Sponsored

Gears for 37" tires

AV8tor

Well-Known Member
First Name
Matt
Joined
Jan 17, 2020
Threads
17
Messages
65
Reaction score
13
Location
NorCal
Vehicle(s)
73 Ford Bronco, Gladiator soon!
I’m on the 4.88 vs 5.13 debate myself. I’ve got the auto w/ 37s and 4.11s and I’m getting 17-18mpg on my weekly route of daily driving. The plan is to get a trailer in the 3K# weight range and start doing some exploring. Leaning towards 5.13s but hoping that the extra RPMs won’t hurt my MPGs to bad on the highway driving when I’m commuting and not towing.
Sponsored

 

Muddzy

Well-Known Member
First Name
Keith
Joined
Feb 19, 2021
Threads
0
Messages
65
Reaction score
62
Location
NJ
Vehicle(s)
2020 JTR, 2013 JKUR, 2008 JKU Sahara (sold)
I’m on the 4.88 vs 5.13 debate myself. I’ve got the auto w/ 37s and 4.11s and I’m getting 17-18mpg on my weekly route of daily driving. The plan is to get a trailer in the 3K# weight range and start doing some exploring. Leaning towards 5.13s but hoping that the extra RPMs won’t hurt my MPGs to bad on the highway driving when I’m commuting and not towing.
Not sure if you've read my summary (& others can answer with direct experience) but everything I've read and the shops I've talked to (and it was a lot)- they all say go lower if you're frequently towing significant weight up inclines, off-road and/or at elevation. Highway performance is going to suffer a little but that is offset some by the motor not lugging. Too many variables to accurately state what actual fuel economy on 4.10 vs deeper gears but you could do real world numbers now both highway and towing (trying to keep same payload) and then compare to when you regear. I'm going to 5.38s and I will be doing substantial highway driving (but not daily).
 

KurtP

Well-Known Member
First Name
Kurt
Joined
Oct 9, 2020
Threads
68
Messages
2,310
Reaction score
2,992
Location
VA
Vehicle(s)
S/C Mojave
Occupation
Only Fans Content Creator
Anyone in the Charlotte NC area have a shop they would recommend to get the re-gearing done?
Look up ChevyMitchell over on the JL side. Good dude. He is in NC
 

Russler

Well-Known Member
First Name
Rusty
Joined
Oct 14, 2019
Threads
13
Messages
355
Reaction score
529
Location
Heath TX
Vehicle(s)
Previous 50 Willys, 76 CJ
Build Thread
Link
No experience with 5:13's but went 4:88's in my manual (6 spd) Rubi for two reasons. 1- I bought the Mopar Performance Parts 4:88's and had the dealership install them so they couldn't bust my balls if/when I needed any warranty work. 2- When I put a level and tape on my Nitto Ridge Grappler 37's they are actually 36" tall (running 30 psi front/29.5" rear after chalk test). When I did the calculation using 36" vs the 37" I felt the 5:13's may be a little to low for the highway driving I do.

I am very happy with the 4:88's. It is great to have 1st and reverse back + I can use and stay in 6th gear even on rolling hill w/ a headwind.

Good luck to everyone trying to make this decision....it took my 5k miles to finally pull the trigger. Wish I would have done it day 1.
 

Sponsored

Muddzy

Well-Known Member
First Name
Keith
Joined
Feb 19, 2021
Threads
0
Messages
65
Reaction score
62
Location
NJ
Vehicle(s)
2020 JTR, 2013 JKUR, 2008 JKU Sahara (sold)
Good luck to everyone trying to make this decision....it took my 5k miles to finally pull the trigger. Wish I would have done it day 1.
If I correctly remember all of the posts I've read from the dozens of different posters that have lowered their gears in different jeep forums - the majority say the same thing about wishing they had done it from day 1. I don't believe I've read anywhere that people feel they overshot by going too low and wish they had chose a little higher. People are either really happy with their chosen lower gearing or they wish they went even lower.
 

mellendic

Well-Known Member
First Name
Rick
Joined
Jan 14, 2021
Threads
3
Messages
178
Reaction score
300
Location
Maryland
Website
revkit.com
Vehicle(s)
2021 Jeep Gladiator Mojave
Occupation
IT Security Researcher
I just got mine back with 5.13s, I have a Mojave with a 3.5 inch metal cloak game changer lift and 37x13.5 toyo open country MTs. They measure out at 30psi to 36.2. Before the gears (about 1000 miles on the lift) it was dragging and not shifting properly at all with reprogramming. I am 90 moles into the 5.13s and there is a major and noticeable difference. I am going to verify mileage soon. I was 13-14 mpg after the lift. 16-17 stock. Once I am through the break in I will repost new mileage.
 

hjdca

Well-Known Member
Joined
Oct 27, 2019
Threads
9
Messages
1,639
Reaction score
2,324
Location
Southern California Mountains
Vehicle(s)
Jeep Gladiator Rubicon manual Sting Gray
Build Thread
Link
I just got mine back with 5.13s, I have a Mojave with a 3.5 inch metal cloak game changer lift and 37x13.5 toyo open country MTs. They measure out at 30psi to 36.2. Before the gears (about 1000 miles on the lift) it was dragging and not shifting properly at all with reprogramming. I am 90 moles into the 5.13s and there is a major and noticeable difference. I am going to verify mileage soon. I was 13-14 mpg after the lift. 16-17 stock. Once I am through the break in I will repost new mileage.
Congrats ! For mileage calculations, make sure you check your mph with GPS. Even if you think you put in the right numbers, it will probably be 1 or 2 mph off. Do not be afraid to increase the tire size from what you measured to get the right mph at 70 mph. It's best to use the cruise control to get the most accurate numbers.
 

