4.88's installed, 6-spd Sport S, 37's - Finally

Fawkes

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Finally, Yukon Gears, got it back yesterday, have been working through break in now but can say it's worth it.

I can no throttle clutch crawl through drive thru now lol

Here's actual rpm data in both km/h and mph for Jeepers on both sides of the border.

*Sport S, 6-speed, 4.88, Mopar lift, 37x12.50 Falken MT's. GPS matched km/h, Tazer tire height 36.45", July 3, 2020.
Gearspeedrpmspeedrpmspeedrpm
4th110310012034501303700
5th110250012028001303000
6th110225012025001302700

*Sport S, 6-speed, 4.88, Mopar lift, 37x12.50 Falken MT's. GPS matched mph, Tazer tire height 36.45", July 3, 2020.
Gearspeedrpmspeedrpmspeedrpm
4th683100753450813700
5th682500752800813000
6th682250752500812700

My goal was 24-2500 rpm in 6th at 120 km/h (75 mph) and it does 2500 now. Goal achieved. I was driving essentially a 4-speed manual with the 3.73's and it was only happy on the street. Now i have fully useable 6-speed with no extra fluff at the top end, i don't want to do more than 75 mph in this thing.

3500 RPM Shifts
1st into 2nd = 25 km/h (16 mph)
2nd into 3rd = 47 km/h (29 mph)
3rd into 4th = 82 km/h (51 mph)

Note: with 3.73's and 35's...this 4.88's and 37's is now exactly 500 rpm higher for the same speeds.

Lastly, my Captain America dash light is coming on and saying the start/stop system needs service, even though i changed the tazer setting to 4.88's when i left the shop. Comes on after each start and get to about 40 km/h. Will have to dig into this, surely it's a simple fix. I have it disabled in the tazer settings so unsure whats up.
I changed my tires and height with a programming tool. Next day the same light came on. Dealer flashed it and It fixed. Im sure I did it correctly with Jscan but oh well. Fixed now.

 

Bbannongmu

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I did the Tazer 6th gear relearn procedure to adjust for 37s and no issues.

F9921942-AAD8-44C2-8515-968B701855D0.jpeg


92E689B7-5079-4E45-902E-807E79D0A463.jpeg
 

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ya that's what happened to mine, dealership had to do it, 4wp didn't know what to do with that for me

as for an update, i've been running these 4.88's on 37's for quite awhile and i love it, right choice, it's super fun to drive, my mileage is going down because it's too much fun to drive and i'm ripping the gears quite a bit more with the music from the magnaflow street side exit and how much zip there is, i drive more like my little redneck sportscar...so ya, i fully endorse this set up ;)
Hello Jt-wrx, I have been following your thread, and I finally ordered my Clayton 3.5" overland Plus lift, Falcon SP2 3.3 Adjustable shocks through the Black Friday savings. I plan to run the Method 313 racing wheels (light weight at 23 lbs) with Good Year MT/R Kevlars 37 inch (72 lbs). Right now, I am still debating the gears - 4:88 or 5:13 for my setup with the manual trans. I live in the mountains/hills at 2K feet. I am leaning towards 5:13 to be safe. What do you think ? Could another 200 rpm or so help with this higher lift on the fwy (ie. overcoming air resistance) ?
 
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Jt-wrx

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i live at 4000' and i feel for my lightweight truck set up that 4.88's is as far as i'd want to go, and perfect for my needs. Dad, daily, mostly empty truck, some hunting. I'm not building up an offroad or overlanding set up. So 4.88's for me is ideal plus a bit extra. I would feel over geared if my set up had 5.13's.

I'm also eyeballing good year duratrac 285-75r18's which are 35's as stud-able winter tires so 5.13's would definitely suck. At least i can drop back to 35's at any time and be same as 5.13's and 37's. I can't seem to find any skinny 37's with snowflake or stud-able. The duratrac in that size is new, some 18" wrangler/overland take off wheels and could be all set there. Those tires are light at 60 lbs too so she'd be extra quick and stout i bet.

Hope all the info helps you decide what's best for your rig.
 

