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Rubicon Diesel with 37s

DesertDog

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I would love to hear from real world, actual experiences from anyone running a Rubicon diesel with 37‘s....

particularly, I would love to hear what it’s like before re-gearing. It seems like when this discussion develops lots of opinions get thrown out by those burning gasoline which is really irrelevant.

Rubicon 3.71 gears 37s powered by a DIESEL!
If you actually have experience, let’s hear about it.

I would like to avoid thread creep here. Obviously there has been extensive discussion on running the Pentastar on 37’s and all the opinions on gear ratios.
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Davekayc

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Diesel on 37s , i had an 09 rubi with 513s with these wheels and tires. This would eat it.
Jeep Gladiator Rubicon Diesel with 37s C6DFBD38-4550-442C-8A33-FE6BAB9A4A05

Stock drivetrain , i plan on doing all the same things i did before.
 

Davekayc

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^^ the diesel with 8 speed is fine as is on 37s. I plan on doing some very scenic wheeling this year. Such as whipsaw trail again.
 

n8leav

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Just posted this on another post, but I literally just drove from Phoenix to Southern Utah going through Flagstaff. If you don't know this route, Flagstaff is about 7,000 feet above sea level, so lots of uphill travel and back down to around 3,000 feet in St George. I averaged 24 mpg there and 26 mpg on the way back home. Was easily keeping the 75 speed limit and didn't feel it struggle at all. I've also already taken it on some great trails in Sedona/Phoenix and it was awesome. As far as power/torque, I feel that it is more than efficient, and don't feel any need for a re-gear. The cost is a non-issue for me, so I would do it if I felt it was even remotely necessary. Just my 2 cents.
 

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DesertDog

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Diesel on 37s , i had an 09 rubi with 513s with these wheels and tires. This would eat it.
Jeep Gladiator Rubicon Diesel with 37s C6DFBD38-4550-442C-8A33-FE6BAB9A4A05

Stock drivetrain , i plan on doing all the same things i did before.
Are you saying that you would go to the same places as you did with your ‘09 Rubicon? Or are you saying you would do the 5.13 gears again?

thanks.
 

Davekayc

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I would go same places. Do same things . Problem with the gladiators is how much the rear sticks out. Hitch touches on even the easiest of trails. Climb any gravel pile at natural angle of repose and youll see .
the diesel has torque at such low rpm its gonna make crawling the best thing ever.
going to a higher ratio is also a weaker gear smaller , smaller pinion less bite on the crown . I will try stock wholeheartedly before i let anyone put a wrench on my factory sealed diffs. I will report my findings mid july. Hehe .
 
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DesertDog

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I would go same places. Do same things . Problem with the gladiators is how much the rear sticks out. Hitch touches on even the easiest of trails. Climb any gravel pile at natural angle of repose and youll see .
the diesel has torque at such low rpm its gonna make crawling the best thing ever.
going to a higher ratio is also a weaker gear smaller , smaller pinion less bite on the crown . I will try stock wholeheartedly before i let anyone put a wrench on my factory sealed diffs. I will report my findings mid july. Hehe .
That’s really good information. Thank you.
 

iadslgladiator

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I've clocked a little over 9k miles on 37's and stock gears. The last 3k was a road trip from iowa to Florida for spring break, 2k with a 25' panga center console in tow.

Boat and trailer around 5k lbs with a big bow sticking up in the wind. It ran low to mid 70's in 7th gear most of the time (about 2000 rpms). Running into a head wind made a noticable difference and caused an occasional downshift to 6th. Fuel mileage sucked (right around 12 mpg) DEF fluid usage was more than I anticipated (about 3 gallons/1k miles). Not what I was hoping but definitely not a total disappointment either. After pulling with many gasser jeeps over the years I can tell you none of them could touch what this one did especially on 37's and stock gears.

As I dont pull a lot I still don't see a real NEED to regear. Daily driving is perfect with the 3.73's IMO. I personally think aerodynamics and wind resistance is the biggest thing holding back highway speed performance and fuel mileage.....well that and all the emissions bullshit. If they would let these things breath and exhale they would be so much more efficient.

That said, If I was pulling anything bigger/heavier with more wind resistance, and/or running at high altitude, on a regular basis I would regear probably only to 4.10's though. I think 4.56's would be over kill and require way too many rpms to run at highway speeds.

Jeep Gladiator Rubicon Diesel with 37s 20210316_143939


Jeep Gladiator Rubicon Diesel with 37s 20210316_143855
 

Kole Miller

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I would love to hear from real world, actual experiences from anyone running a Rubicon diesel with 37‘s....

particularly, I would love to hear what it’s like before re-gearing. It seems like when this discussion develops lots of opinions get thrown out by those burning gasoline which is really irrelevant.

