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Regear for Ecodiesel - What Ratio

Wrangler man

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The diesels are largely unknown still on optimal regear ratio because we’ve never had a factory option with this power. If it was a gas and you’re running 37s, it’s 5.13s all day long.

The worst thing with a diesel is to lug them or run to low of Rpms. My suggestion would be to go with a 4.88 max and 4.56 minimum. I prefer to run a little higher rpm and ensure it’s sitting in 8th on the highway over lugging it or forcing it to run in 7th at higher rpm than needed. The 8 speed has such a deep OD than the rpm difference isn’t that much but the extra power would really Wake the diesel up

congrats on the prize, that’s awesome.

brett
Since you have the regearing for free throw $600 into an iGage and pedal monster from Banks install it first. You'll be amazed! The torque and Power hiding inside your diesel is freaking incredible. I love mine
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Dasher320

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Thanks everyone for the commentary. I wouldn't mind getting feedback from folks that are have been running 37s and 4.56 or 4.88 whether they are happy and what style of driving they do (DD, overland or crawling).
I have had diesels before (SUV and big truck), but the Jeep is a different animal and I'm doing a different ride with this one as a full overland build on my JL. Thx!
I went with 4.56 on my JLURD on 37's. I do a lot of highway driving pulling a travel trailer and do a fair amount of rock crawling. I've put about 10k miles on the new gears and I like the 4.56/37 combo.

On the highway I get about 24-25 mpg not towing, about 14 mpg towing. I used to have a major issue with the engine temp rising while towing uphill--though I still watch it and it will rise on very steep passes, it has gotten better with the re-gear.

Just did a trip to Moab and it did great in the rocks. Did Hells Revenge, Fins & Things, Metal Masher, Sevenmile Rim, Elephant Hill, Top of the World, and some others and never felt even a little underpowered. In 4LO, I hit 8th gear at about 20 mph. It definitely shifts gears a lot more in 4LO after the re-gear.
 

JL2021guy

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I went with 4.56 on my JLURD on 37's. I do a lot of highway driving pulling a travel trailer and do a fair amount of rock crawling. I've put about 10k miles on the new gears and I like the 4.56/37 combo.

On the highway I get about 24-25 mpg not towing, about 14 mpg towing. I used to have a major issue with the engine temp rising while towing uphill--though I still watch it and it will rise on very steep passes, it has gotten better with the re-gear.

Just did a trip to Moab and it did great in the rocks. Did Hells Revenge, Fins & Things, Metal Masher, Sevenmile Rim, Elephant Hill, Top of the World, and some others and never felt even a little underpowered. In 4LO, I hit 8th gear at about 20 mph. It definitely shifts gears a lot more in 4LO after the re-gear.
Did you have to replace the carriers when moving up to 4.56 from 3.73?
 

Dasher320

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Did you have to replace the carriers when moving up to 4.56 from 3.73?
I had a shop do the re-gear. I didn’t ask and they didn’t say. I do a lot of work on the Jeeps I have, but re-gearing is over my head.
 

JL2021guy

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So they charge you for new carriers or no ? I could tell from the price as it’s usually around 2k here to gear wo carriers
Carriers prolly 4K (2k more )
 

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BuffaloBill

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I installed 4.10s about 500 miles ago and am running 315/70-17 (about 34.5”). Although this ratio change is only 10%, I appreciate the difference and personally consider it optimized.

I’ve been running the front axle on straight stretches to get some time on those gears, and note that the instantaneous mpg usually drops by 1 when front is engaged. The average reported mpg seems to be about the same as with the 3.73, even with the front axle use included.

This re-gear of course, requires no carrier change.
 

Dasher320

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So they charge you for new carriers or no ? I could tell from the price as it’s usually around 2k here to gear wo carriers
Carriers prolly 4K (2k more )
They charged $1750 so I guess no carriers. I've put about 10k miles on the new gears including towing and some rock crawling in Moab so I think they did it right.
 

xtremejoe

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I went with 4.56 on my JLURD on 37's. I do a lot of highway driving pulling a travel trailer and do a fair amount of rock crawling. I've put about 10k miles on the new gears and I like the 4.56/37 combo.

On the highway I get about 24-25 mpg not towing, about 14 mpg towing. I used to have a major issue with the engine temp rising while towing uphill--though I still watch it and it will rise on very steep passes, it has gotten better with the re-gear.

