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For those going with 37s, are you regearing??

gato

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With the 8-speed auto, 4.10 Rubi gears, lighter (e.g. KO2s) 37s and high cruise speeds, I see more downsides to regearing than upsides.

The gearing teeth are smaller and can handles less torque. You may void the warranty for things like the infamous locker sensor failure. Jeep is slightly noisier due to higher RPM if you are cruising at 75MPH.

At the other end of the spectrum, manual transmission, heavy 37s, Sport/Sahara, lower (60MPH) cruising speeds, a regear may be advantageous.

For me, if I trusted my axles to handle it, I'd have no problem running 39x13.5 BFGs with the Rubi 4.10 and A8. But everyone's driving style and preferences are different. So put the tires on, see how you like it before making any decisions. There is no set answer.
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With the 8-speed auto, 4.10 Rubi gears, lighter (e.g. KO2s) 37s and high cruise speeds, I see more downsides to regearing than upsides.

The gearing teeth are smaller and can handles less torque. You may void the warranty for things like the infamous locker sensor failure. Jeep is slightly noisier due to higher RPM if you are cruising at 75MPH.

At the other end of the spectrum, manual transmission, heavy 37s, Sport/Sahara, lower (60MPH) cruising speeds, a regear may be advantageous.

For me, if I trusted my axles to handle it, I'd have no problem running 39x13.5 BFGs with the Rubi 4.10 and A8. But everyone's driving style and preferences are different. So put the tires on, see how you like it before making any decisions. There is no set answer.
Yeah most everyone that did 40s is doing one ton axles. Yea 39s is close to to not have to do one ton axles. 38s you can probably get away without one ton axles but you're very limited on tire choices on 38s
 

JeepinJason33

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With the 8-speed auto, 4.10 Rubi gears, lighter (e.g. KO2s) 37s and high cruise speeds, I see more downsides to regearing than upsides.

The gearing teeth are smaller and can handles less torque. You may void the warranty for things like the infamous locker sensor failure. Jeep is slightly noisier due to higher RPM if you are cruising at 75MPH.

At the other end of the spectrum, manual transmission, heavy 37s, Sport/Sahara, lower (60MPH) cruising speeds, a regear may be advantageous.

For me, if I trusted my axles to handle it, I'd have no problem running 39x13.5 BFGs with the Rubi 4.10 and A8. But everyone's driving style and preferences are different. So put the tires on, see how you like it before making any decisions. There is no set answer.
Voiding the warranty depends on the dealership. That is if the mechanic even figures out there are different gears in there. The sensor did fail in my front axle immediately after the re-gear. The service department told me they did not care about the re-gear, but that I would have to pay to swap out the gears in the new axle. That would cost more than just getting the Tazer sensor fix.

At altitude, the re-gear was absolutely necessary. I did not notice any increase in noise and the RPM's are similar to before the extra weight and gears. Off-road crawling was incredible! The gearing was perfect.

It is difficult to jam a bunch of money into the 44's if you are planning on going with 60's later on. For me, 60's are in the future, but will probably wait a few years. I am already about 20k into mods on the JL and it performs very well off road.
 

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Someone told me that went the 513s that it doesn't down shift at a certain speed as good. So the way to get it at the stock is the 488s
There's a number of members here who have done a regear, but didn't reprogram for the larger tire and lower gearing. They seem to think that it's just a correct speedo that they get for the money, but don't realize that although the transmission is adaptive it still relies on being fed accurate baseline info.
 

gato

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Voiding the warranty depends on the dealership. That is if the mechanic even figures out there are different gears in there. The sensor did fail in my front axle immediately after the re-gear. The service department told me they did not care about the re-gear, but that I would have to pay to swap out the gears in the new axle. That would cost more than just getting the Tazer sensor fix.

At altitude, the re-gear was absolutely necessary.

.... I am already about 20k into mods on the JL and it performs very well off road.
Was that with the Turbo on 3.6 that you noticed the altitude degradation?

$20K of mods, ouch. You made me feel better since I'm around $8K. The issue is that the next step (D60 + 39x13 tires) is huge!
 

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Was that with the Turbo on 3.6 that you noticed the altitude degradation?

$20K of mods, ouch. You made me feel better since I'm around $8K. The issue is that the next step (D60 + 39x13 tires) is huge!
Was with the 3.6L. Originally purchased the 3.6l because I like the fact that the torque comes up with less RPM's than the 2L Turbo. I also figured I was going to supercharge it at some point, but honestly with the gear change, I don't think there will be a need for the superchager. Jumps off the line and holds 75mph in 8th gear just fine at 6,000 ft which is where I do the majority of my driving.

I sold one of my paid off Jeeps for 20k to use the proceeds for building up this one. Pretty much did everything I could dream of on this one right away. Will upgrade axles in a few years when it is time for new tires.
 

