Golvach

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Several people asked me to post my experience with 4.56 gears, so here it is. I've got a 2021 Gladiator Overland, 3.6L V6 with manual transmission, which came with the 3.73 gears. A couple of months ago I added a Mopar 2" lift and 35 inch mud terrain tires. Last week, I had the gears swapped to 4.56. My goal for my build was to get a perfect blend between (1) a pretty darn nice daily driver truck (I came from a F150) and (2) a respectably offroad capable real Jeep. I think I have now achieved exactly that and I absolutely love the way it turned out:

Why I regeared: As soon as I added the lift and bigger tires, while still running the 3.73 gears, my truck felt severely under-powered. My gas mileage dropped from 17 mpg city/20 mpg highway to about 12 mpg no matter where I was driving. First gear starts became WAY more prone to stalling and felt very sluggish. On the highway, 5th and 6th gear became nearly useless--no power, no ability to maintain speed or pass in 5th or 6th, and constant downshifting. At 70 mph I was hitting about 2,000 rpm in 6th gear. If I hit even the slightest incline or wind, I could have the throttle completely opened up and would still be losing speed. I drive across Texas a lot, and through the Hill Country here in particular, so this was just intolerable for me.

Why I chose 4.56: I first thought about 4.10s. I talked to several "jeep people" online and in person, and everyone said regearing to 4.10 would be a waste of time and that I should be considering 4.56 or 4.88. So then I went back and forth between 4.56 and 4.88 a lot--reading forums about different experiences with each (mainly on the JL platform though--not as much info out there on the manual trans JTs), etc. I even changed my regear order back and forth a couple of times.

My main focus was increasing the RPMs in top gear back into the natural power band of the 3.6L V6 and restoring the fuel efficiency, but I also wanted a little more offroad performance vs my stock setup. The offroad shop that did the work estimated that with 4.56 gears in 6th gear at 75 mph, I would hit 2400-2500 RPM, and that would increase to 2600-2700 RPMs with 4.88s. The 4.88 option sounded like I would be running the engine a little harder than I wanted, but really would have been fine for the vehicle, and it would definitely have a lot of power. But first gear also would probably be really short with the 4.88s, and a lot of JL folks said their rides just felt a little too "tall" with the 4.88s and 35s.

Ultimately I went with the 4.56, which I determined would be just slightly over-geared compared to a stock Rubicon or Max Tow Sport (both have 4.10s) and would get the RPMs in a really good sweet spot on the highway... which sounded like exactly what I was going for.

After the regear: I just finished my 500-mile, grandma-driving break-in period on the new gears and had the gear oil drained and refilled. Now that I can drive normally again, my gas mileage has improved noticeably--roughly 17-18 mpg in the city and I've gotten similar results on short highway drives. Additionally, throughout 1st-6th gear there is significantly more power. My truck is noticeably peppier than stock off the line, and starts are much easier... let out the clutch and the truck does most of the work. 1st is quick and full of torque, but not so much that it feels like I'm driving a tractor... feels more like the power you'd get in a V8 full-size truck off the line. 5th and 6th gear maintain speed on the highway with absolutely no problem, even in hills and wind.. with no downshifting needed so far. I can accelerate to pass in 6th (which I could barely do even before the lift & tires). I'm at exactly 2,500 rpms at 75mph which feels perfect on this engine. It will be so nice to have functional cruise control in this thing now!

I'm taking it to Moab pretty soon and will report back on the long-drive and offroad experience, but so far the 4.56 seems to be the absolute sweet spot.... a little sportier feeling than a stock rubicon, but not so much that it feels like a weekend-only vehicle. Fuel efficiency is respectable so far, and it's very responsive and powerful through all gears. Feels to me like 4.88s would have been a little too much for what I was going for, and so far couldn't be happier with the pairing of 4.56s on 35 inch tires.

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Tufelhundin

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AWESOME!!!!! Thank you for the in-depth review. My JT is currently having 4.56's added and Im hoping to be able to pick it up tomorrow. Im guessing my break-in will be VERY quick for I'm almost 3hrs away from the shop so I'll have a chunk of miles real quick just trying to get home.

Your review certainly makes me feel better about my choice along with others that have chimed in from going from 3.73's to 4.56's.

