Need help about regearing

Osalamah

Osalamah

New member
Hey if anyone can help me out on this I'd really appreciate it. I have a 2016 jeep wrangler unlimited sport and I just put on some 37 inch tires with a 3.5 inch lift kit, now I keep hearing from my buddies about re gearing and what not. I don't know much about it but this video did help but with people with experience what's the best re gearing numbers should I start looking at getting I never go off road, I daily drive my jeep. Hardly go on the highway just city and suburban driving. If anyone can help I'll appreciate it thank you.


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Osalamah said:
Hey if anyone can help me out on this I'd really appreciate it. I have a 2016 jeep wrangler unlimited sport and I just put on some 37 inch tires with a 3.5 inch lift kit, now I keep hearing from my buddies about re gearing and what not. I don't know much about it but this video did help but with people with experience what's the best re gearing numbers should I start looking at getting I never go off road, I daily drive my jeep. Hardly go on the highway just city and suburban driving. If anyone can help I'll appreciate it thank you.


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Buy a Prius. They're geared perfectly for city driving. 😎

4.88s would probably be fine for you.

--
Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407
 
Osalamah said:
Hey if anyone can help me out on this I'd really appreciate it. I have a 2016 jeep wrangler unlimited sport and I just put on some 37 inch tires with a 3.5 inch lift kit, now I keep hearing from my buddies about re gearing and what not. I don't know much about it but this video did help but with people with experience what's the best re gearing numbers should I start looking at getting I never go off road, I daily drive my jeep. Hardly go on the highway just city and suburban driving. If anyone can help I'll appreciate it thank you.


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Welcome! Check this out.
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Seahawkfan said:
Welcome! Check this out.
View attachment 319972
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Ya I showed one of my buddies that and I have a 3.6 automatic, he still told me to go with the 4.88 but in the pic it says for a good daily driver 4.56 so now that I'm somewhat confused but then again I have very little knowledge and I'd admit to that no shame, we all start somewhere. So I don't know what the whole re gearing does, or even if I need it or not that's why I'm here for some help so I'll take any advice if it's recommended for me if I don't go off road at all
 
Osalamah said:
Ya I showed one of my buddies that and I have a 3.6 automatic, he still told me to go with the 4.88 but in the pic it says for a good daily driver 4.56 so now that I'm somewhat confused but then again I have very little knowledge and I'd admit to that no shame, we all start somewhere. So I don't know what the whole re gearing does, or even if I need it or not that's why I'm here for some help so I'll take any advice if it's recommended for me if I don't go off road at all
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I think that to best understand re-gearing and why, think of a mountain bike. The tire size can be associated to a hill for a biker. So with that knowledge, if you have big hill to climb what do you do? You have to choose the small sprocket in the front (bicycle) and the largest in the back. You will pedal a lot faster to go the same speed, but your effort will be minimal. Reverse this concept, big up front and small out back, and you will find that it is very hard to make a revolution but you will go much faster.
Now for the Jeep it is the same idea. Larger tire will require taller gears (higher numbers). There is a sweet spot that will help with RPMs and speed relation. With 37” tires you would want to help your car with gearing to 4:56 if you reside in flat areas. Or 4:88 if you have a few hills around you. Important (but obvious to all people involved) the gear ratios has to match front and rear.

I hope I did not confuse you even more. Just trying to help.



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mallavoider said:
I think that to best understand re-gearing and why, think of a mountain bike. The tire size can be associated to a hill for a biker. So with that knowledge, if you have big hill to climb what do you do? You have to choose the small sprocket in the front (bicycle) and the largest in the back. You will pedal a lot faster to go the same speed, but your effort will be minimal. Reverse this concept, big up front and small out back, and you will find that it is very hard to make a revolution but you will go much faster.
Now for the Jeep it is the same idea. Larger tire will require taller gears (higher numbers). There is a sweet spot that will help with RPMs and speed relation. With 37” tires you would want to help your car with gearing to 4:56 if you reside in flat areas. Or 4:88 if you have a few hills around you. Important (but obvious to all people involved) the gear ratios has to match front and rear.

I hope I did not confuse you even more. Just trying to help.



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Okay so with re gearing it will it help me out with the whole MPG and to stay on the safe side with your example should I just stick with getting the 4.88 then?
 
