Gears for 37" tires

[KurtP]

For 37’s on the 8spd; 4.56 is the equivalent gear to stock. 4.88 is one step, 5.13 is two steps.

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[FLUndertaker]

For 37’s on the 8spd; 4.56 is the equivalent gear to stock. 4.88 is one step, 5.13 is two steps.

Equivelant to factory 373 or 410?

 

[KurtP]

Equivelant to factory 373 or 410?

37->4.56 = 33->4.10

(New tire size x stock gear ratio) / stock tire size = equivalent to stock new ratio

 

[FLUndertaker]

37->4.56 = 33->4.10

(New tire size x stock gear ratio) / stock tire size = equivalent to stock new ratio

So ....

(36*4.1)/31.5= 4.68 to get me back to stock.

4.88 looks like the obvious choice since they are a bit lower than stock once calculated for my 37” Nittos. I just wonder if the 5.13 would give me a little more off the line and down low plus for occasional towing. Would hwy driving at 80 with 5.13 still be reasonable?

 

[KurtP]

So ....

(36*4.1)/31.5= 4.68 to get me back to stock.

4.88 looks like the obvious choice since they are a bit lower than stock once calculated for my 37” Nittos. I just wonder if the 5.13 would give me a little more off the line and down low plus for occasional towing. Would hwy driving at 80 with 5.13 still be reasonable?

Yeah that sounds right. In MY opinion, driving 80 with 5.13 would be too buzzy, but I rarely drive that fast, and in reality its only about another 150rpms. I was swayed towards 4.88’s after talking at length with another forum member buying my stock wheels who has a tricked out Glad, 37‘s, 4.88 and tows a camper. He said it was perfect, although i have no personal experience towing with this truck yet. I think if I was towing, I would lean more towards the 5.13, though. just my 2 cents.

 

[rwilde03]

2020 Gladiator Rubi. I have 37" Toyo 13.5's and went with the 5.13. The stock gears would not get out of 6th with he wider and bigger tire. The 5.13 uses all the gears almost like stock and much better gas mileage. Performance Offroad is great and have almost instant power in 4H and 4L. Freeway speeds are no problem. I usually hang around 70-72 mph, but can get up in the 80's if needed. I have not tried to tow, but I do have a full size spare underneath and a rack with a roof top tent.

 

[Muddzy]

My experience with 5.13’s and 37’s has been quite the opposite. I believe it was a particular banned site the mentioned kickdown to 5th was lost. However, that is speed/RPM dependent and I have not lost that running 65-70. I suppose the RPM range might be too high for that to occur if you’re running 80, but I rarely run the rig that fast and not sure why I’d be kicking down at 80. 5.13’s have certainly made the driving experience more pleasurable. I want to eventually go 5.38’s with the 37’s.

I think I will be in the same situation as you. I have plans to overland tow 5500lbs and some of those trips will be in the Rockies. I already towed a 2500lb teardrop up some steep Colorado roads in my JKUR with 4.10s, 2.5in lift and 35s and it was a dog gasping for power on some of the steeper hills. I just got a JTR with 4.10s, 37s and 2.5in lift so I'm going to regear. I'm doing either 5.13s or 5.38s but I'm waffling on the 5.38s since I'll only be towing that much weight maybe 6x a year so the majority of the year I'll be DD or overlanding off-road from the JT without towing. Are you worried about 5.38s not working for the majority of your driving or does the benefit while towing still outweigh all else?

 

[Marine2947]

How are people’s experiences using 5.13s on the highway? Leaning towards 5.13s now that I have read this thread. My set up: JTR, 3 inch RK Pro lift, 37inch tires, automatic. Will be towing a 3k # trailer in UT, CO, NM, NV, out west.

 

[KurtP]

How are people’s experiences using 5.13s on the highway? Leaning towards 5.13s now that I have read this thread. My set up: JTR, 3 inch RK Pro lift, 37inch tires, automatic. Will be towing a 3k # trailer in UT, CO, NM, NV, out west.

Fwiw, I have 4.88’s on my 37’s, but if that was my use i would 100% go 5.13.

 

[Muddzy]

How are people’s experiences using 5.13s on the highway? Leaning towards 5.13s now that I have read this thread. My set up: JTR, 3 inch RK Pro lift, 37inch tires, automatic. Will be towing a 3k # trailer in UT, CO, NM, NV, out west.

If you read the 2 guys's posts in this thread from Colorado, they both are saying they wish they went to 5.38s instead of 5.13s, I believe.

 

[Muddzy]

I've done a lot of research on 35 and 37" tires and the need/desire to change gearing. I also talked to 2 reputable off road shops in my area. Here is my summary for those that just read the last few pages. I am not an expert so this information has been gathered from very respected, experienced people that know, install and use regeared Jeeps.