Zandcwhite

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Was with the 3.6L. Originally purchased the 3.6l because I like the fact that the torque comes up with less RPM's than the 2L Turbo. I also figured I was going to supercharge it at some point, but honestly with the gear change, I don't think there will be a need for the superchager. Jumps off the line and holds 75mph in 8th gear just fine at 6,000 ft which is where I do the majority of my driving.

I sold one of my paid off Jeeps for 20k to use the proceeds for building up this one. Pretty much did everything I could dream of on this one right away. Will upgrade axles in a few years when it is time for new tires.
Was with the 3.6L. Originally purchased the 3.6l because I like the fact that the torque comes up with less RPM's than the 2L Turbo. I also figured I was going to supercharge it at some point, but honestly with the gear change, I don't think there will be a need for the superchager. Jumps off the line and holds 75mph in 8th gear just fine at 6,000 ft which is where I do the majority of my driving.

I sold one of my paid off Jeeps for 20k to use the proceeds for building up this one. Pretty much did everything I could dream of on this one right away. Will upgrade axles in a few years when it is time for new tires.
While technically the 3.6L torque comes on at lower rpms, it gets destroyed in that department in every real world driving condition/rpm range by literally every other engine available in a JL. By 2,100 rpms the 2.0 is flying right past the 3.6L torque output. That's literally less than 1/10th of a second after leaving a stop sign or hitting the throttle on an obstacle. By 3,500 rpms the 2.0L is up by 75 ftlbs at the wheels. The only place the 3.6L beats the turbo is above 5,700 rpms, but who runs those kind of rpms in a jeep anyway? As far as power under the curve and real world driving, it's not even close.
Jeep Wrangler JL For those going with 37s, are you regearing?? 20v36_torque-
 

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While technically the 3.6L torque comes on at lower rpms, it gets destroyed in that department in every real world driving condition/rpm range by literally every other engine available in a JL. By 2,100 rpms the 2.0 is flying right past the 3.6L torque output. That's literally less than 1/10th of a second after leaving a stop sign or hitting the throttle on an obstacle. By 3,500 rpms the 2.0L is up by 75 ftlbs at the wheels. The only place the 3.6L beats the turbo is above 5,700 rpms, but who runs those kind of rpms in a jeep anyway? As far as power under the curve and real world driving, it's not even close.
Jeep Wrangler JL For those going with 37s, are you regearing?? 20v36_torque-
Thanks for the graph. It is similar to the others I have seen showing that "technically?" the 3.6 torque does come on at lower RPMs. I bought the JLUR for my version of real world driving which is trails every weekend. I did not want to hit 2,100 RPM's all the time. Running the same exact obstacles over several trips with guys running 2.0 turbo's I have seen them have to rev it up higher to get the torque to get up. In many cases, not being able to crawl up like I was. Could be several other factors, like driver ability, tires, lift, or whatever. To me, it seemed like a torque issue.

Not debating which is a better engine. I think it depends on the driver and what they are using it for. The 3.6l is the one I initially wanted due to the ability to run a supercharger if needed. Right now the supercharger options are not great as they are having problems getting the tune right. Eventually they will figure it out. However, I have been very happy with the 3.6l and don't feel like the supercharger is as needed as it was on my 4.0l TJ.
 

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If you do a lot of road trips, and tend to drive 85mph+, you are better off with 4.10's in my opinion. When we are cruising 1,200 miles out to moab at ~90mph we are seeing 2,200 rpms in 8th gear, which it holds no problem at that speed. If we went to 5.13's, it would be closer to 2,900 rpms. With the 4.7:1 1st gear and the 4:1 transfer case, there's plenty of gearing in low range regardless of tire size. If you tend to drive 80+, I wouldn't go below 4.56 if I were choosing gears (4.59 is the equivalent ratio of 4.10's with 33's versus 37's anyway). I definitely wouldn't waste the money on a regear to go from 4.10's to 4.56 so I'm staying where I'm at.
Since you also live in CA and probably see some varied terrain, I'd like to find out the specs on your Jeep. I've got a 3.6l JLUR with the automatic and I'm debating between 35 and 37 inch BFG KO2s. They don't weigh that much so I'm wondering if the 3.6l can turn them without regearing. If you have the turbo, that changes things. Thank you.
 

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Since you also live in CA and probably see some varied terrain, I'd like to find out the specs on your Jeep. I've got a 3.6l JLUR with the automatic and I'm debating between 35 and 37 inch BFG KO2s. They don't weigh that much so I'm wondering if the 3.6l can turn them without regearing. If you have the turbo, that changes things. Thank you.
2.0t, pretty heavy geolander x-mt's, steel bumpers, winch, hi-lift, 200+ lbs worth of tools/compressor/recovery gear in the Jeep at all times. If you kept the weight down I think the 3.6L would be fine. The 8 speed does a great job of keeping the engine in it's power band. I think people make way to big of a deal about 8th gear anyway. If you're spending more time in 8th gear because you are always at a higher rpm, are you really gaining anything? Even 7th gear is still an overdrive, and I'm far more concerned with the rpm range cruising at freeway speed than the gear the transmission is in. Even if you only see 8th on downhills like some claim, you are still at lower rpms in those scenarios than the guys with 4.88s will ever see at speed.
 

