Gear set ratios for the Eco diesel 37 inch tire upgrade verse the Gas engines (difference?)

[Sniper]

I have a question about AEV gear ratios. I ordered a Diesel Rubicon Gladiator from FCA through a Jeep & AEV Dealer (American Expedition Vehicles) near me with the JT 370 package. My build was framed on March 8th, painted on the 9th, it went through chassis and trim on there after and shipped to the local Detroit dealer for inspection on the 12th, then will go to AEV for the JT 370 upgrade conversion.

I want to review some numbers with you and see if anyone can explain them to me. I listed all my references in my screen shot which I reference all three gear ratio sets. The stock 3.0 ecodiesel gears are 3.73 as oppose to the 3.6 gas engine is 4.10 gears. A tire increase from stock to the 37 for the diesel would be a 4.22 gear ratio so closest would be a 4.10 gear set, yet I'm getting a 4.56 gear set from AEV which is closer to what the 4.10 gear set on the gas would need if it gets increased to a 37 inch AEV which would be the 4.56 gear set.

It appears to me Jeep put a 3.73 gear set in the diesel was due to the higher torque at the low end therefore FCA specifically used two different gear sets for the two different engines. I also found a youtube video showing the dyno power band of the diesel with the 3.73 and it's impressive and did not need a 4.1 like the gas.
My end use will be as a secondary driver, expedition / outlander trips and very little off road / rock crawling... My question is should I be concerned with the 4.56, that it will be geared a little bit too low on the low and high end and lose something on the high end or throw my automatic transmission clutch speed changes off? If AEV followed Jeeps math for their gears then they would put the 4.10 on the 3.73 diesel and the 4.56 on the Gas, but the 4.56 is applied to both. Do you think AEV considered the different power bands between the diesel and the gas engine?

What I cannot get answered is the logic for the 4.56 applied to both vehicles. I get everyone says "it will be fine" but the logic and in this case the math does not agree.

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[MattK]

I don't have an answer for you but AEV is easy to talk to in my experience in dealing with them over the phone on other products. You're paying for it so make sure you get what you want and you think makes sense.

 

[Sniper]

I don't have an answer for you but AEV is easy to talk to in my experience in dealing with them over the phone on other products. You're paying for it so make sure you get what you want and you think makes sense.

I just sent them an email, thanks.

 

[CrazyCooter]

You will be good either way. I would do 4.10s for a light highway cruiser that occasionally tows light or 4.56 for a heavy build that drives mainly mountains , tows heavier, has a lot of wind drag from lights/rack, or otherwise wants to end up on the performance side

I'm pretty happy with 37s and 3.73s but all I've towed is 1300lb and some gear in the truck. I'm going to choose whether or not to install 4.10s until after I tow my 3000lb RV in the mountains.

Also if you plan to add an engine tuner, you could probably do the 4.10s due to the extra power available.

In the end its only about 150-175 rpm difference at highway speed.

 

[AustinKalb]

I just sent them an email, thanks.

I have the EXACT same question. What did you find out? Details pls. Thx.

 

[Sandevino]

Short of a one-off specialty gear set, 4.22’s don’t exist. Going up to the next mathematically close common gear set provides reliability and allows you to service or repair the gears relatively easily. The diesel will be happy with either 4.10’s or 4.56’s and you’ll get great low end power right in the diesel power band.

 

[Escape.idiocracy]

Geesh…. 37’s I would look to go 4.88’s. But we have always been in favor of a crawl ratio vs a couple hundred higher spin on the highway.

What is the concern/driver of the question? Do you feel like 4.10’s would have been a “better” option?

Another perspective of this- maybe FCA didn’t really mail the ratio with 3.73’s? I don’t want to make another Derating thread andargue The effects of transmissions vs torque multiplication….. but I would rather be geared a at 4.56’s than 4.10’s with 37’s…. And really if I had my choice- 4.88’s for 37/38” tires 5.13/538’s for 40’s…. Better to have and not need them need and not have.

 

[Trout Safari]

I can only answer your questions from experience in the drivers seat with my foot on the pedal, not from a paper standpoint. I have a 2022 Diesel on 37's. I also tow a Turtleback off road trailer at times. After installing the 37's I did notice a lag at the start and when running at low and higher speeds. I really noticed the transmission attempting to shift between 7-8 gears quickly at times back and forth when towing the trailer at higher speeds and not the pedal control I liked off road.
I switched to 4;56 gears and I can say it feels like a whole different truck. Great power off the line with no lag. Smooth shift changes and the ability to stay in a gear at higher speeds on the highway towing a trailer. For me I feel the difference is huge. I have re-geared many Jeeps over the years and I can honestly say this was the biggest change in performance I have seen yet.

 

[DavoSmith]

I can only answer your questions from experience in the drivers seat with my foot on the pedal, not from a paper standpoint. I have a 2022 Diesel on 37's. I also tow a Turtleback off road trailer at times. After installing the 37's I did notice a lag at the start and when running at low and higher speeds. I really noticed the transmission attempting to shift between 7-8 gears quickly at times back and forth when towing the trailer at higher speeds and not the pedal control I liked off road.
I switched to 4;56 gears and I can say it feels like a whole different truck. Great power off the line with no lag. Smooth shift changes and the ability to stay in a gear at higher speeds on the highway towing a trailer. For me I feel the difference is huge. I have re-geared many Jeeps over the years and I can honestly say this was the biggest change in performance I have seen yet.