I'm not by any means a pro but I read it as saying with the 4.88 you'll get a little better performance than 4.56. It will run a little bit more RPM's but not much. I run 5.13 on a 2011 JKU 3.8 on 35's now. I think I run 2700 or 2800 rpms @70 mph Jumping to 37" soon so hoping that will drop some. I think most would recommend 4.88.
 
Do not go less than 4:88s with 37s. You are in Illinois, so that should be fine. If you are in mountain type terrain regularly, I would recommend 5:13 or your Jeep will be searching for gears a lot as you climb hills on the highway.


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wjtstudios said:
Do not go less than 4:88s with 37s. You are in Illinois, so that should be fine. If you are in mountain type terrain regularly, I would recommend 5:13 or your Jeep will be searching for gears a lot as you climb hills on the highway.


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I agree with this. I went with 5.13. Now that I have them, I would have been unhappy with 4.88. I live on a mountain though and I have XD60s and all the extra weight......plus it was a good option in case I ever get around to the LS plus 40s, then the 5.13 is the obvious better choice. My RPM's now are not that much higher and I still get around 15 MPG. Hope that helps.
 
The gearing compensates for the larger diameter of the tires. Going from 3.21 to 4.88 will be a huge change in power, mpg, and how the jeep drives. First gear will feel a full gear lower and the overdrive will be useable on the highway. I'm sure your installer will know, but you'll need a new front diff carrier (they're cheap) and reprogram the computer so the speedo works right and trans shifts properly along with the gears and rebuild kits (bearings, seals, shims). You'll see about 2800rpm at 70mph, but don't worry, the 3.6 loves higher rpms.
 
I have 37s, 3.6, and auto and I feel like my 4.88s are kinda on the high side. If I didn’t row a camper throughout the summer I feel like I’d rather have 4.56s imo. I’m sitting at 3k at like 65mph on the highway and it kills my highway mpg
 
Braxtonsag said:
I have 37s, 3.6, and auto and I feel like my 4.88s are kinda on the high side. If I didn’t row a camper throughout the summer I feel like I’d rather have 4.56s imo. I’m sitting at 3k at like 65mph on the highway and it kills my highway mpg
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I know it will very slightly by tire diameter, but I have the same setup and cruise at 75 mph and at 2900 rpm. Don’t know why you are running so high???


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Braxtonsag said:
Not sure tbh, my tires have some mileage on them and measure out to about 35.5 but he’ll most 37s are only 36.5.
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Very true. I’m running 37 BFG KM2s which run notoriously small and I’m still not running as high of an RPM as you. At 65, I’m running around 2400 RPM and getting around 14 mpg depending on which way the wind blows.


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The only way I’m touching 14mpg is either downhill or going like 40-50 on a highway. I’m not sure why I get such bad gas mileage.
 
Braxtonsag said:
The only way I’m touching 14mpg is either downhill or going like 40-50 on a highway. I’m not sure why I get such bad gas mileage.
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Have you recalibrated you system with a Procal or Traildash to the proper tire size?

Gassed up and typical day load with me in the driver’s seat, the Jeep weights in at 6100 Lbs, So it’s not light. Something seems off, are you sure you have 4:88s?


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wjtstudios said:
Have you recalibrated you system with a Procal or Traildash to the proper tire size?

Gassed up and typical day load with me in the driver’s seat, the Jeep weights in at 6100 Lbs, So it’s not light. Something seems off, are you sure you have 4:88s?


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Yeah it’s got a flashcal w tire size set to 35.5, 4.88s, and Iv confirmed speedometer is correct via gps. Not sure on the weight of mine but I have aluminum fenders, soft top, completely line x’d tub, and no spare so I don’t imagine it’s extremely heavy. Need to get it down to the grainery and put it on their scale
 
Braxtonsag said:
Yeah it’s got a flashcal w tire size set to 35.5, 4.88s, and Iv confirmed speedometer is correct via gps. Not sure on the weight of mine but I have aluminum fenders, soft top, completely line x’d tub, and no spare so I don’t imagine it’s extremely heavy. Need to get it down to the grainery and put it on their scale
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It’s just weird the difference between the two jeeps. It’s got me stumped why your running that high.


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