mellendic

Well-Known Member
First Name
Rick
Joined
Jan 14, 2021
Threads
3
Messages
178
Reaction score
300
Location
Maryland
Website
revkit.com
Vehicle(s)
2021 Jeep Gladiator Mojave
Occupation
IT Security Researcher
Congrats ! For mileage calculations, make sure you check your mph with GPS. Even if you think you put in the right numbers, it will probably be 1 or 2 mph off. Do not be afraid to increase the tire size from what you measured to get the right mph at 70 mph. It's best to use the cruise control to get the most accurate numbers.
Happily I have already checked with 2 different GPS units both with 13 birds... very accurate, both US based and GLONAS
 

mellendic

Well-Known Member
First Name
Rick
Joined
Jan 14, 2021
Threads
3
Messages
178
Reaction score
300
Location
Maryland
Website
revkit.com
Vehicle(s)
2021 Jeep Gladiator Mojave
Occupation
IT Security Researcher
OK 300 miles on the gears, and they have been tempered... getting the diff fluid changed in a few days at 500 miles. AMAZING results so far. was at 11.7 MPG, now 16.4, shifting is correct as it used to be, and RPMs are down! this is the best change I have made yet.

IMG_0439.JPEG
 

Sponsored

EstoJTR

Well-Known Member
First Name
Erx
Joined
Jun 29, 2020
Threads
4
Messages
199
Reaction score
220
Location
Colorado
Vehicle(s)
2020 Sting Gray JTR, 2014 Cayman S, 2020 RDX Advance
Question for the gearing group. If one has plans to do a supercharger at a later date, is it wiser to wait and do that first and then re-gear, to re-gear first then blower, or it doesn't really matter? I'm also at elevation out in CO.
 

Muddzy

Well-Known Member
First Name
Keith
Joined
Feb 19, 2021
Threads
0
Messages
65
Reaction score
62
Location
NJ
Vehicle(s)
2020 JTR, 2013 JKUR, 2008 JKU Sahara (sold)
OK 300 miles on the gears, and they have been tempered... getting the diff fluid changed in a few days at 500 miles. AMAZING results so far. was at 11.7 MPG, now 16.4, shifting is correct as it used to be, and RPMs are down! this is the best change I have made yet.

Jeep Gladiator Gears for 37" tires IMG_0439.JPEG
That's awesome results! Plz remind us what your setup is and the gears you chose?
 

kelkolb

Well-Known Member
First Name
Kelley
Joined
Aug 21, 2019
Threads
12
Messages
400
Reaction score
300
Location
Greensboro, NC
Vehicle(s)
2020 Gladiator Sport S
Occupation
Mechanical Engineer
Question for the gearing group. If one has plans to do a supercharger at a later date, is it wiser to wait and do that first and then re-gear, to re-gear first then blower, or it doesn't really matter? I'm also at elevation out in CO.
I'd just go with the equivalent gearing to factory (4.56 for 35's, 4.88 for 37's) given the SC will likely get your more low end power where you would normally use the gearing to get that.

EDIT: Magnuson for instance specifically says it's designed for stock so the factory gearing equivalent would definitely be the way to go. You would need a custom tune though because you'll be loading the engine differently with the added tire/wheel weights over stock. Their standard tune would be for stock only.
 

AZCooWhip

Well-Known Member
First Name
Rick
Joined
Jan 9, 2021
Threads
44
Messages
1,018
Reaction score
2,214
Location
N. Phoenix
Vehicle(s)
2021 Gladiator
OK 300 miles on the gears, and they have been tempered... getting the diff fluid changed in a few days at 500 miles. AMAZING results so far. was at 11.7 MPG, now 16.4, shifting is correct as it used to be, and RPMs are down! this is the best change I have made yet.

IMG_0439.JPEG
Same here. 4:88s with 37x13.5x17 Cooper STTs on a 3” lift. Everything else is stock.

100 miles shy of break in on Yukon gears and am getting almost 18mpg. 17.7 to be exact. That’s around town stop and go driving here in Phoenix. Very little highway driving yet.

What highway driving I have done, I hit and HOLD #8 consistently. Off light acceleration is/feels better than stock 4:10s on 33s.

Very satisfied with my choice and combo.
 

mellendic

Well-Known Member
First Name
Rick
Joined
Jan 14, 2021
Threads
3
Messages
178
Reaction score
300
Location
Maryland
Website
revkit.com
Vehicle(s)
2021 Jeep Gladiator Mojave
Occupation
IT Security Researcher
That's awesome results! Plz remind us what your setup is and the gears you chose?
3.5 inch metalcloak game changer, 37x13.5 toyo open country, steel bumpers front and rear, metal cloak diff covers, and yukon 5.13s afe intake, TBS, and shorty dump exhaust, and iDrive pedal commander, and AFE scorcher remapping for the air intake, and a procal programmer, and a bunch more stuff.
Sponsored

 
 



Top