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Only every now and mine won't hit 7th or 8th I use manual overdrive and do it myself then when I come out of it and I need it again it will automatically do it itself and I hit 7th and eighth very rare will not do it on its own and I have 37s with 410s. I was told 488 s is more closer to stock than 5:13 513s will be low geared. But everyone has their own opinion this is coming from a good friend of mine that's a mechanic that has done many of these. more people are happy with the 488 he said it feels more like stock to them and he agrees. But for everyone that says they like 488 you'll find somebody saying they like the the 513s. But I'm perfectly fine with my 410's I'm heading 7th and 8th lost all the time and every now and when it doesn't I'll just click it over and do it myself I'll save my 1800. And yes I've been recalibrated to 37s with a tazer that I have
 

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At altitude, the re-gear was absolutely necessary. I did not notice any increase in noise and the RPM's are similar to before the extra weight and gears. Off-road crawling was incredible! The gearing was perfect.
On what planet are the rpms similar between 4.10's and 5.13's? Weight has 0 effect on rpms. It's gearing and tire size period. Simple math. A stock Rubicon at 80 mph is turning 2200 rpm, you're turning 2500 rpms at the same speed. If we are rolling 90 across Utah, stock Rubicon is spinning 2500rpm, you're at 2800+, and my 4.10's and 37's...2245. I could regear, and be forced to slow down, but I'll pass.
 
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JeepinJason33

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On what planet are the rpms similar between 4.10's and 5.13's? Weight has 0 effect on rpms. It's gearing and tire size period. Simple math. A stock Rubicon at 80 mph is turning 2200 rpm, you're turning 2500 rpms at the same speed. If we are rolling 90 across Utah, stock Rubicon is spinning 2500rpm, you're at 2800+, and my 4.10's and 37's...2245. I could regear, and be forced to slow down, but I'll pass.
Original tires were 33's and I went with 39's and I said similar, not the same... Simple math dictates this fact; in order to cover the same amount of ground, a small tire must rotate more times than a larger tire. Because of this, the taller the tire, the faster it propels the vehicle, even as the vehicle's engine produces the same number of rotations per minute (RPM). My RPM's are very close with the gear set up and increased tire size take a look at the calculator below from the Spicer page. The JL has 8 gears so the Overdrive is the number that would be closest. Not sure where you are getting your info from...
Jeep Wrangler JL For those going with 37s, are you regearing?? Stock.PNG

Jeep Wrangler JL For those going with 37s, are you regearing?? 39.PNG
 

Zandcwhite

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Original tires were 33's and I went with 39's and I said similar, not the same... Simple math dictates this fact; in order to cover the same amount of ground, a small tire must rotate more times than a larger tire. Because of this, the taller the tire, the faster it propels the vehicle, even as the vehicle's engine produces the same number of rotations per minute (RPM). My RPM's are very close with the gear set up and increased tire size take a look at the calculator below from the Spicer page. The JL has 8 gears so the Overdrive is the number that would be closest. Not sure where you are getting your info from...
Jeep Wrangler JL For those going with 37s, are you regearing?? 39.PNG

Jeep Wrangler JL For those going with 37s, are you regearing?? 39.PNG
http://www.grimmjeeper.com/gears.html
Just the actual numbers for a jl 8 speed auto, nvg241or tcase, gears, and tires factored in with the ability to check rpm at any speed, but I'm sure your generic estimates from Spicer are more accurate. I did use 37's, so your rpms will be slightly lower with the 39's. At 90mph you'll still be spinning 2665rpm, higher than where I want to be in top gear but that's just my opinion.
 

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http://www.grimmjeeper.com/gears.html
Just the actual numbers for a jl 8 speed auto, nvg241or tcase, gears, and tires factored in with the ability to check rpm at any speed, but I'm sure your generic estimates from Spicer are more accurate. I did use 37's, so your rpms will be slightly lower with the 39's. At 90mph you'll still be spinning 2665rpm, higher than where I want to be in top gear but that's just my opinion.
I guess I am on the right planet then? I have re-geared at least 11 of the Jeeps I have owned and track the difference pretty closely. For the last few, I have a stretch of freeway that I drive everyday at 75 mph (which is the posted speed limit here on most of the freeways in Colorado). For the JL, 8th gear held the same in the same spots and shifted down in almost the exact same spot stock as it did with the gear and bigger tire change. I don't drive much faster than 80 mph in the Jeep. Certainly don't hit 90 mph at altitude very often if ever, not really what I bought the Jeep for. I bought it to spend the majority of the time off road and the gearing certainly helped there.
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