Correct gear for 37's and manual

Diablo

Diablo

New member
Hello, I'm a new guy here and by the way, I really like your site, anyway, I'm running a 14 JKU Rubicon with a 6-speed and 37's. I bought a Dynatrac Pro Rock 44 case and will change gearing when I install it. My question to you THAT HAVE manual cases and 37's, what gear ratio would be best? I would like to keep as close to the factory rpm and speed as it was new. I see some running 4:88 and some 5:13's. Like I said, I'd like to be as close to factory rpm's.
Thanks in advance.
 
BlueBox

BlueBox

New member
I just went 5.13 with the same setup and have to say it's awesome. Haven't wheeled yet but the gears feel right where they should be. That said probably a bit lower than stock.
 
wayoflife

wayoflife

Administrator
Staff member
I don't know. With a 6-speed and a 3.6L motor, the correct ratio really would be 4.88's with a set of 37" tires. 5.13's might be nice if you have to do a lot of mountain climbing or if you just like to play on the rocks but at highway speeds, you'll be pushing measurably higher RPM's.
 
Diablo

Diablo

New member
Thanks for the replies,
Wayoflife, I've heard the same thing but wanted to get some real world advice from people running the same set up.
Troy-built and BlueBox, could you tell me your rpm's at 65 mph?
 
DWiggles

DWiggles

Caught the Bug
Diablo said:
Thanks for the replies,
Wayoflife, I've heard the same thing but wanted to get some real world advice from people running the same set up.
Troy-built and BlueBox, could you tell me your rpm's at 65 mph?
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I'm planning on 5.13, I have a 2015, 6 speed jku on 37" toyos. And I'm in texas. So LOTS of flat highway.
 
t8er

t8er

New member
2014 JKUR 6speed on 37" mud grapplers. I had the same debate and did 5.13's. I drove on with 4.88's and even though it's a little higher on the highway it's awesome off-road and in the mountains
 
Evil

Evil

New member
wayoflife said:
I don't know. With a 6-speed and a 3.6L motor, the correct ratio really would be 4.88's with a set of 37" tires. 5.13's might be nice if you have to do a lot of mountain climbing or if you just like to play on the rocks but at highway speeds, you'll be pushing measurably higher RPM's.
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From a 4.88 to a 5.13 on a 6 speed trans your only looking at roughly 200 RPMs more so if you want a little more throttle response go with the 5.13. My buddy just did 4.88's and we put on my old 37's and its OK but to me feels like it will crap out on a hill or trying to climb a steep grade.
 
BlueBox

BlueBox

New member
wayoflife said:
I don't know. With a 6-speed and a 3.6L motor, the correct ratio really would be 4.88's with a set of 37" tires. 5.13's might be nice if you have to do a lot of mountain climbing or if you just like to play on the rocks but at highway speeds, you'll be pushing measurably higher RPM's.
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Agreed. I'm at 3000 at 75mph. It's high but I drove around in 5th gear for a couple weeks on 35s with 4.10s to make sure I was ok with it. Looking forward to the benefits in the mtns.

I'll take a look what 65 mph works out to tomorrow.
 
Benito

Benito

Caught the Bug
i have a '13 6speed with 37's and 4.10s, there is a with for more power, however i can go down the highway just fine and even use 6th gear when its flat, hit 80mph+ on texas highways, i even think it still does really well crawling with the rubi transfer case. i am getting ready to regear with the front axle swap and am leaning towards 4.88s.
 
Diablo

Diablo

New member
The reason I'm asking is that I know the engine runs best at a certain rpm, temp and speed, like at work we trim an engine for standard day conditions (elevation-temp and pressure) and that's where it runs optimally. This is why I'm trying to get as close to the factory rpm and speed range as possible.
I really use the Jeep probably 3 or 4 times a year down south at Windrock and Jelico (easy trails) but use the hell out of it during bow season so I'd say 95% highway with about 5% offroad.
 
DWiggles

DWiggles

Caught the Bug
Diablo said:
I really use the Jeep probably 3 or 4 times a year down south at Windrock and Jelico (easy trails) but use the hell out of it during bow season so I'd say 95% highway with about 5% offroad.
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4.88 will put you closer to factory gearing
 
OverlanderJK

OverlanderJK

Resident Smartass
5.13's hand down. I run 5.13's with 35's and a six speed. I wouldn't want anything less.

Diablo said:
The reason I'm asking is that I know the engine runs best at a certain rpm, temp and speed, like at work we trim an engine for standard day conditions (elevation-temp and pressure) and that's where it runs optimally. This is why I'm trying to get as close to the factory rpm and speed range as possible.
I really use the Jeep probably 3 or 4 times a year down south at Windrock and Jelico (easy trails) but use the hell out of it during bow season so I'd say 95% highway with about 5% offroad.
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The 3.6L actually performs better at high RPM.
 
wayoflife

wayoflife

Administrator
Staff member
LOL!! I suppose it's just me having a JK running a 6.2L LS that cruises at about 1800-2400 RPM at 75+ MPH that makes my other JK running a 3.6L v6 running 3200-3500 seem a bit off. :crazyeyes:
 
Sharkey

Sharkey

Word Ninja
wayoflife said:
LOL!! I suppose it's just me having a JK running a 6.2L LS that cruises at about 1800-2400 RPM at 75+ MPH that makes my other JK running a 3.6L v6 running 3200-3500 seem a bit off. :crazyeyes:
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You sure have been rubbing that in lately haven't you Mr. V8 Fancy Pants. ;)
 
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