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Gear swap before long road trip or wait?

chevymitchell

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I have a Sport with 35s and will be taking a 4000-5000 mile road trip out west in July. I currently have stock gearing. Would I be better off to swap gears now or after the trip? Looking to possibly save a little on fuel.
I would do the swap now. Out West, you're not only going to encounter many passes and hills to climb, but your Jeep will also be down on power and you will appreciate the return to a factory mechanical advantage. You'll see an increase of 1-2 mpg in your average, but again, you'll appreciate it the most when get into those mountain passes.

If you're considering 37's now or anytime in the future, run at least a 4.88. The 4.88 is close to factory mechanical advantage for a 37" tire. It's actually over-geared by a couple tenths.

Break-in isn't a myth, but it's also not as complicated or convoluted as decades of "black magic" may suggest. It's all about heat cycles, not necessarily load or shock load. I don't want the OP's thread to get hi-jacked by this tangent, but we can discuss in the axles section if anyone would like.

@UNC Rubicon and myself are also heading to Colorado and Utah in July; gonna be a great time.
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I will be there July 10-25 give or take a few days getting there and back from KY. I plan to be in Albuquerque, Grand Canyon, Vegas, Moab, Denver...
 

chevymitchell

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I will be there July 10-25 give or take a few days getting there and back from KY. I plan to be in Albuquerque, Grand Canyon, Vegas, Moab, Denver...
We leave NC on July 21 and head to Holy Cross, Moab, then back Ouray. Home Aug 4th. We'll miss each other it looks like, but have a safe trip and a good time.

If you have any questions on putting those gears in just give me a ring. I'll help ya through it. 3364429463.
 
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jdhunt0

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We leave NC on July 21 and head to Holy Cross, Moab, then back Ouray. Home Aug 4th. We'll miss each other it looks like, but have a safe trip and a good time.

If you have any questions on putting those gears in just give me a ring. I'll help ya through it. 3364429463.
Thanks, but this is something I think I'll pay a shop to do.
 

zeebo56

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Thanks, but this is something I think I'll pay a shop to do.
I had 4.88s with 35s for a little while before switching to 37s. 4.88s or 5.13 would be my choice. I don't do any towing or anything. I might do a little in the future. Highway it is a great balance.
 

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Seems like you'd have more than enough time to break them in and change the diff oil before your trip, and like it'd make the trip more enjoyable, so I'd go for it!
 

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I will be there July 10-25 give or take a few days getting there and back from KY. I plan to be in Albuquerque, Grand Canyon, Vegas, Moab, Denver...
We’re leaving KY for the NW in late July sometime from east of Louisville. We need to get on wrapping up our travel itinerary.
 
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jdhunt0

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We leave NC on July 21 and head to Holy Cross, Moab, then back Ouray. Home Aug 4th. We'll miss each other it looks like, but have a safe trip and a good time.

If you have any questions on putting those gears in just give me a ring. I'll help ya through it. 3364429463.
If I did decide to do it myself, what all parts do I need and what brand gears do you recomend? My JL has 31k miles on it now so everything should be in good shape.
 

chevymitchell

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If I did decide to do it myself, what all parts do I need and what brand gears do you recommend? My JL has 31k miles on it now so everything should be in good shape.
I'm a big fan of Dana parts in a Dana axle. They just set-up better and more consistent.

R&P
Master Install Kit
Gear Oil
Teflon Tape (Yellow)
Loctite (Red and Blue)
Programmer or pay dealer to update ratio/tire size

There are several write-ups in the Axles section you should review. A lot of people put out a lot of good info in that section for getting your gears done right.
 
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jdhunt0

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Am I going to hate 4.88s if I stick with 35s?
 

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chevymitchell

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Am I going to hate 4.88s if I stick with 35s?
If you're sticking to 35's, go with 4.56's.

The Jeep and 8-speed will run as close to stock and the way it was designed if you follow the math.

Hate it? Probably not. If 37's are ever a possibility, it would be cost effective to just go with the 4.88 now.
 

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Doing a long trip in June with ours and the kids and I specifically swapped from 410 to 513 for it. I’m running 37s.
So far, with about 600 miles on 513, I’m getting 4 mpg better city/highway combined.
 

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We leave NC on July 21 and head to Holy Cross, Moab, then back Ouray. Home Aug 4th. We'll miss each other it looks like, but have a safe trip and a good time.

If you have any questions on putting those gears in just give me a ring. I'll help ya through it. 3364429463.
If you are by Holy Cross, you should consider doing Red Cone Pass and Webster Pass loop..
 

Atom631

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Doing a long trip in June with ours and the kids and I specifically swapped from 410 to 513 for it. I’m running 37s.
So far, with about 600 miles on 513, I’m getting 4 mpg better city/highway combined.

What engine and what is your avg MPG now?
 

cmb396

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What engine and what is your avg MPG now?
3.6. Depends on whether I'm drivin, or my wife, lol. On a 150 mile trip through back roads, I got 22.8, mostly driving 45-55.
In town, around 18.
Her in town, around 15.
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