Enjoy it brutha, for its a dang pretty ride for sure!
 

colindo

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Several people asked me to post my experience with 4.56 gears, so here it is. I've got a 2021 Gladiator Overland, 3.6L V6 with manual transmission, which came with the 3.73 gears. A couple of months ago I added a Mopar 2" lift and 35 inch mud terrain tires. Last week, I had the gears swapped to 4.56. My goal for my build was to get a perfect blend between (1) a pretty darn nice daily driver truck (I came from a F150) and (2) a respectably offroad capable real Jeep. I think I have now achieved exactly that and I absolutely love the way it turned out:

Why I regeared: As soon as I added the lift and bigger tires, while still running the 3.73 gears, my truck felt severely under-powered. My gas mileage dropped from 17 mpg city/20 mpg highway to about 12 mpg no matter where I was driving. First gear starts became WAY more prone to stalling and felt very sluggish. On the highway, 5th and 6th gear became nearly useless--no power, no ability to maintain speed or pass in 5th or 6th, and constant downshifting. At 70 mph I was hitting about 2,000 rpm in 6th gear. If I hit even the slightest incline or wind, I could have the throttle completely opened up and would still be losing speed. I drive across Texas a lot, and through the Hill Country here in particular, so this was just intolerable for me.

Why I chose 4.56: I first thought about 4.10s. I talked to several "jeep people" online and in person, and everyone said regearing to 4.10 would be a waste of time and that I should be considering 4.56 or 4.88. So then I went back and forth between 4.56 and 4.88 a lot--reading forums about different experiences with each (mainly on the JL platform though--not as much info out there on the manual trans JTs), etc. I even changed my regear order back and forth a couple of times.

My main focus was increasing the RPMs in top gear back into the natural power band of the 3.6L V6 and restoring the fuel efficiency, but I also wanted a little more offroad performance vs my stock setup. The offroad shop that did the work estimated that with 4.56 gears in 6th gear at 75 mph, I would hit 2400-2500 RPM, and that would increase to 2600-2700 RPMs with 4.88s. The 4.88 option sounded like I would be running the engine a little harder than I wanted, but really would have been fine for the vehicle, and it would definitely have a lot of power. But first gear also would probably be really short with the 4.88s, and a lot of JL folks said their rides just felt a little too "tall" with the 4.88s and 35s.

Ultimately I went with the 4.56, which I determined would be just slightly over-geared compared to a stock Rubicon or Max Tow Sport (both have 4.10s) and would get the RPMs in a really good sweet spot on the highway... which sounded like exactly what I was going for.

After the regear: I just finished my 500-mile, grandma-driving break-in period on the new gears and had the gear oil drained and refilled. Now that I can drive normally again, my gas mileage has improved noticeably--roughly 17-18 mpg in the city and I've gotten similar results on short highway drives. Additionally, throughout 1st-6th gear there is significantly more power. My truck is noticeably peppier than stock off the line, and starts are much easier... let out the clutch and the truck does most of the work. 1st is quick and full of torque, but not so much that it feels like I'm driving a tractor... feels more like the power you'd get in a V8 full-size truck off the line. 5th and 6th gear maintain speed on the highway with absolutely no problem, even in hills and wind.. with no downshifting needed so far. I can accelerate to pass in 6th (which I could barely do even before the lift & tires). I'm at exactly 2,500 rpms at 75mph which feels perfect on this engine. It will be so nice to have functional cruise control in this thing now!

I'm taking it to Moab pretty soon and will report back on the long-drive and offroad experience, but so far the 4.56 seems to be the absolute sweet spot.... a little sportier feeling than a stock rubicon, but not so much that it feels like a weekend-only vehicle. Fuel efficiency is respectable so far, and it's very responsive and powerful through all gears. Feels to me like 4.88s would have been a little too much for what I was going for, and so far couldn't be happier with the pairing of 4.56s on 35 inch tires.

IMG_4286.JPG
IMG_4314.JPG
I appreciate the write up as I have had the same back and forth. I have a 2020 Granite Crystal Overland but with the auto tranny. I went with a COR 2.5" Overland+ lift and 35's and have noticed the same sluggish feeling you did. I haven't noticed that significant of a drop off in mileage but I do mostly highway driving. I plan on regearing as soon as I have the funds to do so.
 

93civej1

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thanks for the write up. Great looking truck.
 

HjStrater

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AWESOME!!!!! Thank you for the in-depth review. My JT is currently having 4.56's added and Im hoping to be able to pick it up tomorrow. Im guessing my break-in will be VERY quick for I'm almost 3hrs away from the shop so I'll have a chunk of miles real quick just trying to get home.

Your review certainly makes me feel better about my choice along with others that have chimed in from going from 3.73's to 4.56's.

Enjoy it brutha, for its a dang pretty ride for sure!
Curious on your gas mileage if you have an auto. I run 35's on 3.73 gears and get 16-17 still but would love a bit more power.
 

