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

[Pescatoral Pursuit]

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

Except for maybe axle strain, tall tires and high ratios cancel each other out, no?
I find my 37 KO2s on factory gearing shift too fast on light acceleration, okay during heavy acceleration at lower speeds, and too slow for heavy acceleration at higher speeds.

Low range in Moab has also been fine with 3.73s IMHO.

You can thank the Rubicon TC for that. In all likelihood when I regear I'll also look to trade for a Sport/ Overland TC.

unlike the 392, most people arent going to hoon their turbodiesel like a brodozer.

Spock, are you outta your Vulcan mind?! What else are you supposed to do w 500lbft of torque? Ceramic coat the paint?

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[ACAD_Cowboy]

Except for maybe axle strain, tall tires and high ratios cancel each other out, no?

Spock, are you outta your Vulcan mind?! What else are you supposed to do w 500lbft of torque? Ceramic coat the paint?

A. Higher ratio is numerically lower, 2.08 axles would give screaming high speed and damn near dead rpm at highway cruise.

B. I'll assume you are the guy all kitted for overland but the truck is always spotless and shiny.

 

[Pescatoral Pursuit]

A. Higher ratio is numerically lower, 2.08 axles would give screaming high speed and damn near dead rpm at highway cruise.

Try again silly.

 

[CrazyCooter]

Try again silly.

Uhhhhh He is correct? Did you misread the post?

 

[ACAD_Cowboy]

Try again silly.

So...

The "ratio" being discussed is the ratio of input revolution of the gear set to output revolutions.

A high ratio of inputs to outputs has less inputs for one output versus a low ration which has more. We tend to to describe "high" gears as being numerically smaller or lower and vice versa which is why I made great pains to include those terms to help aid the discussion.

My first car was equipped with a 307, a powerglide and and a 2.56:1 final drive gear ratio. I was gifted a 4.88 limited slip that came with a 350 and th350 and while trying to resolve some complications a buddy coughed up a lincoln locked axle that he thought had some stupid ratio... he was right... 2.08 from a 194 turbothrift station wagon... no acceleration to speak of but it was good for a 156mph flying mile. I beat the 5 liter mustang becaue he ran out of rpm while I was still somehow making power.

Point being, if we were truely looking for high mpg we would all e moving the other way ratio was and not trying to restore the felt or apparent torque. But then our rigs would suck offroad.

So to recap, higher ratios are numerically lower and vice versa.

 

[Pescatoral Pursuit]

A high ratio of inputs to outputs has less inputs for one output versus a low ration which has more.

You are out of your Vulcan mind, lol.

I know you have some grasp on what you are trying to convey but in your effort to be a smartass about it you've messed it all up.

 

[ACAD_Cowboy]

Sigh...

Look, it's cool. I get it. But what you need to remember is it's not just you, there are plenty of people on the forum who have never owned any real 4wd before, never really thought about all the math and science and physics behind going and playing in the dirt. My attempt to educate is focused broadly and designed to stimulate questions and responces as aids to learning and exploration.

I'm am also older and wiser than I once was and have learned that being correct is generally better than being right. We can go round and round on possibly any topic related to jeeping, offroading, overlanding, rock crawling, towing, hauling, tuning, economy etc and if we ask 12 forum members we will likely get at least 13 opinions. I can go the distance myself and can dial the snark well beyond 11 but really it stops being fun after a while, more like sad wack'a'mole. I don't want that and I feel like you don't either.

So to recap, water is wet, fire is hot, the sky is blue and while the diesel can make the power to cover the lack of gearing, it wouldn't hurt to plan for a regear in the future. Your mileage may vary.

 

[Robbys3m3]

40s

 

[@californiajeeping]

I love people trying to calculate and overthink things when in the real world the difference is so minuscule it doesn’t even matter.

I’d run 40s on a ecodiesel without regearing. If anything it just needs more power.

 

[Jeepasaurus_Rex]

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

Alright, well my trip ended up being about 4,400 miles overall. A pretty solid mixture of highway, city, construction zones, idling in traffic, idling in camp, off-roading/crawling, forest roads and general exploring. Massive terrain/elevation changes throughout the entirety of the trip. I averaged 19.5mpg for all of it. Saw as high as 22mpg, and as low as 16.8mpg active averages. Everything calculated by the dash, not by hand (too much to do haha).

8th gear still existed, but for the most part it seemed better suited in 7th.

Stock 3.73 gears. 40" Cooper STT Pros. And a bunch of weight (she's real thiccc back there).
Banks Pedal Monster set to City #7.

All of this being said, would I regear? Yes.
Do I feel like I NEED to regear... nah not really.

I'm going to look into getting 4.10's, but it isnt much of a concern. With the Pedal Monster set to City #7, it has plenty of power for what I need, and feels better than stock.

Hope this helps

 

[NCJL]

I’m on 40” Yokohama X-MT’s with 5.13 gearing. I geared for 42’s that I couldn’t get in time for the build. 40’s should be 4.88 gearing. The 5.13 is ok with 40’s, better with 42’s.

If fuel mileage is a gage: I’m heavy, close to 7K on the CAT scale.
I currently average 21 MPG mixed driving. 22 MPG highway with grades.

My wife driving the JTRD from Laughlin to Los Alamos following the Uhaul with trailer got 28 MPG. She is very light footed. Said 58mph was the sweet spot.

Yes GPS verified speedo and confirmed with quick math to confirm.

 

[CrazyCooter]

Funny how opinions on gearing is so subjective........

I loved the 3.73's on 37's all around except for the heaviest of wind resistant loads (Travel trailer with motorcycle in the bed) where the truck might struggle to stay in 6th with a light headwind at 60ish mph.

I then swapped 4.10's knowing that a 10% change would be too much, but no gears available in between. I HATED IT with 4.10's and 37's with it getting 3-4 gears before clearing an intersection! I also noticed what seemed like the ECU pulling throttle out while climbing moderate hills? I had however already planned to jump up to 38's which is about 3%, so that offset would be more like 7%.

I swapped on the 38's a couple of weeks ago and I like it again......gear spacing seems to be perfect. I have yet to tow, but it has to be better than before the gear swap and the last 350 mile trip I took in the mountains netted us 24mpg!

I saw Nate (Dirt Lifestyle) swapped 5.38's for his smallish BFG 39's and thought to myself WTF? Some people are obsessed with pulling 8th going uphill, but I'd rather save 8th for when it's flat unloaded.

I would like to 4.30's for 40's

 

[Trout Safari]

I was running 35's with a pretty good lift and I could feel the difference from stock. When I was towing a Turtleback trailer at times it word be shifting back and forth between gears quickly. There is no doubt even with the 35's I needed to re-gear. This week I am installing 37" tires and I am re-gearing to 4:56.

 

[NCJL]

I also was strongly considering 4.30 for 40” tires in the early stages of of my build when I had the JLURD. After a lot researching I decided 4.88 would be best. Switched to the JTRD and 5.13 for 42”.

AEV had some solid info on their website regarding this. They use 4.56 with 37” tires with ED and gasser.

I came to the conclusion that keeping close to factory specs with gearing was important. I also drove a JTRD with 5.38 and 42” on long trip. Little to low for me, however it was good. The owner loved it.

End of day I think we all have many good gearing options with the ED. Its personal preference. Most choices can be justified.

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