Do Yourself a Favor - Regear Your 2012-Up JK!!

Draconianwinter · Mar 27, 2017

Will be going 4.88 on mine here soon I think. Should bring back to the same power ratio I had when running the stock tires on my rubi though personally do far it really hasn't been that bad, but will know more after this coming weekend when I go up to windrock.

sent from your basement

WJCO · Jan 3, 2018

Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

BaddestCross · Jan 3, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

I can't speak to those ratios specifically, but I can tell you that the tire/gear chart floating around is pretty damn accurate. It was spot on with my 4.10s, but I haven't checked with my 5.13s yet. 315s are metric 35s, so take a look...

With the time I was able to actually drive with the 5.13s, I can tell you I'm super happy with the performance on the highway and I've gained back at least 1.5mpgs.

However, since you're in a sport, you probably don't want to go lower than 4.88 with your D30.

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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

Gbint · Jan 3, 2018

I’m running those shitty 3.21’s. would love to go at least up one more to 3.73 or 4.10. Soon as the warranty is up.

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Ryangriffiths2252 · Jan 3, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

Hey, I run a set of 5.13 gear in my ‘08 jk. I wouldn’t recommend going this low but tbh as long as you aren’t doing a lot of hwy miles (above 75mph) it isn’t too bad. It will destroy your mpg’s though. I get a solid 12.5 to 14 mpg with mixed city and highway driving.

Thanks,
Ryan

BaddestCross · Jan 3, 2018

Ryangriffiths2252 said:
Hey, I run a set of 5.13 gear in my ‘08 jk. I wouldn’t recommend going this low but tbh as long as you aren’t doing a lot of hwy miles (above 75mph) it isn’t too bad. It will destroy your mpg’s though. I get a solid 12.5 to 14 mpg with mixed city and highway driving.

Thanks,
Ryan

Lol. I was getting 9-10mpg with my 4.10s on 35s. You're doing pretty damn good.

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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

Ryangriffiths2252 · Jan 3, 2018

Yeah ive got 35s too but im in a two door so maybe the weight helps

*

Thanks,
Ryan

BaddestCross · Jan 3, 2018

Ryangriffiths2252 said:
Yeah ive got 35s too but im in a two door so maybe the weight helps *

Thanks,
Ryan

I'm also in a 2 door but she is a pig.

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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

Brute · Jan 3, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

My Brute is 4.88 with 37's...2700 rpm at 70 mph (5.7 Hemi); my Anvil is 4:56 with 35's...2650 at 70 mph (5.7 Hemi); both get about 14 mpg Hwy...

WJCO · Jan 3, 2018

Brute said:
My Brute is 4.88 with 37's...2700 rpm at 70 mph (5.7 Hemi); my Anvil is 4:56 with 35's...2650 at 70 mph (5.7 Hemi); both get about 14 mpg Hwy...

Hey showoff, I said 3.8L

wayoflife · Jan 3, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

What year is your sport again? Early on, 4.10's came standard on any JK with a tow package. Even if you don't, I'm pretty sure that 3.73 came on JK's with limited slip. That being said, 315 is bigger than an advertised 35 and I personally would recommend 4.88 with them. Assuming you do have 4.10, 4.56 is too close of a ratio to even waste your time and money on. I ran 5.13 with 35's and was running over 3k at 70 MPH. 4.88's should put you at around 2500 which to me is where you want to be.

WJCO · Jan 3, 2018

wayoflife said:
What year is your sport again? Early on, 4.10's came standard on any JK with a tow package. Even if you don't, I'm pretty sure that 3.73 came on JK's with limited slip. That being said, 315 is bigger than an advertised 35 and I personally would recommend 4.88 with them. Assuming you do have 4.10, 4.56 is too close of a ratio to even waste your time and money on. I ran 5.13 with 35's and was running over 3k at 70 MPH. 4.88's should put you at around 2500 which to me is where you want to be.

It's a 2011 and does have a factory hitch. I'll go out in a minute and actually check the gear ratio. I haven't done that yet.

EDIT: It has 3.73s.

MSJKU11 · Jan 3, 2018

I have a JKU 2011 auto sport on 315s. After upgrading to 4.88 I'm around 2400-2500 rpms at 70mph. My mpg mixed is around 15mpg. I haven't taken a road trip yet but I do a lot of city driving. Hope this helps.

wayoflife · Jan 3, 2018

WJCO said:
It's a 2011 and does have a factory hitch. I'll go out in a minute and actually check the gear ratio. I haven't done that yet.

EDIT: It has 3.73s.

Yeah, I'm pretty sure 4.10 only came standard in 2007.

MSJKU11 said:
I have a JKU 2011 auto sport on 315s. After upgrading to 4.88 I'm around 2400-2500 rpms at 70mph. My mpg mixed is around 15mpg. I haven't taken a road trip yet but I do a lot of city driving. Hope this helps.

Yup, this is what I was thinking.

WJCO · Jan 3, 2018

MSJKU11 said:
I have a JKU 2011 auto sport on 315s. After upgrading to 4.88 I'm around 2400-2500 rpms at 70mph. My mpg mixed is around 15mpg. I haven't taken a road trip yet but I do a lot of city driving. Hope this helps.

wayoflife said:
Yeah, I'm pretty sure 4.10 only came standard in 2007.

Yup, this is what I was thinking.

This helps. Thank you both. Being that we have 3.73s (which I didn't expect), I'll definitely go up to 4.88s. Not worth spending the money and time for 4.56s based on that fact. Also, I assume that with 3.73s, I can re-use my old Dana 30 front carrier correct?

wayoflife · Jan 3, 2018

WJCO said:
This helps. Thank you both. Being that we have 3.73s (which I didn't expect), I'll definitely go up to 4.88s. Not worth spending the money and time for 4.56s based on that fact. Also, I assume that with 3.73s, I can re-use my old Dana 30 front carrier correct?

Correct. You would have needed to get a new carrier if you were running 3.21.

WJCO · Jan 3, 2018

wayoflife said:
Correct. You would have needed to get a new carrier if you were running 3.21.

:thumb: :beer:

Saharaunlmtd · Jan 3, 2018

WJCO said:
Hey showoff, I said 3.8L

Lol...

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TRLJNKY · Jan 3, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

Im running 4.10's as a daily driver with 315's (Sahara). Its a pig constantly searching for gears on the hwy. I have to switch the OD off with any incline or head wind. I run about 1900 rpms at 70. I wont hesitate to put 4.88's. I dont think 4.56's will be cost effective for the reward. At least for me. Will be interesting to see what you decide though.

aka cavfighter

Draconianwinter · Jan 6, 2018

WJCO said:
Question for the 3.8l jeepers running 4.56 or 4.88 with an automatic. What rpms are you seeing around 70-80 mph? We're going to regear soon and install 315s. Being that this jeep is a daily driver and roadtripper, I'm hesitant running 4.88s vs 4.56s if we can see some better mpg on long trips. We have a sport, so I assume we have 3.21s now.

I was going to say 4.56 then I noticed you have the 3.8l. I have the 3.6l with a straight shift and running 4.88 in mine. Average around 16 mpg. The 4.88 was actually a little lower gearing than I needed, but I chose the 4.88 due to trail riding. I also seldom run over 70 mph. Normally I stay astound 65 mph. Just never really in a hurry when I am in my jeep.

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