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5.38s with 37s

Duece McCracken

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It is a night and day difference. The manual makes it worse.
4LO it was fine even on 3.73s, but there were times where starting in 1st pointing uphill on dirt in 4HI that it was either stall, slip the clutch alot or rooster tails.
5th gear was a downhill only thing. After the regear, once I hit 60-65 I can put it in 6th and set the cruise and never think about it again. Around town gas mileage went up about 10%. It's still a brick, so >75mph the mileage is bad, but at 65 I've seen 20 over a 2 hour trip.
Ahhhh, im a manual Rubicon, so 4.10s. My 5th and 6th is pretty useless now, cant imagine 3.73's and 37" tires, lol!!

Thank you for the reply! I'm still trying to figure out what ratio I want.
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Ahhhh, im a manual Rubicon, so 4.10s. My 5th and 6th is pretty useless now, cant imagine 3.73's and 37" tires, lol!!

Thank you for the reply! I'm still trying to figure out what ratio I want.
If you are going to be running 37's, and 80 is about as fast as you'll ever run, 4.88s and 5.13s are splitting atoms. ~100-150rpm different in 6th at any speed. There are times I look for a 7th gear, but we run 80+ on the turnpikes out here. 4.88s in 5th are close to 5.13s in 6th, and offroad, the 4:1 transfercase fixes everything else.
 

Duece McCracken

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If you are going to be running 37's, and 80 is about as fast as you'll ever run, 4.88s and 5.13s are splitting atoms. ~100-150rpm different in 6th at any speed. There are times I look for a 7th gear, but we run 80+ on the turnpikes out here. 4.88s in 5th are close to 5.13s in 6th, and offroad, the 4:1 transfercase fixes everything else.
Ahhhh!

I still have to sort out if im going 35", or 37", lift size, then iron out the gearing. 5.13 seems like the minimum I will go. More research may lock me into a selection.

Its just a bit tougher to find info from just the manual drivers. Keep finding autotradgic info. Lol
 

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Ahhhh!

I still have to sort out if im going 35", or 37", lift size, then iron out the gearing. 5.13 seems like the minimum I will go. More research may lock me into a selection.

Its just a bit tougher to find info from just the manual drivers. Keep finding autotradgic info. Lol
5.13s on 35's would be geared pretty deep. If you tow, it would make sense, but for daily driving it's extremely agressive. I'm pretty gear sensitive, and sometimes think I might have been happier with 4.88s. But I don't tow anything, and still run pretty light. What speed does traffic flow in PA?
 

Duece McCracken

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5.13s on 35's would be geared pretty deep. If you tow, it would make sense, but for daily driving it's extremely agressive. I'm pretty gear sensitive, and sometimes think I might have been happier with 4.88s. But I don't tow anything, and still run pretty light. What speed does traffic flow in PA?
Im normally 75-85mph. I find 5th and 6th pretty lame, I'll do the math to see what rpm I'd be at those speeds. As the truck drives stock, I want swapped gears in it, lmfao!
 

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hjdca

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I am running Dana Spicer 5:13s and 37's with a stick shift JTR for about 30K miles now. I think it is the perfect combination. I have never said, I wish I went with 4:88s, or 5:38s. My perception is that 5:13s are just perfect, and I live in a mountainous area around 2K elevation. The fastest I have gone is approx. 94 mph, plenty of gear for that. I do not tow.
Note: with the 4:1 Rubicon transfer case, granny gear is fantastic. No problems with the stock clutch, still strong. I am around 54K miles now.
 
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TheRealGinjaNinja

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Ahhhh!

I still have to sort out if im going 35", or 37", lift size, then iron out the gearing. 5.13 seems like the minimum I will go. More research may lock me into a selection.

Its just a bit tougher to find info from just the manual drivers. Keep finding autotradgic info. Lol
Prior to my JTM, I had a 6 speed JLUR on heavy 35s so I have 3.5 years experience with it. I was not happy at all on 35s with 4.10s. Had a shop and appointment lined up to regear it to 5.13s with the assumption I was sticking with 35s for a while with a potential for 37s down the road. But this was when I decided to trade it for the Mojave and never went through with it. IMO my 35s were a tad small on the Gladiator but looked fine on the Wrangler so was a bit more content with that choice. My Gladiator I know I am sticking with 37s it is perfect.

I think the advice here is solid. Manual or auto my conclusion was the same - sticking with 35s or ever downsizing to 35s someday, 5.13 is the way to go no question about it. 5.13 is pretty good for 37s as well so you have some comfort knowing you can change your mind between two popular tire sizes. If you know you will stick with 37s or larger and don't drive 85+ mph...5.38 and never look back!

Cheers
 
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TheRealGinjaNinja

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Updated numbers after 1,542 miles driven on steel wheels. I just installed the alloy wheels so this is all the data for this configuration. I will take pics of the RPMs so Iā€™m not going off memory and provide an update soon.

