What Aftermarket gears on your 6sp 3.8 Jk with 35s
01-25-2016, 06:56 PM
#12
JK Freak
Thread Starter
I just had 4.88 installed on my 2011 6sp. I have Cooper "35's" which measure closer to 34.5".
You don't have to shift out of 6th on the highway except for very steap grades. Around town driving is fine, any type of downslope and you can start in second no problem. Also, doing a 1-3-5 shift works well with the new gears.
I am happy with the choice, but will probably go with slightly larger tires next time (true 35 or maybe a little larger) to help bring the rpms back down some. I am showing right around 2600 at 65. I think 4.56 would have been fine as well, and maybe sound like the better option for the driving you describe.
You don't have to shift out of 6th on the highway except for very steap grades. Around town driving is fine, any type of downslope and you can start in second no problem. Also, doing a 1-3-5 shift works well with the new gears.
I am happy with the choice, but will probably go with slightly larger tires next time (true 35 or maybe a little larger) to help bring the rpms back down some. I am showing right around 2600 at 65. I think 4.56 would have been fine as well, and maybe sound like the better option for the driving you describe.
01-25-2016, 07:00 PM
#13
JK Freak
Thread Starter
01-25-2016, 10:46 PM
#14
JK Jedi Master
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Search google or whatever for "jeep jk gear chart", you should get a page with a bunch of pics of colored graphs at the top. A member here by the name of Jpop designed these things a few years back, now they pop up on every jeep site out there. They are built for the JK, not generic charts, and are divided by engine type and transmission type, just find the right chart and plug in the numbers, using the "actual measured tire height", not the mfg spec.
But, for a 3.8 6spd, running 35" tires (that actually measure 34" under vehicle weight):
4.88 = 2837 rpm @ 70 mph
4.56 = 2651 rpm @ 70 mph
with 37's that measure 36":
4.88 = 2680 rpm @ 70 mph
And just for comparison, a bone stock 3.8 rubicon 6spd (4.10 and 32's that measure 31") should be right around 2650 rpm @ 70.
But, for a 3.8 6spd, running 35" tires (that actually measure 34" under vehicle weight):
4.88 = 2837 rpm @ 70 mph
4.56 = 2651 rpm @ 70 mph
with 37's that measure 36":
4.88 = 2680 rpm @ 70 mph
And just for comparison, a bone stock 3.8 rubicon 6spd (4.10 and 32's that measure 31") should be right around 2650 rpm @ 70.
01-29-2016, 05:07 PM
#16
I have an '11 Rubicon with 35's and 4.88 gears. It works well. I would not want 4.56 as it would not handle as well at high altitudes or crawl as well. With heavy bumpers and rock guards I have decent power/response. If your not hitting the trails or heading up into the mountains then 4.56 may work well for you.