about 5 mph over the posted speed limit throughout the trip. I believe 2-3 mpg could be gained if I didn't exceed 65mph vs the 75-80mph I was pushing the brick.

Bottom line is I'm really happy with the 5.13s on both highway and off-road. Shop recommended the 5.13s over the 4.88s and they were right. I was also happy with being able to do 65mph going up the steep, long and high altitude CO passes without the engine close to redline but I can see why others that are consistently towing significantly more weight up the passes might want 5.38s, or better yet, simply a truck with more power. But for my situation and plans to not tow over 4k pounds, I am extremely happy with the Gladiator on 37s w/5.13s.

The shop that I went to doesn’t recommend 5.38’s since the pinion gets too small was how they explained it. 5.13’s are as deep as they will go without an complete swap to Dana 60s, 80s. I agree that 5.13s are the way to go with 37’s. I get around 13.3 mpg according to the computer. Was getting just over 3MPG more on 37’s 3” lift until I added the RSI smartcap. Then I needed to swap springs in the rear to accommodate the additional weight.

 

[Muddzy]

The shop that I went to doesn’t recommend 5.38’s since the pinion gets too small was how they explained it. 5.13’s are as deep as they will go without an complete swap to Dana 60s, 80s. I agree that 5.13s are the way to go with 37’s. I get around 13.3 mpg according to the computer. Was getting just over 3MPG more on 37’s 3” lift until I added the RSI smartcap. Then I needed to swap springs in the rear to accommodate the additional weight.

It's interesting. I called several shops and gear swap pricing varied from $1675 to $3400. Most shops were in the $2200 - $2400 range with the high and low prices represented by 1 shop each. The shops also varied in their gear recommendations...most recommended 4.88 but would do 5.13 if I wanted. Only 1 shop, the shop that did the most regearing jobs by far, recommended for me to do 5.13s and they would've done 5.38s if I said I planned to go to bigger tires. They had a bunch of modified jeeps they were working on and they knew their stuff when it came to off-road and gears. What it really comes down to is what type of driver a person is. If they are light on the pedal and know when and how to properly use the pedal to off-road then 5.38s will work. If a person is punchy with the pedal or is doing a lot of mud crawling where the tires are spinning and then can suddenly catch, then the smaller pinions might not hold up. But I have no problem with a shop not knowing the driver and therefore not wanting to install 5.38s in stock Danas. In the end, a "reckless" driver can break 4.10s, too.

 

[Ole Cowboy]

You gots to be cautious when playing tires and gears. What gain on the bottom you lose on top! One of my Jeeps had 5:38s and I could not drive that rig much faster than about 55 mph. But I was wheeling local and that was fine.

My daily driver was 37s and 4:88s and I put almost 100k miles on that rig.

FYI: 37s and 4:88 and a 3 in lift will spank any trail out there...in 10 years of full-time wheeling across the US and Mexico I was NEVER defeated by a trail and only played on the most difficult of trails like Pritchett Canyon in Moab..done it forward, back and by myself and never pulled a winch rope or a strap. Ran it many many times in 13 trips to Moab.

 

[Muddzy]

You gots to be cautious when playing tires and gears. What gain on the bottom you lose on top! One of my Jeeps had 5:38s and I could not drive that rig much faster than about 55 mph. But I was wheeling local and that was fine.

My daily driver was 37s and 4:88s and I put almost 100k miles on that rig.

FYI: 37s and 4:88 and a 3 in lift will spank any trail out there...in 10 years of full-time wheeling across the US and Mexico I was NEVER defeated by a trail and only played on the most difficult of trails like Pritchett Canyon in Moab..done it forward, back and by myself and never pulled a winch rope or a strap. Ran it many many times in 13 trips to Moab.

I agree in concept. The 8 speed auto transmission opens up a lot more top end, even for 5.38s vs the older 6 speed. And you sound like a true off-roader who knows what they're doing. If your rigs are 2 doors or even 4 doors then they are substantially lighter than the Gladiator. That said, i believe 4.88s and 37s are fine for dedicated off-roading in a Gladiator. In my situation, I overland and tow off-road so lower gearing helps with the weight. And you won't find my Gladiator on Pritchett Canyon!

 

[hjdca]

I have a manual Rubicon with 37s and 5:13s. After using them for 1.5 years, Personally, I am really glad I went with 5:13s. Some additional reasons for 5:13s and 37s besides fwy speed, rpm, mileage:

1. Best Acceleration you can get from 0 to 60. It's nice to go suprisingly fast on an on ramp to a fwy. Even in 2nd and 3rd gear (manual) with 37s, you can feel the truck take off after 5K rpm.
2. Lower granny gear for rock crawling. Even with the 4 to 1 transfer case of the Rubicon, I really appreciate the lower granny gear in the rocks.

 

[Ole Cowboy]

I agree in concept. The 8 speed auto transmission opens up a lot more top end, even for 5.38s vs the older 6 speed. And you sound like a true off-roader who knows what they're doing. If your rigs are 2 doors or even 4 doors then they are substantially lighter than the Gladiator. That said, i believe 4.88s and 37s are fine for dedicated off-roading in a Gladiator. In my situation, I overland and tow off-road so lower gearing helps with the weight. And you won't find my Gladiator on Pritchett Canyon!

