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Who is running 37"-40" tires on the diesel

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so why do they keep a consistent 3.73 gear ratio- even though they offer different size tires between the different models…?
For the same reason the trans gears are identical? Conformity? Some emissions standard?

Let's face it; there's a 2" difference between the shortest and tallest of the 3 tires offered from the factory and the MPG stats on the 31 and 32" tires are identical but the 33s are starting to slip which may or may not have been recouped with an increase in gear ratio.
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CrazyCooter

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so why do they keep a consistent 3.73 gear ratio- even though they offer different size tires between the different models…? 🧐🧐🧐

We are going 4.88’s on 38’s/40’s
Also be getting the gde Canadian/Mexican tune.

engine oil temp is the biggest driver and then crawl ratio.
My guess is they are limited by the availability of a taller R&P not being available for the front M210?

We had the same issue with the 2005+ 3rd gen Rams with the G56 trans. OD ratio wasn't really tall enough, but 3.73 was the tallest ratio available for the front axle at the time. Then 2007 they changed the OD ratio in the trans and also offered a 3.42 on top of that in the later years too. I found 37's and 4.10's to be the sweet spot for my 5.9 Cummins even running up 30K+ GCVW.
 
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It maybe the carrier in the diffs that you don't see gears like a 3.43 installed. With a 3.73 carrier, you can go deeper like 5.13'. With a carrier with a 3.43. You might be limited to how deep you can go. Maybe 3.90. Just tossing this out. I seen this happen before.
 
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I'm about to make a 3,700 mile trip on 40's and a full "overland" setup with about 800lbs of extra gear. I'll report back what I get. On 37's I could easily do 23mph with the same "overland" setup. I expect to be in the high teens, maybe
 

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I'm about to make a 3,700 mile trip on 40's and a full "overland" setup with about 800lbs of extra gear. I'll report back what I get. On 37's I could easily do 23mph with the same "overland" setup. I expect to be in the high teens, maybe
Look forward to you reporting back 👍🏼
 

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For the same reason the trans gears are identical? Conformity? Some emissions standard?

Let's face it; there's a 2" difference between the shortest and tallest of the 3 tires offered from the factory and the MPG stats on the 31 and 32" tires are identical but the 33s are starting to slip which may or may not have been recouped with an increase in gear ratio.
This and:
It has nothing to do with you or me. The factory engineered the engine/ drivetrain/ tire size to work optimally together within certain parameters.

Doesn’t make sense to me…. If conformity and production consistency were really the driver… then why are 4.56 gears offered on their gas package with 35’s???

why does the gas rubicon come with 4:10’s and the other packages come with 3.73’s etc…..

There is likely a reason….. but these above statements do not make sense- to me at least.

what ratio is offered with the 392 package?? I know that the 4:1 transfer case isn’t an option- probably a similar justification??
 

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My guess is they are limited by the availability of a taller R&P not being available for the front M210?

We had the same issue with the 2005+ 3rd gen Rams with the G56 trans. OD ratio wasn't really tall enough, but 3.73 was the tallest ratio available for the front axle at the time. Then 2007 they changed the OD ratio in the trans and also offered a 3.42 on top of that in the later years too. I found 37's and 4.10's to be the sweet spot for my 5.9 Cummins even running up 30K+ GCVW.
Isn’t the M210 the same axle used with the recon package though??
 

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Curious. Any concerns with warranty when you guys regear?
Personally I’m not worried about it- if the dealer is going to go down the road of whatever item (assuming transmission or motor) that the claim is being put in for; they are likely going to argue larger tires did the damage as much as the gearing…. 🤷🏽‍♂️ Sometimes it’s worth finding the dealer that isn’t going to be a pain in the ass and is willing to work with you and having modifications… if I’m going in for a dealer visit- that’s who I am throwing money at.
 

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We are going 4.88’s on 38’s/40’s
Also be getting the gde Canadian/Mexican tune.
She's gonna be a beast. Hope a delete kit comes with it!

Doesn’t make sense to me…. If conformity and production consistency were really the driver… then why are 4.56 gears offered on their gas package with 35’s???

why does the gas rubicon come with 4:10’s and the other packages come with 3.73’s etc…..

There is likely a reason….. but these above statements do not make sense- to me at least.

what ratio is offered with the 392 package?? I know that the 4:1 transfer case isn’t an option- probably a similar justification??
I think you're in Wrangler territory now.
As far as Gladiators go (and only 22my is coming up on the Jeep website) gas Rubicons and Max tow sports are offered in 4.10, everything else 3.73.
Rubicon wranglers have 4 different gear ratio options but I think most of those are connected to different engines/ packages.
There's no real stand alone gear ratio options that I can tell.
 

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The big driver is torque and shock loading. I'm fairly certain the bean counters sat down with legal and then invited the 392 team into the meeting whereupon everyone agreed that most 392s are not going to be used right or well and the 4:1 low range represented a "liability" when people opt to do a 4 wheel burnout only to detonate the transfer case.