Tufelhundin

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Curious on your gas mileage if you have an auto. I run 35's on 3.73 gears and get 16-17 still but would love a bit more power.
I get about 15-16 with 3.73’s

I have photo in the log thread where I did a 2k mile trip and it was just under 16.
Having said that, mile mileage has always sucked. My brother has the exact jt I have but his is silver and he was getting 21-22 when stock... I got 19 once... and after that it was around 17 or so. Small note... when I went to Dallas to get a set of rubi wheels and tires I found my mph was off with the gps and was dead on with the rubi’s... so maybe that had something to do with it.

I just put 4.56 in mine and picked it up yesterday, had a 130 mile drive to get home... it gets to 8th VERY easily and rather quick. Mpgs may be up a lil as long as I keep it under 65-70 of course.

I have two pics here somewhere that I took with cruise on in stock gearing and 35’s. It was in 7th and at 17 or 18 mpg at 60. A minute later I took another pic with cruise set at 65mph... 15mpg and it would not leave 6th.
 

Chaosmtb

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I get about 15-16 with 3.73’s

I have photo in the log thread where I did a 2k mile trip and it was just under 16.
Having said that, mile mileage has always sucked. My brother has the exact jt I have but his is silver and he was getting 21-22 when stock... I got 19 once... and after that it was around 17 or so. Small note... when I went to Dallas to get a set of rubi wheels and tires I found my mph was off with the gps and was dead on with the rubi’s... so maybe that had something to do with it.

I just put 4.56 in mine and picked it up yesterday, had a 130 mile drive to get home... it gets to 8th VERY easily and rather quick. Mpgs may be up a lil as long as I keep it under 65-70 of course.

I have two pics here somewhere that I took with cruise on in stock gearing and 35’s. It was in 7th and at 17 or 18 mpg at 60. A minute later I took another pic with cruise set at 65mph... 15mpg and it would not leave 6th.
I’m on the fence about 4.56-4.88 seems like I can’t go wrong with either, but maybe post your rpms at 70 in 8th, I know there’s “calculations” but real world is always mixed. Thanks!
 

Nitroexpress

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Excellent write up. I think you might have mis-posted in the wrong section? You are in the Classified ad section. I'm not trying to be the forum police, just wanted your effort to be available to those looking for this valuable information.
 

Gren71

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I have 4.10s in auto and have been thinking about maybe doing this at some point. 4.56 seems to be the right size for folks who want more performance with a daily driver and light beach movement/towing.

my only question is...and I'm sure its a newb question...did y'all only do the rear? or both front and rear?
 

Tufelhundin

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@Chaosmtb

looks like about 2100 at 70. The closest I could get tire size/mph using 2 speed apps and Waze was about 1 mph less than indicated. So I was roughly going 69mph via GPS.

I know one thing, with the 4.56 it should be call a Max Sport, lol.

Edit: I just looked at Grimmjeeper and at 70mph it shows 2091 rpm.

DC3935DA-DB9A-4E95-9887-85584C7579BC.jpeg
 

OMTBiker

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I have 4.10s in auto and have been thinking about maybe doing this at some point. 4.56 seems to be the right size for folks who want more performance with a daily driver and light beach movement/towing.

my only question is...and I'm sure its a newb question...did y'all only do the rear? or both front and rear?
You have to have matching gear ratios front and back, you re-gear both axles.
 

Chaosmtb

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@Tufelhundin

Nice! Definitely the best setup for 35’s. I think the 8spd has a different philosophy on it than the earlier generations. Being a double overdrive. 8 gear needs to be just a fuel saver. The tranny has such a wide range of gears that it will not lack much power if you push it, sure with gears you get a better grunt off the line, but for a jeep that sees a lot of highway the auto has plenty of range to deliver power at fuel gobbling rpms, but when your cruising I think it’s best to aim for 8 with eco in mind. Not sitting in a 2500 rpm power band like the 5 speeds, I like to push my jeep hard and 4.56 will have an extra pinion tooth, Also less leverage on the axles, little less torque, but not undergeared. If I was towing an adventure trailer or going 37 deff 4.88 but I really trying to keep my jlur mild on 35’s I rather break traction than parts! Skid plates and a winch will get me up anything!
 

j.o.y.ride

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@Chaosmtb

looks like about 2100 at 70. The closest I could get tire size/mph using 2 speed apps and Waze was about 1 mph less than indicated. So I was roughly going 69mph via GPS.

I know one thing, with the 4.56 it should be call a Max Sport, lol.

Edit: I just looked at Grimmjeeper and at 70mph it shows 2091 rpm.

DC3935DA-DB9A-4E95-9887-85584C7579BC.jpeg
Can you confirm this is 8th gear and not 7th?
 

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