Rubicon 3.71 gears 37s powered by a DIESEL!
If you actually have experience, let’s hear about it.

I would like to avoid thread creep here. Obviously there has been extensive discussion on running the Pentastar on 37’s and all the opinions on gear ratios.
I have a 2021 jt gladiator rubicon on 37 nitto ridge grapplers on stock gearing . I have no plans on regearing. On my stock 33 tires i could go anywhere on the NYS thruway at 65 mph and she would stay in 8th gear no matter the hill. Now i have 37 s and a bed rack and HEO HARDSHELL TENT and now she drops into 7 th gear on many hills. Just pilled a snow mobile trailer with one sled about 1500 to 2000 pounds and she new it but always at low rpms. I personally enjoy making my diesel work hard on 37s because diesels love to work and i am not always towing.
 

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I've clocked a little over 9k miles on 37's and stock gears. The last 3k was a road trip from iowa to Florida for spring break, 2k with a 25' panga center console in tow.

Boat and trailer around 5k lbs with a big bow sticking up in the wind. It ran low to mid 70's in 7th gear most of the time (about 2000 rpms). Running into a head wind made a noticable difference and caused an occasional downshift to 6th. Fuel mileage sucked (right around 12 mpg) DEF fluid usage was more than I anticipated (about 3 gallons/1k miles). Not what I was hoping but definitely not a total disappointment either. After pulling with many gasser jeeps over the years I can tell you none of them could touch what this one did especially on 37's and stock gears.

As I dont pull a lot I still don't see a real NEED to regear. Daily driving is perfect with the 3.73's IMO. I personally think aerodynamics and wind resistance is the biggest thing holding back highway speed performance and fuel mileage.....well that and all the emissions bullshit. If they would let these things breath and exhale they would be so much more efficient.

That said, If I was pulling anything bigger/heavier with more wind resistance, and/or running at high altitude, on a regular basis I would regear probably only to 4.10's though. I think 4.56's would be over kill and require way too many rpms to run at highway speeds.

The mini van motor gets that with 37's not towing and most full size trucks would get similar or worse when towing that boat. So it really only sucks cause your accustomed to getting such good fuel mileage unloaded, but in the grand scheme of things its not bad at all imo.
 

iadslgladiator

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The mini van motor gets that with 37's not towing and most full size trucks would get similar or worse when towing that boat. So it really only sucks cause your accustomed to getting such good fuel mileage unloaded, but in the grand scheme of things its not bad at all imo.
Agreed........... was just hoping to go more than 200ish miles without needing to stop for fuel.
 

Davekayc

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I mean rather than have a commonplace specification there they could have easily made it a major appeal point. With little trade off . Still love it though.
 

BEERviper

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I would love to hear from real world, actual experiences from anyone running a Rubicon diesel with 37‘s....

particularly, I would love to hear what it’s like before re-gearing. It seems like when this discussion develops lots of opinions get thrown out by those burning gasoline which is really irrelevant.

Rubicon 3.71 gears 37s powered by a DIESEL!
If you actually have experience, let’s hear about it.

I would like to avoid thread creep here. Obviously there has been extensive discussion on running the Pentastar on 37’s and all the opinions on gear ratios.
I'm going to jump in on this one even though my diesel is a Sport S. Other than the lockers (more weight), 4:1 transfer case and higher front fenders everything else is the same.

My Sport S diesel has the same 3.73:1 rear end gear ratio and I'm running 37" BFG KO2's on Mopar beadlock wheels.

I can tell you for certain as it stands right now, I see ZERO reason to regear. It holds 8th gear just fine at highway speeds. I just returned from a 200 mile drive from NW Denver (~5k feet) up to the mountains to ski crossing ~11k feet and back and averaged ~25mpg on that trip. The diesel just LOVES to pull, and the altitude seems rendered irrelevant with BOOST!

I will be towing in the Spring (18' camper ~3,500lbs) which will be the decision maker ultimately, but my thoughts right now are who cares if I have to tow in 6th gear most of the time and only see 7th/8th on flat or down hills. As long as it isn't damaging to the drivetrain, my plan is to stick with stock gears.

That said, If I was pulling anything bigger/heavier with more wind resistance, and/or running at high altitude, on a regular basis I would regear probably only to 4.10's though. I think 4.56's would be over kill and require way too many rpms to run at highway speeds.
I would tend to agree here, 37's on the 3.73 gears just seems so perfect. On the Sport S the stock tire size was 31.5" and I felt like the 3.73 was too big of a gear, now with the 37's it's just right.

If towing is that much of an issue with the 3.73 gear I don't think I would go bigger than 4:10, especially considering my dealer would likely do the install and warranty it along with the rest of the drivetrain and suspension that they installed.
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