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I'm mounting 37's on stock (4.10) gears soon and plan on running for a bit before I re-gear. How are you getting along?
So far, so good. Towed 3200lbs and it required a fair amount of downshifting on hills. Driving around it’s barely acceptable in hills and MPGs have gone from 16 to 13.8 or so . Off road it’s fine - Rubi 4 to 1 transfer case is unphased by the tires. Some video of on road driving and initial mpg. good luck!.
 


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So far, so good. Towed 3200lbs and it required a fair amount of downshifting on hills. Driving around it’s barely acceptable in hills and MPGs have gone from 16 to 13.8 or so . Off road it’s fine - Rubi 4 to 1 transfer case is unphased by the tires. Some video of on road driving and initial mpg. good luck!.
Thanks, it's amazing how much variance there is in everyone's experience. On 35's right now, I am averaging 17-18 with mixed driving and get closer to 20 on straight highway at 65-70 mph...I will never be the guy doing 80 in a Jeep and in my experience I have no problem in 5th or 6th at 65-70 mph in most situations...I don't climb hills in 6th, but I guarantee that the ATs aren't climbing hills in 8th either. Towing, I'm around 14-16 depending on what my load is. My tires will be mounted next Saturday, lift won't be here for a couple more weeks. Re-gear maybe in March or April unless it is just awful, but I don't think I will go 4.88...I want close to stock highway RPMs and that puts me in 4.56 from what I can see. In 6th gear at 70 mph, I'm turning 2,000 RPMs (below the power curve I know, but so far I am comfortable with what I get).
 

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Thanks, it's amazing how much variance there is in everyone's experience. On 35's right now, I am averaging 17-18 with mixed driving and get closer to 20 on straight highway at 65-70 mph...I will never be the guy doing 80 in a Jeep and in my experience I have no problem in 5th or 6th at 65-70 mph in most situations...I don't climb hills in 6th, but I guarantee that the ATs aren't climbing hills in 8th either. Towing, I'm around 14-16 depending on what my load is. My tires will be mounted next Saturday, lift won't be here for a couple more weeks. Re-gear maybe in March or April unless it is just awful, but I don't think I will go 4.88...I want close to stock highway RPMs and that puts me in 4.56 from what I can see. In 6th gear at 70 mph, I'm turning 2,000 RPMs (below the power curve I know, but so far I am comfortable with what I get).
I was not gettin my 17mpg stock. I leave my Jeep idling, drive for real short trips on back roads and gravel roads and I find my worse mileage is on the highway. I also have Ace rock rails, Ace steel bumper and Warn winch killing my mileage l. Best mileage I’ve ever gotten was no doors or top on all gravel roads for about 70 miles. Got 20mpg and average speed of 25mph. I’m thinking 4.88 or 5.13 gearing. I tow and haul and where I am is reasonably hilly. Sounds like you’ll be fine. Good luck.
 
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cgflyer

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I was not gettin my 17mpg stock. I leave my Jeep idling, drive for real short trips on back roads and gravel roads and I find my worse mileage is on the highway. I also have Ace rock rails, Ace steel bumper and Warn winch killing my mileage l. Best mileage I’ve ever gotten was no doors or top on all gravel roads for about 70 miles. Got 20mpg and average speed of 25mph. I’m thinking 4.88 or 5.13 gearing. I tow and haul and where I am is reasonably hilly. Sounds like you’ll be fine. Good luck.
I have Smittybilt XRC2 front bumper, 12,000 lb winch, MetalCloak fenders, custom built rear bumper with dual swing outs/tire carrier and a JCR full height bed rack (no tent mounted right now) so I’m as heavy if not heavier than you. Again, very interesting how different everyone’s experience is and how different driving styles may play into things. I’ve gotten 21 mpg on a tank, but never the 24+ that some Sport and Overland owners tout. I plan to re-gear but I don’t need or want 2500+ RPM on the highway in 6th gear. Might as well just drive in 5th if that was the case.
 
