Regear - 4.56 or 4.88 for overland JKU

harv3589

Adventurer
Just wondering what would be a better idea...4.56 or 4.88 gears for our JKU? We pull a M101 for camping and it works hard right now on any hills with 3.73 gears. It has a Dana 30 front so that may play into this decision. It’s also a daily driver for my wife so don’t want to completely kill the gas mileage but it does have 35” tires.

Anyone with experience here?
 
I have a JKUR and pull a Bantam trailer. I run 35s, and had 4.10 stock. But, I also have a D44 front. The 4.10 gears did alright, until I came to a mountain pass. Then the transmission would shift into 3rd or even 2nd. The engine would spin at higher rpms then I liked. I went with 4.88 and love them. My mileage did decline some. Having said that, with a D30 front, I wouldn’t go any lower than 4.56. The pinion shaft gets awfully stressed on a 30 front if you go to deep.
 

FosterWV

Baller On A Budget
There's not much difference between 4.56/4.88

JKs run a HP30 so 4.88 will be fine.....plus you don't tow or highway drive in 4WD so no worries about the front axle strength.

For MPGs google a gear tire chart and compare your current rpm to gear options
 

rho

Lost again
Year also matters. I re-geared my '12 from 3.21 to 4.56 and it was a night and day difference. I have a manual transmission though and I'm currently running 285/75/16 tires on it. The gearing is a bit deep for that tire size but I expect it to be just right when I go up to 35" or 315/75/17 tires. I don't tow with mine so I can't offer input on that.

As for around town... well, its a lifted jeep, its not going to be good no matter what, I think if your jeep is ok pulling the trailer now with your stock gearing, 4.56 might be ok?
 

harv3589

Adventurer
It works hard towing and lots of times runs in 4th or sometimes 3rd gear on hwy so a regear would be a huge benefit. I’m tempted to do the 4.88 but worried about the rest of time when we aren’t pulling the trailer. Is it worth it or should I settle on the 4.56.
 

bobholthaus

Observer
Would 4.10s even be an option? I have the same setup and pull about the same trailer so I appreciate the comments here.


Sent from my iPad using Tapatalk Pro
 

Happy Joe

Apprentice Geezer
I'm guessing automatic transmission;
The difference between 4.88 and 4.56 is less than 10%; if no towing I would say 4.56..

The M-101 is rated at 3/4 ton so I would go with the 4.88s, perhaps even more depending on the torque & horsepower of your engine. I would also highly recommend additional transmission cooling...

Enjoy!
 
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SoDakSooner

Adventurer
Exact same setup as you. I went with 4.56's, but in retrospect I should have done 4.88's. The 4.56's are fine but a little more grunt wouldn't hurt.
trailer21.jpg
 

TxhardrockJK

New member
I think it’s such a small difference either would be good, but towing, I would say even a little more is better, like stated above by SoDakSooner. I just went to 4.88s, I have a ‘16 Rubicon Auto with 35” ko2s I’m at 3000 RPMs at 78mph, but I don’t tow anymore.
 

St8ton

Member
4.56 is my recommendation. 35's with that ratio will turn close to 2700-2800 RPMs at 70mph. Any more and you are starting to get a little high in the Revs.
My .02
 

DallasJKU

Adventurer
I've been thinking about re-gearing. I have 4.10's on my Recon with 315 KO2's. Not sure 4.56 is worth the upgrade, but I'm afraid 4.88's would be too low especially since I never tow.
 
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