Data with 5.38 and steel wheels:
Average MPG - 12.60
Best MPG - 14.2
Worst MPG - 12.1
0-60 - 9.04
*** Note - this was done in the exact same spot as before for comparisons sake, but it is going up a slight incline and at 900 feet elevation. Flat ground 0-60 is a bit better (mid 8s)
 

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Updated numbers after 1,542 miles driven on steel wheels. I just installed the alloy wheels so this is all the data for this configuration. I will take pics of the RPMs so Iā€™m not going off memory and provide an update soon.

Data with 5.38 and steel wheels:
Average MPG - 12.60
Best MPG - 14.2
Worst MPG - 12.1
0-60 - 9.04
*** Note - this was done in the exact same spot as before for comparisons sake, but it is going up a slight incline and at 900 feet elevation. Flat ground 0-60 is a bit better (mid 8s)
Looking forward to the RPMā€™s and observations with alloy wheels. I have 5.13ā€™s and 37ā€™s. Have always felt I should have gone 5.38, so interested in your experience.
 

Panthers65

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I am running Dana Spicer 5:13s and 37's with a stick shift JTR for about 30K miles now. I think it is the perfect combination. I have never said, I wish I went with 4:88s, or 5:38s. My perception is that 5:13s are just perfect, and I live in a mountainous area around 2K elevation. The fastest I have gone is approx. 94 mph, plenty of gear for that. I do not tow.
Note: with the 4:1 Rubicon transfer case, granny gear is fantastic. No problems with the stock clutch, still strong. I am around 54K miles now.
Ordered my Dana 513's back in November. Front and the masters got in quick, finally got my eaton for the front yesterday, still waiting on the rear gears.

Dana's website says 16 weeks, hopefully since I ordered mine 8-12 weeks ago I don't have much longer to wait. If I hadn't gotten the front already I might ask them to switch back to 4.88's, but I have a feeling I"ll be happier in the long-run.


Did you/Anyone switch out Diff covers when you changed gears? Say a YT video of a shop that was commenting on how little diff fluid was with the stock covers, and moving to an aftermarket cover to increase capacity and add fins for better cooling was almost necessary with 5.13s and 5.38's.
 

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Panthers65

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Looking forward to the RPMā€™s and observations with alloy wheels. I have 5.13ā€™s and 37ā€™s. Have always felt I should have gone 5.38, so interested in your experience.
4.5% difference, It's not enough of a different to keep thinking about. Enjoy your current setup.
 

BearDog

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Good thread. I'm in east Texas, so different terrain. Running 37's now with auto and stock 4.10's. Light towing. Mostly town driving, with a few hwy trips now and then. Had planned on 5.13's this summer. Considering 40's in the future, so now wondering if 5.38's are the way to go.

Looking forward to your continued updates.
 

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4.5% difference, It's not enough of a different to keep thinking about. Enjoy your current setup.
Very true and they were fine when living in Atlanta. Now starting out at 6,200ā€™, every little bit helps with the 3.6 wheezing. Plus, the shop in Atlanta did a terrible job setting them up, so looking at replacing them anyway. Stay away from a shop that starts with ā€˜Fā€™ in Roswell. But overall agree, if I wasnā€™t already looking at replacement again, Iā€™d leave well enough alone.
 
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TheRealGinjaNinja

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Ordered my Dana 513's back in November. Front and the masters got in quick, finally got my eaton for the front yesterday, still waiting on the rear gears.

Dana's website says 16 weeks, hopefully since I ordered mine 8-12 weeks ago I don't have much longer to wait. If I hadn't gotten the front already I might ask them to switch back to 4.88's, but I have a feeling I"ll be happier in the long-run.


Did you/Anyone switch out Diff covers when you changed gears? Say a YT video of a shop that was commenting on how little diff fluid was with the stock covers, and moving to an aftermarket cover to increase capacity and add fins for better cooling was almost necessary with 5.13s and 5.38's.
I did not swap covers on mine. I didnā€™t get the sense it was an important upgrade for use case but I could certainly be wrong. If I was towing heavy or over payload capacity of the truck like a lot of the overlanders here, I would probably do them. Also, I have 2.5 ton steering on my Jeep so space is tight as it is.

Cheers
 
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TheRealGinjaNinja

TheRealGinjaNinja

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Good thread. I'm in east Texas, so different terrain. Running 37's now with auto and stock 4.10's. Light towing. Mostly town driving, with a few hwy trips now and then. Had planned on 5.13's this summer. Considering 40's in the future, so now wondering if 5.38's are the way to go.

Looking forward to your continued updates.
You guys in Texas are regularly going 85-90+mph on flat highways so something to consider. If 40s are happening I wouldnā€™t hesitate with 5.38s. What tire you running now?
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