The 4:88/37 combo is great and I believe even greater with the 8-sp auto, that should make a super rig. I have only owned 1 4 door Jeep and after about 3 mo I traded it in. The Glady is actually my wife, she LOVES it. My current rig is a '17 Rubicon Recon edition. It is an auto but I put up with than. I remember the days when an Auto trans was Special order and the dealer would make you put down a $2500 NON REFUNDABLE deposit. You could NOT sell an automatic...

 

[FL Handle Guy]

I'm running 4.88 with 37 BFG ATs LR-C. They are light and more like 36"s. I'm getting 17 with a camper shell, deked and crossbars installed.

So far I am quite happy with it. I lost some MPG when I went from 35 Patagonia to the 37 BFG and about 1-1.5 with the camper shell. So, now I am back to where I was on the 35s before turning it into even more of a brick. Also, power feels the same as it did with 35s only a small difference in braking power.

I'm a flatlander but will be trying out the 4.88s and light/small 37s in CO and Utah soon and will update. I'm sure I will be happy with it though.

I also chose the 4.88s because if I were to get a pull behind camper I would drop down to 35"s and I felt that 5.13 would be too deep.

 

[Ole Cowboy]

I agree in concept. The 8 speed auto transmission opens up a lot more top end, even for 5.38s vs the older 6 speed. And you sound like a true off-roader who knows what they're doing. If your rigs are 2 doors or even 4 doors then they are substantially lighter than the Gladiator. That said, i believe 4.88s and 37s are fine for dedicated off-roading in a Gladiator. In my situation, I overland and tow off-road so lower gearing helps with the weight. And you won't find my Gladiator on Pritchett Canyon!

If you really go hardcore, the 4:88 have got the thick pinion, beyond that, they start getting smaller unless you go with a bigger axle group. In the rocks especially in Moab and while they call it "Slick Rock" there is NOTHING slick about it, the grip is incredible. A lot of axles get snapped and a whole bunch of u joints gets broken. TIP if play hard rock, I run 1310 u joint at the front/rear axle pinions. The reason for that is that the 1310 acts as a fuse. IOW its the FIRST to break and the easiest to fix on the trail. Don't even need to move the jeep, just slide under and replace.

Back in the days when I was going to Moab more often than changing underwear I got to know a LOT of people up there. One week I was there I a call just after I had down some early morning runs and came back to my motel room and I got a call that a guy in Pritchett Canyon was in a wedge and they could not get him out. It was a well built Jeep and they did not want to call for helicopter service at $2k+++. So head out and go in and find him, what a bind he was in. The Jeep and rolled over on its side and then slide in a wedge. I was able to get him out and get him back to the hardtop. Not easy as dragging him out broke both the U shackle on his spring to axle connection. Now get this: We are standing around trying to figure out what to do. I had drug him about 50+ yards and destroyed the body. I said I happen to have 2 Mil-Spec nylon Zip ties and are used in M 1 Tanks. Been in the back of my Jeep for years, they are STRONG. So I got under his front axle and criss-crossed them around the axle and the spring. I told him to drive in 2 wd and I will get you out of here and back to Moab and I did, not easy but I got him out.

IMO Pritchett Canyon is more skill than Jeep, but you got to have a serious

Jeep build to even tackle it, then its all driver.

The guy got it home on a flatbed and called me later to say he had to replace the entire body, all sheet metal.

 

[wanderer]

I have been running BFGoodrich all terrains in a 37 with a metal cloak 3-5 inch lift stock 410 gears on the rubicon automatic transmission. My mileage sucks usually around 13-14 running at 75 mph . in so cal you pretty much have to drive like that here.
Been thinking of regearing to 488 what can I really expect in mpg? I hear folks claiming 19 but find that hard to believe especially when my little Hyundai Santa Fe. Barely eaks out 24 mpg

Part 2 what is the quietest 37 inch inch tire made. And do they stay quiet when you have rolled up 40 k on them?

 

[steve68]

I recently installed 37" Ridge Grapplers and Forgelines, each one is 105lbs, I removed the stock ones at 85.5 lbs, Of course wind and terrain could play havoc on this traveling last week, Factory wheels, the convertor would unlock and the RPMs would drop to like 2100 rpm, with the 37's, It would only unlock every now and then, mainly the RPM's stayed at 2500RPM's

I did have the trans reprogramed when I bought it, it wasn't wanting to unlock then it was fixed,

So now is it gear ratio or trans problem, Greenway can never duplicate the problem on there little back road drive around!

 

[Jeeperjamie]

I have been running BFGoodrich all terrains in a 37 with a metal cloak 3-5 inch lift stock 410 gears on the rubicon automatic transmission. My mileage sucks usually around 13-14 running at 75 mph . in so cal you pretty much have to drive like that here.
Been thinking of regearing to 488 what can I really expect in mpg? I hear folks claiming 19 but find that hard to believe especially when my little Hyundai Santa Fe. Barely eaks out 24 mpg

Part 2 what is the quietest 37 inch inch tire made. And do they stay quiet when you have rolled up 40 k on them?

I get over 17 miles per gallon on 410 gears and 37s so it's realistic to think you could get close to 19. We have seen the mid 18's on longer trips.

Your running the quiet 37 pretty much and they all get louder the closer the 40,000 you get

 

[sholland96]

Just thought I'd add our data... We have an AEV JT370, which came with 4.56 gears and 37" KM3's. It get ~17mpg on the highway and has great acceleration.

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