37s and drivetrain reliability - is it worth it?

hjdca

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Synergy HD Adjustable Ball Joint Kit has new adjustable, serviceable ball joints without re-pressing them out and in again. They are already available for the JK, but, not the JL and JT yet... I think...
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PCOIP

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I have a 2021 JTR with Mopar 2In lift and 35s on 17s. No regearing - stock Rubicon gears. 6MT. I debate going to 37s. I could do it with no further suspension mods. But I would definitely want to regear. 35s is bad enough with the 6MT and I am pretty sure 37s would be horrible. What I'm concerned about is drivetrain reliability. I don't rockcrawl but I do hund and drive on muddy and heavily rutted logging roads. Axle and differential clearance is what I'm looking for. I know 37s only give me another inch... But I worry about stress on axles and hubs. And about braking capability with so much added rotating mass. Jeep seems to treat 35s as clearly within factory tolerances for (e.g. extreme recon package ith 35s will be tires and gears but no changes to brakes and axle parts).

What is your experience with 37s - drivability and reliability? Is it really a big difference over 35s? So far I think 35s strike a great balance between reliability, warranty-ability, and overall good looks.

I'm sure this opinion has been debated but now that people have put 30-40K miles potentially on 37s I'm curious about long term livability.

Thanks
I have 37’s but I’d seriously consider going to Nitto 38x17s which are a new tire size. I went from the stock 33’s to 37x20s. My Rubicon had good clearance with 37s no rubbing without a lift & looked nice. My MPGs went down to 13 MPG. It would just rev & get stuck in gear when passing or starting off the line etc. it had no pep wouldn’t shift correctly. I decided to regear from 4.10s to 5.13s, which was the best decision I made. I get better MPG’s with 37s than stock I get around 16-16.5 MPGs around town at Altitude. I ended up lifting it anyway with a JKS J-Venture 3-3.5” Lift at the same time which improved the steering immensely, way better than stock. The ride is just as good or slightly better than stock even with Nitto M/T tires. I don’t hear them much at all. These Nitto TG’s are known for their good ride quality in an M/T tire. The wind doesn’t bother my Gladiator anymore or passing semi trucks. It looks good, I had someone wait for me at my vehicle to ask me about my lift for his gladiator recently. Hope this helps!
 
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Snowcavemike

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I have a 2021 JTR with Mopar 2In lift and 35s on 17s. No regearing - stock Rubicon gears. 6MT. I debate going to 37s. I could do it with no further suspension mods. But I would definitely want to regear. 35s is bad enough with the 6MT and I am pretty sure 37s would be horrible. What I'm concerned about is drivetrain reliability. I don't rockcrawl but I do hund and drive on muddy and heavily rutted logging roads. Axle and differential clearance is what I'm looking for. I know 37s only give me another inch... But I worry about stress on axles and hubs. And about braking capability with so much added rotating mass. Jeep seems to treat 35s as clearly within factory tolerances for (e.g. extreme recon package ith 35s will be tires and gears but no changes to brakes and axle parts).

What is your experience with 37s - drivability and reliability? Is it really a big difference over 35s? So far I think 35s strike a great balance between reliability, warranty-ability, and overall good looks.

I'm sure this opinion has been debated but now that people have put 30-40K miles potentially on 37s I'm curious about long term livability.

Thanks
OMG. my Diesel Gladiator dives like a dream on 37's. get the falcon 2 steering stabilizer. Because of the Diesel, factory 3.73 works. the factory axles on the max tow and Rubicon are made to handle the big tires. you need to upgrade the steering components. I use Smart Steer and a steering box stabilizer. handles in the rough stuff like a Cadillac. if you are planning rock crawling, upgraded axels are recomended.
20211102_112743.jpg
 

GusGus

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OMG. my Diesel Gladiator dives like a dream on 37's. get the falcon 2 steering stabilizer. Because of the Diesel, factory 3.73 works. the factory axles on the max tow and Rubicon are made to handle the big tires. you need to upgrade the steering components. I use Smart Steer and a steering box stabilizer. handles in the rough stuff like a Cadillac. if you are planning rock crawling, upgraded axels are recomended.
20211102_112743.jpg
Are the axles different on the Willys Sport or Willys compared to the Rubi?
 

