Gears vs tires question.

[33Jayman]

My Gladiator has 4.10 gears. It is a Mojave. I have read that you can easily run 35" tires on it. I have a JK Wrangler 2DR. It has 3.73 gears and I run KO2, 315x 70R 17s on Raceline wheels. I have the JScan app and I can adjust my tire size (among other things) to correct the shift points. My JK does great with this set up.

Here is my question. If my Gladiator with the 4.10 gears is capable of turning 35" tires. Is it going to be ok with 35 1/2" tires? I ask because KO3, 37s actually measure 35.5 inches. They are not a 37 inch in diameter tire. So when I ask pros and very experienced Jeeper if I can run 35s they all say sure can, no problem, shouldn't every have a problem etc. So I guess I should ask, "Ok how about undersized 37s, or a big for class 35?"

I would use my JScan app to adjust for tire size just as I did on my JK. Well infact I did already change the setting on my Gladiator as the Falken Wildpeaks are only like 32 1/4".

It shoudl be noted that we bought the Gladiator new and we picked it up 4 weeks ago tomorrow.

Jayman

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[MaximusTX]

My Gladiator has 4.10 gears. It is a Mojave. I have read that you can easily run 35" tires on it. I have a JK Wrangler 2DR. It has 3.73 gears and I run KO2, 315x 70R 17s on Raceline wheels. I have the JScan app and I can adjust my tire size (among other things) to correct the shift points. My JK does great with this set up.

Here is my question. If my Gladiator with the 4.10 gears is capable of turning 35" tires. Is it going to be ok with 35 1/2" tires? I ask because KO3, 37s actually measure 35.5 inches. They are not a 37 inch in diameter tire. So when I ask pros and very experienced Jeeper if I can run 35s they all say sure can, no problem, shouldn't every have a problem etc. So I guess I should ask, "Ok how about undersized 37s, or a big for class 35?"

I would use my JScan app to adjust for tire size just as I did on my JK. Well infact I did already change the setting on my Gladiator as the Falken Wildpeaks are only like 32 1/4".

It shoudl be noted that we bought the Gladiator new and we picked it up 4 weeks ago tomorrow.

Jayman

You are going to get a ton of different responses when it comes to tires and gear ratios. My first JT was a Gas with 3.73 gears and I ran 35s on it. I rarely hit 8th gear. Can your 4.10s run 35.5 inch tires yes. Is it the optimal ratio for the size maybe, maybe not. Now I run 42s on 4.88s and it is perfect for the Diesel. Here is the basic gear ration chart from my local shop Exodus 4x4.

(New Tire Diameter ÷ Old Tire Diameter) × Original Gear Ratio = New Target Gear Ratio

(37 ÷ 35) x 4.10 = 4.33 so in this case 4.56

 

[LoadnGo]

The really tricky part- tire diameter listed by manufacturers are NEVER EVER accurate, regardless of what rim width you have or whether they are on the vehicle or laying on the floor in your shop. The diameters listed by manufactures are ALWAYS larger than they actually are, on or off the vehicle. I've owned 10 Jeeps including a '52 CJ2A, several CJs, a Grand Wagoneer, Cherokees, a TJ a JK and now my '24 JT. I have upsized tires 5 times and re-geared three. My point- physically measure the tires you intend to use mounted on wheels and on someone's rig. Otherwise, you WILL NOT have accurate data to make gear swap decisions. Better yet- find a Jeeper that has the exact setup you THINK you want and take it for a spin. Then you'll know for sure how to proceed.

 

[JohnAmigo]

You are going to get a ton of different responses when it comes to tires and gear ratios. My first JT was a Gas with 3.73 gears and I ran 35s on it. I rarely hit 8th gear. Can your 4.10s run 35.5 inch tires yes. Is it the optimal ratio for the size maybe, maybe not. Now I run 42s on 4.88s and it is perfect for the Diesel. Here is the basic gear ration chart from my local shop Exodus 4x4.

(New Tire Diameter ÷ Old Tire Diameter) × Original Gear Ratio = New Target Gear Ratio

(37 ÷ 35) x 4.10 = 4.33 so in this case 4.56

So in reading this chart... I can avoid upgrading my gears, if I upgrade the engine... "SOLD"! hahahah


I need to work the girl math on this...
Axle gears upgrade -> ~ $5K

All I get is happier drive train

Engine Upgrade -> ~ $30K

I get a happier driver and save $5K

 

[MaximusTX]

So in reading this chart... I can avoid upgrading my gears, if I upgrade the engine... "SOLD"! hahahah


I need to work the girl math on this...
Axle gears upgrade -> ~ $5K

All I get is happier drive train

Engine Upgrade -> ~ $30K

I get a happier driver and save $5K

Makes Sense to me it's basically free and you make money while it is in the shop getting the swap done.