Just did a trip to Moab and it did great in the rocks. Did Hells Revenge, Fins & Things, Metal Masher, Sevenmile Rim, Elephant Hill, Top of the World, and some others and never felt even a little underpowered. In 4LO, I hit 8th gear at about 20 mph. It definitely shifts gears a lot more in 4LO after the re-gear.
Thanks for the info. Although, I have no idea how you get 25mpg unless you drive like my grandma :)
I get around 20-21 with all the upgrades (heavy machine), but stock 33 tires. Got the 37s finally this week and dropped to 17-18 (highway). Surprisingly, didn't drive too bad with 3.73 gears, but going up big hills needed to do manual override to downshift. I actually think 4.10 would be the right ratio, but will get 4.56 if going through the regear expense (On my old TJ 4.88 was the right gear for 37s, but with manual could also get away with 4.56).
 

rickinAZ

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I installed 4.10s about 500 miles ago and am running 315/70-17 (about 34.5”). Although this ratio change is only 10%, I appreciate the difference and personally consider it optimized.

I’ve been running the front axle on straight stretches to get some time on those gears, and note that the instantaneous mpg usually drops by 1 when front is engaged. The average reported mpg seems to be about the same as with the 3.73, even with the front axle use included.

This re-gear of course, requires no carrier change.
Jeep would have done well if they had offered 4.10s as a factory option (at, say, $500). Many of us would have opted for it.
 

JL2021guy

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I would think 4.10 would be the sweet spot for the diesel and 4.56 for penta
 

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40”JLURD

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Thanks for the info. Although, I have no idea how you get 25mpg unless you drive like my grandma :)
I get around 20-21 with all the upgrades (heavy machine), but stock 33 tires. Got the 37s finally this week and dropped to 17-18 (highway). Surprisingly, didn't drive too bad with 3.73 gears, but going up big hills needed to do manual override to downshift. I actually think 4.10 would be the right ratio, but will get 4.56 if going through the regear expense (On my old TJ 4.88 was the right gear for 37s, but with manual could also get away with 4.56).
Have you had a chance to re gear to 4.56 yet @xtremejoe ?

I’m thinking of going down in Ratio on mine. With 40’s and 4.88 the best I can get is 15.x MPG... horrible

I know this sounds crazy but I was thinking of going to a 4.10 or 4.56 myself. If I can find a 4.30 for the Dana Ultimate 60’s I have I will definitely get those.

My tires measure 39” and I’m quite bummed on the 15 MPG with the EcoDiesel motor. Lol
 

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Have you had a chance to re gear to 4.56 yet @xtremejoe ?

I’m thinking of going down in Ratio on mine. With 40’s and 4.88 the best I can get is 15.x MPG... horrible

I know this sounds crazy but I was thinking of going to a 4.10 or 4.56 myself. If I can find a 4.30 for the Dana Ultimate 60’s I have I will definitely get those.

My tires measure 39” and I’m quite bummed on the 15 MPG with the EcoDiesel motor. Lol
what is your average cruising speed and rpm ? We just did a trip to Monterey over the Pacheco pass average 80-85 ,still did 18mpg there and 20 back . It’s about 240 miles . I have 4.88 ,39.8 actual tire and very heavy trussed Dana 60 and 14bolt .
 

40”JLURD

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what is your average cruising speed and rpm ? We just did a trip to Monterey over the Pacheco pass average 80-85 ,still did 18mpg there and 20 back . It’s about 240 miles . I have 4.88 ,39.8 actual tire and very heavy trussed Dana 60 and 14bolt .
Highway about 70-80 probably and around 2,000 to 2,200 RPM.

2,145 RPM is 75 MPH
2,000 RPM is 70 MPH
1,850 RPM is 65 MPH

I’ve never seen 20MPG even once since adding the lift and tires. Best tank ever was 1 freak tank at like 17.4 hand calculated. Other than that never been even in the 16’s consistently.

I’m thinking the 4.88 is too low for my application and the Diesel engine
 

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I know this sounds crazy but I was thinking of going to a 4.10 or 4.56 myself. If I can find a 4.30 for the Dana Ultimate 60’s I have I will definitely get those.
Not crazy. 4.30 is what I’m thinking for 40’s. If you search Dana Super 60 4.30 R&P. Dana does make them in the 10” version. Nitro also list them as 10”. Other manufacturers/Dana will also have the more common 9.75” in 4.30.
 

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Highway about 70-80 probably and around 2,000 to 2,200 RPM.

2,145 RPM is 75 MPH
2,000 RPM is 70 MPH
1,850 RPM is 65 MPH

I’ve never seen 20MPG even once since adding the lift and tires. Best tank ever was 1 freak tank at like 17.4 hand calculated. Other than that never been even in the 16’s consistently.

I’m thinking the 4.88 is too low for my application and the Diesel engine
The plus side is that your exhaust will stay clean and oil pressure stable
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