WesMills7

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i was running the stock sport gears 3.73 :puke: . The great, the vehicle pretty much jumps to 4th gear in the first 200 feet, it feels weightless, and accelerates like it has a turbo in it (2021 Willys), and gets about 20 miles a gallon (at 55mph) with a full teraflex 3.5 inch lift that has all 8 adjustable control arms, track bars, and falcon 3.3 shocks,. Additionally, I have a rebel summit front bumper with 10k winch, and trail rax rack on the back= a lot more weight than factory. The downside, expect low gear noise, not annoying or noticeable but you hear it a little with your windows down. Youll also have lower mpg on highway.
This is actually great information. Thank you for sharing. Been really debating 4.88s and 5.13s. You said 20 mpg at 55mph which is incredible. I get about 16-16.5mpg at that speed with 4.10s. What do you get for mpg on the highway?

The fact that it jumps right into 4th is another HUGE plus. I don’t drive crazy and I ease into the gas pedal when accelerating, but my jeep hangs out in 1st and 2nd wayyy to long to the point where I feel like it could cause long-term damage. How does it do going up hills?

Last questions for you haha… do you have any experience towing? Not sure what axles you have, but I’m running the stock ones that came with the max tow package. Was wondering how well you can tow with the lift, tire, and gear setup you have. Thanks!!
 

exfil offroad

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This is actually great information. Thank you for sharing. Been really debating 4.88s and 5.13s. You said 20 mpg at 55mph which is incredible. I get about 16-16.5mpg at that speed with 4.10s. What do you get for mpg on the highway?

The fact that it jumps right into 4th is another HUGE plus. I don’t drive crazy and I ease into the gas pedal when accelerating, but my jeep hangs out in 1st and 2nd wayyy to long to the point where I feel like it could cause long-term damage. How does it do going up hills?

Last questions for you haha… do you have any experience towing? Not sure what axles you have, but I’m running the stock ones that came with the max tow package. Was wondering how well you can tow with the lift, tire, and gear setup you have. Thanks!!
downside is highway driving, pushes me down to 15-16 mpg, sometimes 17 mpg. The gears allow it to climb like its driving on flat ground with no lag and or dropping out of 7th 8th gear, its great. I drive pretty aggressively, and its super responsive. Still don't regret it at all. On top of that off-roading is like cheating now. The gear just climb with little skill, no dropping to low and hardly ever even need to use 4 hi. Im not rock crawling but who is with a gladiator? I built mine for overlanding and have zero doubt that it can get anywhere I need it to. I have a good amount of towing experience. The gears will help with towing, again, making it feel like nothing is behind you. Your downside on this is really just highway speeds with MPG. Also im currently on KO2 315's (35's)with plans to replace those shoes when they run out with 37's, and I have the dana 44 axles on it. Not the "max tow" but it is interesting, I measured the axles on my gladiator and they are longer than the dana 44's on my JL Rubicon.
 
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I can assure you that's not how braking works. I don't think this is the place for an engineering discussion but if you can reliably lock up your brakes, you don't need larger brakes for clamping force.
20 years of driving fast cars confirms what you say. Bigger brakes is about fade resistance and consistency, not stopping distance... unless of course you compare a completely red hot fading rotor to a cooled off one. If an 11" cold rotor and 2 piston cold caliper can lock up a wheel, a 15" 6 piston setup will not stop the car any shorter, it will just consistently stop it at that distance when heated up while the 11" fades and stopping distances grow.
 

Mac

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20 years of driving fast cars confirms what you say. Bigger brakes is about fade resistance and consistency, not stopping distance... unless of course you compare a completely red hot fading rotor to a cooled off one. If an 11" cold rotor and 2 piston cold caliper can lock up a wheel, a 15" 6 piston setup will not stop the car any shorter, it will just consistently stop it at that distance when heated up while the 11" fades and stopping distances grow.
Talking about Jeeps with larger diameter heavier wheels and tires not fast cars, there is plenty of actual tests explaining the impact of larger tires and how larger brakes make a difference in stopping distance.
 

ecidiego

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Talking about Jeeps with larger diameter heavier wheels and tires not fast cars, there is plenty of actual tests explaining the impact of larger tires and how larger brakes make a difference in stopping distance.
Only if the smaller brakes can't lock up the wheels. The articles you read are most likely concerning brake fade down grades etc.
 