This same torque and shock load argument comes into play with the diesel, it carries the 3.73 ratio across the board as well as the same transmission because its rated for the power output. It may not have ideal ratios but it can take the load.

The factory 35s come with 4.56 so the wrangler can scoot on par with the 4.10s on a stock base rubicon. Your average driver/buyer might not like the otherwise lack of throttle response and motivation/enthusiasm.

Tall tires and high ratios would give us amazing economy numbers and abismal acceleration with the suprise bonus of way too much shifting based on road conditions and elevation changes.
 

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The big driver is torque and shock loading. I'm fairly certain the bean counters sat down with legal and then invited the 392 team into the meeting whereupon everyone agreed that most 392s are not going to be used right or well and the 4:1 low range represented a "liability" when people opt to do a 4 wheel burnout only to detonate the transfer case.

This same torque and shock load argument comes into play with the diesel, it carries the 3.73 ratio across the board as well as the same transmission because its rated for the power output. It may not have ideal ratios but it can take the load.

The factory 35s come with 4.56 so the wrangler can scoot on par with the 4.10s on a stock base rubicon. Your average driver/buyer might not like the otherwise lack of throttle response and motivation/enthusiasm.

Tall tires and high ratios would give us amazing economy numbers and abismal acceleration with the suprise bonus of way too much shifting based on road conditions and elevation changes.
I think we are on the same page.
I do find it an interesting compounding factor- the transmission tunes from the factory limit torque in first and second gear. If they are limiting tq through the transmission- why compound it with the differential limitation as well?

🤷🏽‍♂️ At the end of the day there are work arounds… gde tune, swap gear ratios… 🤷🏽
 

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They don't want you hanging a wheel in space, cranking it up and then slamming traction.

The flip side to all of this programing magic is they are also likely using the transmission as a retarder so the excess torque capacity is coming in handy there as well.

Think about doing a steep grade descent where gravity is pulling you down the grade briskly. Now think about the 4.10 gear set, you have a serious backdriven overspeed posibility in low 1st because for every 1 wheel rotation the pinion turns 4.1 times then the transfercase input spins 16.4 times...

If you can use the engine exhaust brake and the transmission retarded then you are able to "spill" both engine speed and road speed, dynamically.

But going the other way around, the axle gearing is likely mostly driven by CAFE concerns and to a lesser degree to keep the engine off the boil for cooling issues, the torque potential is probably third as unlike the 392, most people arent going to hoon their turbodiesel like a brodozer.
 

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I'm going to keep an eye on my rpms all the way home tonight, and see what speed is 2000 RPM in 7th and 8th gears, and then see if that's about my normal cruising speed. Science! Need more data. Will get back to this thread to confirm what we should be able to calculate based on this (among other things):

Cheers,
So this is what I wrote down last night:
2000 RPM: 6th gear: 56 mph
2000 RPM: 7th gear: 67 mph
2000 RPM: 8th gear: over 80 mph
1500 RPM: 8th gear: 62 mph

And I add that 4th row because driving around the vehicle wants to cruise around 1500 RPM. Of course with the pedal to the metal, it shifts between 3000 and 3500 RPM, but with no load it shifts up maybe at 1800 RPM to land maybe at 1300 RPM in the next higher gear. In fact, with no load (lift the pedal) it will shift into 8th at just over 60 mph, about 1450 RPM. And when slowing down, it doesn't shift down into 7th until 47 mph, about 1150 RPM.

So the claim that the engine wants to run at 2000 RPM is maybe right or not right for the original engine design, but it appears my jeep wants to run at 1500 RPM nominally (speed has been recalibrated, is accurate to better than 1 mph). For me, cruising speed is 1500 RPM, 62 mph in 8th gear, which is a very happy place for me. I definitely wouldn't call 1500 RPM lugging the engine. When I'm on the interstate (over 80 mph), if 2000 RPM is where it wants to live, then that is perfect for me.

My fuel mileage is based on a large part of my commute being at 53 mph, and I have no rack or tent and no winch; the only added weight is the Metalcloak control arms.

My point, to the original poster @Phil3333 , is that 37s and 3.73s perform quite adequately if you like these numbers I've given and have my commute and don't tow or haul a lot. Maximum acceleration is not my goal with this vehicle. Low range in Moab has also been fine with 3.73s IMHO.
 

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The diesel is torque limited in first and second gear. Plus under full power the 3.0L rev's up faster than it can reach full boost. You put larger tires on and it has more time at full power in 1st and 2nd.

It really does go good even with the huge tires. On the highway it does need to hit 7th on moderate hills but pulls in 8th usually. Works perfectly. The thing is 4.10's are too little gear and 4.56 is too much unless your on 40s so the factory 3.73 is worth keeping around.
I’m on 35’s with 4.56’s and assure you they aren’t too much. My mileage is virtually the same as when I had 3.73‘s and the same tires. Now it just runs a little cooler and EGT’s are noticeably lower pulling a load. It feels a bit snappier and more responsive as far as my butt dyno is concerned as well.
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