35s & 4.56 gears experience

[syreeves]

Not sure if this info already made it to this thread but looks like Fiat already decided that 6MTs on 35s should run 4.88 gears. Gas Autos can get away with 4.56s...

https://www.motortrend.com/news/jeep-wrangler-xtreme-recon/

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[DanW]

Not sure if this info already made it to this thread but looks like Fiat already decided that 6MTs on 35s should run 4.88 gears. Gas Autos can get away with 4.56s...

https://www.motortrend.com/news/jeep-wrangler-xtreme-recon/

Actually, they did that as an option for bragging rights over the Bronco to get a 100:1 crawl ratio. 4.56 is the standard for Xtreme Recon with a manual and still gets you around 90:1. After living with 4.56 for awhile, I think it is perfect. I wouldn't want 1st or 6th to be any shorter. But glad they are offering 4.88. I think it'd be perfect for 37s or 35s in the mountains.

And it is no longer Fiat, but Stellantis. Or you could say Peugeot. ?

 

[syreeves]

Actually, they did that as an option for bragging rights over the Bronco to get a 100:1 crawl ratio. 4.56 is the standard for Xtreme Recon with a manual and still gets you around 90:1. After living with 4.56 for awhile, I think it is perfect. I wouldn't want 1st or 6th to be any shorter. But glad they are offering 4.88. I think it'd be perfect for 37s or 35s in the mountains.

And it is no longer Fiat, but Stellantis. Or you could say Peugeot. ?

Is it official that Stellantis (or whoever they are today ) has choosen to make 4.56 gears "standard" with the manual? The article from motortrend was pretty unambiguous: " Both the 392 and the Rubicon fitted with the Xtreme Recon package will benefit from 4.56:1 final drive gearing, while manual-equipped Rubicon models will get a 4.88:1 final drive ratio." On the other hand a car and driver article (https://www.caranddriver.com/news/a...-xtreme-recon-package-goes-sasquatch-hunting/) seems equally unambiguous that 4.88s will merely be available as an option on 6MTs... " For those who prefer to row their own gears, Rubicons equipped with the six-speed manual transmission can be optioned with 4:88.1 gearing that enables a crawl ratio of 100:1."

If I regear (after my warranty runs of course) then I'd prefer to go with 4.56s if possible. I'm looking for mileage and useable daily power with occasional towing - no drag strips or truck pulls in my future...

 

[ghost03]

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.

Is there a different housing and carrier needed for the regear?

 

[DanW]

Is there a different housing and carrier needed for the regear?

Just the rings/pinions and installation kit.

I have Dana 4.56 gears in my JL and they've been great. Mine is a manual, so I did it to re-gain the practical use of 6th gear, which was too tall with my 35's. I took a small hit with gas mileage, but I can now pass in 6th gear and hold speed on slight hills.

I had an excellent mechanic install it. For Fox Sake just south of Indianapolis. He set them up perfectly. Highly recommended for anyone in Indiana or nearby.

But if I had the auto in my JL, I would not have done it. My JT performs perfectly with 35's and 4.10 axles. It cruises on flat highways no problem in 8th gear and even on mild hills and gets as good gas mileage as my JL did when it was on stock 33's and 4.10 gears. I easily average 21mpg and sometimes hit 22. I'm amazed by that every time I drive it. The JL does get better mileage when towing my 3000lb boat, though.

 

[ghost03]

Just the rings/pinions and installation kit.

I have Dana 4.56 gears in my JL and they've been great. Mine is a manual, so I did it to re-gain the practical use of 6th gear, which was too tall with my 35's. I took a small hit with gas mileage, but I can now pass in 6th gear and hold speed on slight hills.

I had an excellent mechanic install it. For Fox Sake just south of Indianapolis. He set them up perfectly. Highly recommended for anyone in Indiana or nearby.

But if I had the auto in my JL, I would not have done it. My JT performs perfectly with 35's and 4.10 axles. It cruises on flat highways no problem in 8th gear and even on mild hills and gets as good gas mileage as my JL did when it was on stock 33's and 4.10 gears. I easily average 21mpg and sometimes hit 22. I'm amazed by that every time I drive it. The JL does get better mileage when towing my 3000lb boat, though.

