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

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
 
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.
 
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.
Click to expand...
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.

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

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

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

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 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.
Click to expand...

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.
 
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.
Click to expand...

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.
 
Last edited:
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.
 
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.
Click to expand...

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.
Click to expand...

Yup, this is what I was thinking.
 
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.
Click to expand...

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



Yup, this is what I was thinking.
Click to expand...

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?
 
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?
Click to expand...

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

Sent from my SM-G955U using WAYALIFE mobile app
 
You must log in or register to reply here.
Top Bottom