overboosted

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Sydwaiz

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I noticed that too and mentioned it in the other build tool thread. Hopefully it's a glitch or an option. My build sheet for my '21 does say 3.73 though. We will see when it arrives.
 

PillowFightr

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I cant wait to know this as well! I hope it comes with 4.10
 

DrRay81

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So I have a 2021 JLUR Diesel on order. my window sticker just posted today. anyhow I went to the jeep builder and noticed that on the 2020 builder a diesel rubicon will have the 3.73 gears. I was under the impression the 2021 diesels would also be 3.73. but on the builder it lists the diesel rubicon as 4.10's? is that an error on the website?
 

hazards280

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I've heard two sides to the story. Some believe that since the EPA ratings on the 2021s are down slightly that this proves the 4.10 gears. Others believe it's just an error on the Jeep website. Since the Rubi comes with 4.10s the system may not have captured the gear change when moving to the diesel.


We own a 2020 EcoDiesel and I have to say, I really don't see a reason for 4.10s with this drivetrain. It has more than enough get up and go, and I'd rather have the extra 1-2 MPG that I paid a little extra for. Keep in mind, I purchased the diesel more so for the driving experience than the MPG, but that's not to say I didn't place some value on the range. Also, I've read quite a few people are running 37s just fine with the 3.73 gears, so maybe the 4.10s would be valuable to folks going larger than this.
 

toolaide4fit

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The build tool on Jeep's site shows only 4.10's available with the diesel option now. A month ago it showed only 3.73's available. I ordered mine on 8/20. The order sheet doesn't state the axle ratio, just the Rubicon (26R), so I would guess I'm getting the 4.10s.
 

Jteakus

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I think those of us with 2020 EcoD Rubicons got shortchanged with 3.73's. The Sport Eco's have 3.73's with a 31.5" tire compared to our almost 33 inchers. Even the Ram trucks with the EcoD have an option for 3.92 gears with a 32" tall tire. The thing is designed to run a 35" tire after all. My .02
 

toolaide4fit

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The build tool on Jeep's site shows only 4.10's available with the diesel option now. A month ago it showed only 3.73's available. I ordered mine on 8/20. The order sheet doesn't state the axle ratio, just the Rubicon (26R), so I would guess I'm getting the 4.10s.
I have found the build tool just a little off occasionally. But I have never seen a build sheet to be wrong. The one above states 3.73 gears. I would find I very unusual to state this is what is being installed and then put something different in. Just don't see why they would change it unless there was some problem...but it is FCA after all.
 

Oilburner

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4.10's would be a nice option but I'll only believe it when I see it on someone's build sheet -
 

WXman

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That would be incredibly dumb. They should go 3.21s.

There is ZERO reason to do a deep gear ratio with a vehicle that only has a small power band and makes all its torque at 1,600 RPM, doubly so when it's mated to a great 8-speed trans.

This thing doesn't tow or haul any real weight, so 3.21s would give it better MPG with no sacrifices off-road. We're seeing that in the Ram application where the 3.21 guys are reporting much better mileage than the 3.92 guys.
 

Compression-Ignition

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That would be incredibly dumb. They should go 3.21s.

There is ZERO reason to do a deep gear ratio with a vehicle that only has a small power band and makes all its torque at 1,600 RPM, doubly so when it's mated to a great 8-speed trans.

This thing doesn't tow or haul any real weight, so 3.21s would give it better MPG with no sacrifices off-road. We're seeing that in the Ram application where the 3.21 guys are reporting much better mileage than the 3.92 guys.
I disagree with you completely. The Wrangler is a purpose built offroad vehicle. While some people might enjoy a 3.21 gear ratio, 3.73 is the sweet spot. 4.10s would be great for people wanting to run a larger tire, but a 3.21 is a little bit derp for Wranglers.
 

WXman

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I disagree with you completely. The Wrangler is a purpose built offroad vehicle. While some people might enjoy a 3.21 gear ratio, 3.73 is the sweet spot. 4.10s would be great for people wanting to run a larger tire, but a 3.21 is a little bit derp for Wranglers.
Sure, we can agree to disagree. The diesel has half the power band of the gas engine and makes nearly double the torque at nearly half the RPM. Completely different ballgame. You must throw every bit of conventional wisdom regarding axle ratios out the window. Nothing above 3.55 should even be on the order sheet. In fact, after driving this engine with 3.92 gears on oversized mud tires for the last six months I really regret not going 3.21. 1st gear is almost useless and the truck spends too much time shifting.

Up until recently every diesel engine offered in a truck/SUV in the last 40 years automatically came with numerically lower axle gears to properly match the power band. If you put 4.10s with a diesel, the result would be even more constant shifting. It's just asinine.

3.21 increases performance, MPG, and extends trans. life. And since the 8HP75 has a super deep 1st gear and a 2-speed t-case, it's the perfect ratio. They made it standard equipment on the Ram application and it should have been standard on the Jeep JL/JT also.
 

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