There are a lot of JK, JL, and a few JT owners that have lifts and 35s/37s that do serious off road or do heavy towing with elevation. Most of them installed 5.13s or 5.38s and some would go lower (higher gear ratio number) if they could. I've never found anyone that was unhappy with their 5.38s but there are those that did 5.13s that wished they had gone to 5.38s. With 37in tires the 5.38s work great for those hard uses AND there is NO documented proof that the smaller pinion of the 5.38s reduces the experienced real world durability. The proper installation is also important since a failure due to an improper gearing installation might be blamed on the smaller pinion. Also, when doing hard wheeling or towing, there are other components in the drivetrain that are the weak link before the pinion. On auto motors with 37s / 5.38s the rpms work well at all posted highway speeds due to the 8 spd auto. Gas mileage will vary...at upper end, highway speeds it will drop but the engine won't lug as much in some scenarios and that offsets an undetermined amount of the dropped MPG. There are too many variables to know the exact impact on MPG and I haven't found anyone that did a controlled before /after comparison.

Bottom line on heavy towing and/or serious off road with an auto JT that has 37s. Get the 5.38s properly installed and you will be happy! If you are NOT going to do heavy towing or serious off-road and don't live at higher elevation/climb hills, then the factory 4.10s are fine to some. I will be going to 5.38s sometime this year doing serious towing on and off road. I will be pushing my JT to it's limits and I will report back.

 

[FLUndertaker]

I've done a lot of research on 35 and 37" tires and the need/desire to change gearing. I also talked to 2 reputable off road shops in my area. Here is my summary for those that just read the last few pages. I am not an expert so this information has been gathered from very respected, experienced people that know, install and use regeared Jeeps.

There are a lot of JK, JL, and a few JT owners that have lifts and 35s/37s that do serious off road or do heavy towing with elevation. Most of them installed 5.13s or 5.38s and some would go lower (higher gear ratio number) if they could. I've never found anyone that was unhappy with their 5.38s but there are those that did 5.13s that wished they had gone to 5.38s. With 37in tires the 5.38s work great for those hard uses AND there is NO documented proof that the smaller pinion of the 5.38s reduces the experienced real world durability. The proper installation is also important since a failure due to an improper gearing installation might be blamed on the smaller pinion. Also, when doing hard wheeling or towing, there are other components in the drivetrain that are the weak link before the pinion. On auto motors with 37s / 5.38s the rpms work well at all posted highway speeds due to the 8 spd auto. Gas mileage will vary...at upper end, highway speeds it will drop but the engine won't lug as much in some scenarios and that offsets an undetermined amount of the dropped MPG. There are too many variables to know the exact impact on MPG and I haven't found anyone that did a controlled before /after comparison.

Bottom line on heavy towing and/or serious off road with an auto JT that has 37s. Get the 5.38s properly installed and you will be happy! If you are NOT going to do heavy towing or serious off-road and don't live at higher elevation/climb hills, then the factory 4.10s are fine to some. I will be going to 5.38s sometime this year doing serious towing on and off road. I will be pushing my JT to it's limits and I will report back.

4.10 with 37” aren’t fine anywhere. I have this currently at 1200’ elevation and it’s sucks. 8th gear is a unicorn. Anyone who has this set up and is fine with it is in denial. Yeah you can live with it and I understand not everyone can drop $1500+ on a regear so yes people do it all the time. Tolerating it and saying it’s fine are 2 different things.
I’m going with 5.13 for the reasons you mentioned.
My local 4WP yesterday tried to talk me out of 5.13 and said 4.88 is the deepest they recommend on any D44. Ignorance abounds.

 

[Muddzy]

4.10 with 37” aren’t fine anywhere. I have this currently at 1200’ elevation and it’s sucks. 8th gear is a unicorn. Anyone who has this set up and is fine with it is in denial. Yeah you can live with it and I understand not everyone can drop $1500+ on a regear so yes people do it all the time. Tolerating it and saying it’s fine are 2 different things.
I’m going with 5.13 for the reasons you mentioned.
My local 4WP yesterday tried to talk me out of 5.13 and said 4.88 is the deepest they recommend on any D44. Ignorance abounds.

Regarding 4.10s...I get what you're saying. But there are those that are really adamant about it being more than just OK so I provided that info. I currently have 4.10s on 37s, although I also have a pedal commander throttle controller which def helps. I haven't towed or wheeled with it yet but I would characterize driving locally and on highways in my setup as fine. If I was a mall cruiser with the occasional 2-4hr highway trip I honestly don't know if I would spend the $ on a regear with a pedal commander installed (I haven't ever driven the JT without it).

In the end, as long as the owner is happy that's all that matters. FYI...in my area I got 4 quotes to regear and none are from a dealer. Two at $2k and the others were $2450 and $3k. The most reputable shop is the $3k. Crazy pricing.

 

[NCLife]

Anyone in the Charlotte NC area have a shop they would recommend to get the re-gearing done?

 

[Mr. Wuf]

Anyone in the Charlotte NC area have a shop they would recommend to get the re-gearing done?

Rubitrux is in Boone. They have a great reputation, and if they weren’t five hours away from me, they’d have done my gears.

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