The Girl Math Breakdown

• You are saving $25,000: By refusing to spend $5,000 on "just some gears" that nobody can see, you are avoiding a bad micro-transaction. That is basically a $25,000 discount toward the engine.
• It pays for itself in time: A gear change takes days at a shop. An engine swap takes weeks or months. That is months of you not driving, which means zero money spent on gas, parking, or fast-food drives. The car is practically making you money by sitting in the garage.
• Cost per horsepower: Spending $5,000 for 0 extra horsepower is infinite dollars per horsepower. Spending $30,000 for 200+ extra horsepower is a massive bargain.
• The "Same Gearing" loophole: Since you are keeping the stock gears, you spent $0 on gearing. You literally saved 100% of your gearing budget.
• The Happier Dividend: Happiness is priceless. If you divide $30,000 by a lifetime of hearing a massive engine roar, the cost per day rounds down to zero. It is basically free.

 

[JohnAmigo]

Makes Sense to me it's basically free and you make money while it is in the shop getting the swap done.


The Girl Math Breakdown

• You are saving $25,000: By refusing to spend $5,000 on "just some gears" that nobody can see, you are avoiding a bad micro-transaction. That is basically a $25,000 discount toward the engine.
• It pays for itself in time: A gear change takes days at a shop. An engine swap takes weeks or months. That is months of you not driving, which means zero money spent on gas, parking, or fast-food drives. The car is practically making you money by sitting in the garage.
• Cost per horsepower: Spending $5,000 for 0 extra horsepower is infinite dollars per horsepower. Spending $30,000 for 200+ extra horsepower is a massive bargain.
• The "Same Gearing" loophole: Since you are keeping the stock gears, you spent $0 on gearing. You literally saved 100% of your gearing budget.
• The Happier Dividend: Happiness is priceless. If you divide $30,000 by a lifetime of hearing a massive engine roar, the cost per day rounds down to zero. It is basically free.

This is great!

 

[djthumper]

The chart shows what I have been saying they should have had in all diesel gladiators. We should have 4.10s from the factory. I am on 35s and still get around 20 MPG with the diesel but there are times with our rolling roads around the valley it always seem to search before it decides a gear to stay in. I can be at 23 MPG going into work and coming back from work drop down to 20.5, I drive 70 miles round trip.

 

[LoadnGo]

2024 JT 3.6L 850RE- tires measure 32.75" installed

my very recent swap was a total of 1&1/2 days- performed at a top tier, long standing shop for $3,000, plus tax. Revolution gears (4.56). The only vaguely perceivable down-side is that the shop was a whole 41 miles from home. Actually made me have to stop at a BBQ place 1/2 way back for a delicious meal and a 3 hour cool down. Break-ins are tedious, so you have to commit yourself for at least the first 200 miles to go easy. If your shop is far off, consider towing it home on a trailer to begin the proper break-in. And, my Gear Swap Guy said he would do the 1st fluid change (gonna be at 300 mi. for me) included in the original price. Top Tier Shop- $3000/1.5 days/41 miles away. 1st fluids and inspection included.

BTW- immediate gratification. Fuel economy jumped several mpg immediately, and that's around town at under 50 mph! Shifts are firm and on time, no more lagging behind. downshifts are just right. can't wait to hit the highways at my usual 65-71 mph speeds and watch the mpg increase even more.

Don't forget!!! If running heavy- or Rock Crawlin', towing often and/or rigging out an Expeditionary style rig- go up one more gear for best results. Just my 2c.

 

[33Jayman]

The really tricky part- tire diameter listed by manufacturers are NEVER EVER accurate.

This^. This is the most frustrating puzzle to figure out. There is a post on another forum that is a bit older but it is all about actual tire size verses manufacturer stated tire size. People have chimed in and given their real world tire diameter measurements. Almost all are well under the size that the manufacturers say they are. That is where I learned that the 37" KO3s actually measure 35.5'.

Jayman

 

[Capngeo]

I've got the stock 3.73 on 35's with the 3.0. Fuel mileage around 20 in mixed driving. More if I keep her below 1500rpm, I've seen 30 mpg on road trips (55-60mph in FLAT Florida). PLENTY acceleration, great off road performance.

Gear threads are like oil threads: lots of opinions about what is best for THE WRITER. In the real world you need to look at where and how YOU drive to determine what ratio is best for YOU. Here in FL, where it is mostly flat and most of the off roading is either mud or sand a 3.73 is perfect for ME. Now the guy who lives in the mountains or rock crawls the high desert gears into the 5's are not unreasonable.

Don't get swayed by opinions or marketing, do your research for your area and driving habits; back it up with mathematical evaluations and real-world feedback from LOCAL owners.

Good Luck!

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