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Jt-wrx

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I have Smittybilt XRC2 front bumper, 12,000 lb winch, MetalCloak fenders, custom built rear bumper with dual swing outs/tire carrier and a JCR full height bed rack (no tent mounted right now) so I’m as heavy if not heavier than you. Again, very interesting how different everyone’s experience is and how different driving styles may play into things. I’ve gotten 21 mpg on a tank, but never the 24+ that some Sport and Overland owners tout. I plan to re-gear but I don’t need or want 2500+ RPM on the highway in 6th gear. Might as well just drive in 5th if that was the case.
don't waste your time with 4.56, it'll be more like touching yourself vs actually being with a partner...good but not quite as good as it can be ;)

seriously though, you've got pretty much got full crew of 5 big dudes already bolted onto your rig and more coming...you will want to be 4.88 at minimum with all that extra weight on board, this is why i brought it up, my rig is a sports car...but i added pretty much nothing and started with the lightest version going, if you're loaded up rubicon plus all that added weight, then adding people, the tent and even more gear? i rarely suggest 5.13's for 37's but i think for these trail built up overland crawlers the 5.13 makes more and more sense, i bet you'll be sitting 500-800 lbs heavier than i am, my rig is 5150 lbs full of gas without me in it, plain jane sport s with mopar lift and that factory 30 lb bumper, the overland running boards are about 10 lbs each and the tonneau cover maybe 20 lbs, i put a couple subs and amps under backseat but that's about it, go find a scale, fill up, and get across it...subtract your own weight and lets see where you shake out

also, 37's and 4.88's is very close to stock and remember going from 35's up to 37's is a good jump in drag and rolling mass, you'll feel that quite a bit, and this is where the 4.88's even the losses, now add all the weight you're adding....ya, it's between 4.88's and 5.13's, 4.56's don't enter the discussion anymore, this is expensive enough to do it right the first time
 

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don't waste your time with 4.56, it'll be more like touching yourself vs actually being with a partner...good but not quite as good as it can be ;)

seriously though, you've got pretty much got full crew of 5 big dudes already bolted onto your rig and more coming...you will want to be 4.88 at minimum with all that extra weight on board, this is why i brought it up, my rig is a sports car...but i added pretty much nothing and started with the lightest version going, if you're loaded up rubicon plus all that added weight, then adding people, the tent and even more gear? i rarely suggest 5.13's for 37's but i think for these trail built up overland crawlers the 5.13 makes more and more sense, i bet you'll be sitting 500-800 lbs heavier than i am, my rig is 5150 lbs full of gas without me in it, plain jane sport s with mopar lift and that factory 30 lb bumper, the overland running boards are about 10 lbs each and the tonneau cover maybe 20 lbs, i put a couple subs and amps under backseat but that's about it, go find a scale, fill up, and get across it...subtract your own weight and lets see where you shake out

also, 37's and 4.88's is very close to stock and remember going from 35's up to 37's is a good jump in drag and rolling mass, you'll feel that quite a bit, and this is where the 4.88's even the losses, now add all the weight you're adding....ya, it's between 4.88's and 5.13's, 4.56's don't enter the discussion anymore, this is expensive enough to do it right the first time
I think it all depends on what chart you look at and I like my ride now on 35's. I don't actually have much complaint except in some hill climbs on the highway...I should mention that I am tuned too. Gibson exhaust and a Pulsar. The Pulsar doesn't add much in economy tune, but the tow tune and performance tune (91+ octane) are noticeable. I drive in economy most of the time and I appreciate the extra mpg's. I think the conversation about gears is almost the same as angry eyes grills (gross in my opinion) but to each their own. We all build our rigs for our tastes and needs. I have zero desire to run 2,500+ rpms on the highway. You essentially are losing your overdrive gear when you do that. As many have said, the 6 spd MT is essentially a 4 spd with 2 overdrives as the AT is a 6 spd with 2 overdrives. I should know by this coming weekend how bad the 37's are on the stock gears, but I'm gonna drive until I decide what I want to go with. 32,000 miles on my JTR already, I'm pretty comfortable with how it drives. I also almost never have anyone in the truck with me, so even on trips not going to worry about the weight of the family and I am debating deleting the rear seats with the Goose Gear setup (apparently the rear seats are pretty heavy).
 