I have a good Jeep guy doing mine, he has tons of experience, just not with JT’s he asked me to check if there was a carrier break for the JT. It has been crazy trying to find the answer. I just bought the Dana splicer 4.56 because I drove Atlanta to Missouri with a trailer and never made it out of 6 th gear. I went to a gear calculator and the best ratio for my application was 4.56. @ 2400 rpms at 80 mph.
I have a 2020 JT sport s, with a 3 1/2in lift running 35 Nitto ridge grippers. Thanks for the help.

 

[Wheelin98TJ]

I have a good Jeep guy doing mine, he has tons of experience, just not with JT’s he asked me to check if there was a carrier break for the JT. It has been crazy trying to find the answer. I just bought the Dana splicer 4.56 because I drove Atlanta to Missouri with a trailer and never made it out of 6 th gear. I went to a gear calculator and the best ratio for my application was 4.56. @ 2400 rpms at 80 mph.
I have a 2020 JT sport s, with a 3 1/2in lift running 35 Nitto ridge grippers. Thanks for the help.

No carrier break for the Dana Advantek axles.

 

[DanW]

I have a good Jeep guy doing mine, he has tons of experience, just not with JT’s he asked me to check if there was a carrier break for the JT. It has been crazy trying to find the answer. I just bought the Dana splicer 4.56 because I drove Atlanta to Missouri with a trailer and never made it out of 6 th gear. I went to a gear calculator and the best ratio for my application was 4.56. @ 2400 rpms at 80 mph.
I have a 2020 JT sport s, with a 3 1/2in lift running 35 Nitto ridge grippers. Thanks for the help.

My JL was the first M220 Sean Fox did, so if your guy is experienced, should be a piece of cake. There are differences from the JK, but he said it wasn't hard.

 

[holdyfolds]

Just wanted to say thanks to everyone who chimed in on these. Still helping people to this day. Because of this thread and a handful of others, now I know I'm going to get 4.56 gears for the 6 speed m/t and 35s.

 

[DanW]

Just wanted to say thanks to everyone who chimed in on these. Still helping people to this day. Because of this thread and a handful of others, now I know I'm going to get 4.56 gears for the 6 speed m/t and 35s.

I think you'll love it. 4.88 would just give you too many rpms on the highway. You'd wish you had a 7th gear. I think with the JT, 4.56 will be an even better match than on the JL because the JT is a little heavier.

 

[holdyfolds]

I think you'll love it. 4.88 would just give you too many rpms on the highway. You'd wish you had a 7th gear. I think with the JT, 4.56 will be an even better match than on the JL because the JT is a little heavier.

I believe it. I had an 06 wrangler 4.0 years back I dumped way too much time and money into. It had a 6 speed m/t and 3.07 gears. Was absolutely awful with 33s. Changed to a 4.10 and it was night and day difference and still probably could have gone with 4.56. The JT stock wheels and tires with 3.73 gears reminds me of the wrangler with 33's and 3.07 gears. I can imagine why people complain about JT's with 35s and 3.73 gearing.

 

[addy003]

Just the rings/pinions and installation kit.

I have Dana 4.56 gears in my JL and they've been great. Mine is a manual, so I did it to re-gain the practical use of 6th gear, which was too tall with my 35's. I took a small hit with gas mileage, but I can now pass in 6th gear and hold speed on slight hills.

I had an excellent mechanic install it. For Fox Sake just south of Indianapolis. He set them up perfectly. Highly recommended for anyone in Indiana or nearby.

But if I had the auto in my JL, I would not have done it. My JT performs perfectly with 35's and 4.10 axles. It cruises on flat highways no problem in 8th gear and even on mild hills and gets as good gas mileage as my JL did when it was on stock 33's and 4.10 gears. I easily average 21mpg and sometimes hit 22. I'm amazed by that every time I drive it. The JL does get better mileage when towing my 3000lb boat, though.

Great to hear that For Fox Sake is reputable; I have them earmarked for regear when I get around to it. I'm in north Indy for a few years.

 

[DanW]

Great to hear that For Fox Sake is reputable; I have them earmarked for regear when I get around to it. I'm in north Indy for a few years.

Keep us posted if you get it done, and on your build!

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