CerOf

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Talking about Jeeps with larger diameter heavier wheels and tires not fast cars, there is plenty of actual tests explaining the impact of larger tires and how larger brakes make a difference in stopping distance.
Other than the JK, what tests?

The JK’s brakes could not reliably lock up on my ‘09 JKUR. For that application, more clamping force is needed.

For the JT, a big brake kit will do nothing for me with 35s

if I go up in tire size to the point I can’t get lock up, then something more is needed.
 

CerOf

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Only if the smaller brakes can't lock up the wheels. The articles you read are most likely concerning brake fade down grades etc.
He posted a test about the JK, before. I believe. my JK’s brakes wouldn’t totally lock up with 35’s and all the weight I added. My JT’s brakes are larger, better, and easily lock up.
 

ecidiego

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He posted a test about the JK, before. I believe. my JK’s brakes wouldn’t totally lock up with 35’s and all the weight I added. My JT’s brakes are larger, better, and easily lock up.
Yep, if the brakes can't lock, certainly a brake upgrade will help.
 

ecidiego

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It's physics.

https://www.autos.com/aftermarket-parts/why-a-big-brake-kit-wont-make-your-car-stop-faster

A "test I saw on the Internet" can't disprove physics.

Physics said:
The Physics Behind Stopping.
Physics said:
Physics doesn’t discriminate between starting or stopping, but instead considers them both changes in kinetic energy. Thus, an object at a constant speed reacts the same as an object that is sitting still. That being said, the Standard Kinetic Friction Equation applies to stopping just as much as starting movement. In simple terms it says an object in contact with the ground will absorb the most kinetic energy right before movement, or sliding. This applies in the reverse as well: an car in motion will absorb the most kinetic energy right before the wheels lock up. With respect to modern vehicles, this equation states that the only way to make a car stop quicker is to either increase the coefficient of friction with the road, (e.g. upgraded tires) or decrease mass by lightening the vehicle. Note, both of these things have little to do with brakes.

Why Big Brakes Don’t Reduce Stopping Distance.
As the physics lesson states, under braking, your car absorbs the most kinetic energy (movement) right before the tires lock up. This is true for both non-ABS cars and ones equipped with ABS. Abs shortens stopping distance by attempting to keep the brakes on the point of locking- where most kinetic energy is absorbed. Even though they have come a long way, even the most advanced ABS systems react by pulsing braking pressure resulting in a slide, roll, slide, roll pattern. In a perfect world, a perfect ABS system would perch the brakes at the cusp of sliding without ever actually locking up. Upgraded calipers and rotors in a big brake kit will result in more braking torque, the stopping force applied to the wheels. This will bring about wheel lockup or ABS intervention sooner than with the stock system. This should not be interpreted as a shorter stopping distance. In many instances the larger brakes confuse the stock ABS system which is not tuned to the different pressures required to engage and disengage the brakes.

What a Big Brake System Does to Improve Performance.
Big brake systems were not designed to stop your car sooner, but rather, stop it more efficiently and consistently. The larger calipers, vented discs, and exotic-compound pads increase heat capacity and heat dissipation. These upgraded braking systems not only perform well under extreme temperatures, but in most cases perform better when hot as opposed to average street driving temperatures. This is definitely something to consider when deciding on rotor and pad compounds. Because these brakes dissipate heat more effectively, they reduce brake fade. Brake fade occurs under high temperatures, can be caused by boiled brake fluid, and results in a soft pedal and elongated stopping distances. Big brake systems don’t decrease your car’s stopping distance over stock. Instead, they are designed to perform consistently under extreme conditions so that your car will stop just as well the first time as the N’th time.
 
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