Thank you for your real world insight. How do you think a heavy Jeep Gladiator with Eco Diesel would do with 4.88 gears? I'm planning out a daily driver, rock crawling, overland land (I really hate to use that term) family camping rig. Diesel JT with Dynatrac 72.5" wide 60/80 Elite Axles, 40-42" tires, decked drawer system (205 lbs), GoFastCamper Platform Camper (270lbs), 15 gal extra diesel, 10 gal water, frig/freezer, camping/hunting gear..... My two choices from Dynatrac are 4.88 or 5.13. I'm thinking the 4.88 would be better for highway, high altitude mountain pass driving.

What do you think?

 

[Escape.idiocracy]

Thank you for your real world insight. How do you think a heavy Jeep Gladiator with Eco Diesel would do with 4.88 gears? I'm planning out a daily driver, rock crawling, overland land (I really hate to use that term) family camping rig. Diesel JT with Dynatrac 72.5" wide 60/80 Elite Axles, 40-42" tires, decked drawer system (205 lbs), GoFastCamper Platform Camper (270lbs), 15 gal extra diesel, 10 gal water, frig/freezer, camping/hunting gear..... My two choices from Dynatrac are 4.88 or 5.13. I'm thinking the 4.88 would be better for highway, high altitude mountain pass driving.

What do you think?

Dirt lifestyle on YouTube went with 5.13’s and has gone on a decently long road trip- extensive off road…. He went 5.13’s and small side BFG 39” tires…. He has complained none…

personally- 5.13’s give you the more when you need it (mechanical advantage). The couple hundred rpm difference isn’t going to be that big on the highway… we are splitting hairs from a motor perspective. From a rolling mass perspective 40-42” tires are substantial… you have the axle girth that the pinion head isn’t a concern- go 5.13’s is my vote.

 

[Wango's Tango]

I have a 2022 JTRD, AEV package same as yours. In the beginning i sat down with a friend who is a general manager of a custom off road shop. We talked about the gears, i had a similar thought as yours. Were they the right ones, he thought AEV was right in choice they made. He also pointed out the warranty issues if they were wrong.
That being said, when i regeared my full size adventure truck and switched to 37' on it, he put in 4.88s.

 

[Trout Safari]

Thank you for your real world insight. How do you think a heavy Jeep Gladiator with Eco Diesel would do with 4.88 gears? I'm planning out a daily driver, rock crawling, overland land (I really hate to use that term) family camping rig. Diesel JT with Dynatrac 72.5" wide 60/80 Elite Axles, 40-42" tires, decked drawer system (205 lbs), GoFastCamper Platform Camper (270lbs), 15 gal extra diesel, 10 gal water, frig/freezer, camping/hunting gear..... My two choices from Dynatrac are 4.88 or 5.13. I'm thinking the 4.88 would be better for highway, high altitude mountain pass driving.

What do you think?

I dont think what your carrying for weight is an issue. I carry that and a 4500 lb trailer. I can say with 37's I am glad I didnt go with a 4.88. The 4;56 is just perfect for my set up. In your case I really can't tell you. A 42" tire on a Jeep is huge. I am sure it will look cool, but I honestly do not know what it will take to push those well. I had 40's on a Ford f-250, but have never had bigger than 37's on a Jeep. Talk to someone that actually has 40+ tires an a Diesel Jeep and ask them those questions. I always like first hand knowledge and we all know people on the internet that have never had the combo your thinking of have the most advice.

 

[CrazyCooter]

I'm on 38's w/ 4.10's and I like it! I tow a 4K RV with a moto in the bed at times and wouldn't change a thing........Can tow on the flats in 7th, 6th in the rolling hills, and still have 8th for economy while unloaded.

23-25mpg on 38's? Just isn't right for a Jeep..........

 

[Drooler]

I have a 2022 JTRD, AEV package same as yours. In the beginning i sat down with a friend who is a general manager of a custom off road shop. We talked about the gears, i had a similar thought as yours. Were they the right ones, he thought AEV was right in choice they made. He also pointed out the warranty issues if they were wrong.
That being said, when i regeared my full size adventure truck and switched to 37' on it, he put in 4.88s.

Thanks to all that contributed to this thread. Am keen to hear updates from folks who did the re-gear.

FYI. Recently bought a new 2023 Gladiator FarOut and in the process of getting it modded.

Will have a winch, 3.5” MetalCloak lift kit, skid plates, front drive shaft, truss & gussets, ARES cap, etc. Goal is to do the Rubicon at some point.

Was doing one trip a year to Moab / Ouray in my old 2015 JKUR with 3.5” AEV lift, 35” and skid plates. And fingers crossed will continue to do so with the new Gladiator.

First time Gladiator owner and also a first time Diesel engine owner. Am undecided between 37” and 40” tires. I suspect I will start with the 37” & in a few years switch out to 40”s.

At least that is what my Mod shop guy thinks will happens. He said he has seen too many start out with 37”s and
upgrade to 40”s.

Given I have to tow a 4,000 lbs trailer every other month, he suggested 5.13 gearing.

Based on what I read in this thread, 4.88 is more than enough even if I go up to 40” tires which is the max that Jeep Jamboree will allow on their official events.

Anybody has done 4.88 gears and regretted with 40s (wishing you had done 5.13)?

On the flip side has anybody with 40” tires done 5.13 gears and regretted not going with 4.88?

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