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Jt-wrx

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ya if you're tuning allows enough power under 2500 to spin everything and the weight you're going to push around then go for it, i think you've done plenty of research now and will know what to look for, sounds like you're going to add some weight and drag still with tents and the rest of the camping gear but also consider who/what else will be in the cab, with decent aero(for a jeep) my jeep pulls decent power down the highway from 23-2400 rpm untuned and i'm skinny, i don't have giant tires sticking out into the wind, tread edge right at edge of fender if looking down from above and i have minimal weight on board, like this it's a sports car, but i was awful glad for the 4.88's when 3 paddle boards strapped to roof, kids and camping gear with trailer on board and headed down the highway at about 8930 lbs on the scale, maybe with good tune i could get away with 4.56 and i'm sure i could, it would be light years better than either of the stock options, if towing isn't really part of the plan and everything will be on the jeep...sounds like 4.56 may be the right compromise for you as i'd guess you'll be +-6000 lbs on the scale
 

cgflyer

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I run to the dump with a trash trailer regularly but I can't pinpoint a very accurate truck weight. I definitely added a bunch of weight, but I was pretty shocked at how much the factory rear bumper and hitch weighed. I actually don't think I added much with my setup as it eliminates a lot of steel from the hitch. The front bumper and winch was probably the biggest add. My rack is surprisingly only 80lbs, but once loaded with cooler and such, the truck will be heavy. I have a hard shell RTT coming which I hope will help with aerodynamics, but then my gobi rack that is coming will take that away haha...AND I may end up hating the 37's on the 4.10 so much that 4.56 may go out the window fast, but I don't mind having 6th as an overdrive like it is now.
 
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Jt-wrx

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my stock sport s bumper with all trim bits about 35 lbs, i tried a fab fours stubby with guard that was 88 lbs...i'm guessing the steel rubi bumper will be heavier than the sport so call it 50 and most winches run over 100, wouldn't be hard to believe you've added 150-200 lb to the nose end, i went back to my sport bumper as my theme for this 'truck' was always to be 'stock plus', i tend to drive pretty offensively as my method of being defensive ;), goals achieved, she's a snorty little stump puller

bone stock my base sport s with hard top, tow package, cold weather group came in on the scale at 4617 lbs full of gas without me in it, now i'm at just under 5150 lbs, from what a read pretty loaded rubicons would start up to 500 lbs heavier, i added overland running boards, rubber bed mat, access cover (all 3 of them added up to 70 lbs), i have about 50 lbs in tools/gear that ride in the box, the rest is lift/tires and the two subs under the back seat and maybe some coveralls/boots and misc. gear i stash in the cubbies, and some rigid lighting, a thin 10" lightbar on top of bumper, 3" pods replaced foglights and a small one cut into bumper beside license plate tied into bed lights, in total i've added 529 lbs with building it like a mountain backpacker minimalist mindset from the start...the weight adds up so quickly and easily, my overland strategy would be to simply buy backpacking gear and throw in the box, to keep the rig as light and nimble and lowest c of g possible, but i am a minimalist that way from years of chasing sheep in the mountains living off my back and it might be nice to just leave it out for the other 99% of the time as well as also being able to drive away from camp and come back to it? each there own there, i don't want camp attached to the rig fulltime, only if i planned for several months true overlanding would i consider that route and then add weight in the winch/protection stuff due to necessity although i'd still build it light as possible as it's in my dna

i wanted to keep the sport in my sport ;)

my build https://z-p42.www.instagram.com/gladiatoryyc/?hl=en
 

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I have an overland m/t. Thinking of jumping up from the 32.1 stock size to some 34.3 size tires. I just moved to a very hilly/mountain area. I already kind of think the 3.73 gears aren’t enough for the area, and while I want to get a little larger tire, I’m looking for some advise .
Should I go 4.56 or 4.88?
 
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Jt-wrx

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You’ve got some reading to do I guess, you’ll have it figured out in a week or so

 

 
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