View Poll Results: Gearing for "High Speed JK"
4.56
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4.88
0
0%
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3.8L 6-Speed "High Speed JKs" with 35's 75-80 Mph
03-27-2017, 06:49 PM
#11
JK Junkie
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10.3: will very rarely be used because it is just too slow and your tires are just going to be too small to take advantage of the low crawl speed. 3.8 is what you will be using 90% of the time off road even on the hard stuff. and if you want to go a bit faster off road the 2.72 is an option but also rarely used. Save some weight and money and just do a 3.8, 4.3, or 5.0 2 speed.
jtphoto, you are correct that the atlas will do nothing for highway expect for some extra noise that the gears make vs a chain drive like the factory box.
jtphoto, you are correct that the atlas will do nothing for highway expect for some extra noise that the gears make vs a chain drive like the factory box.
03-27-2017, 06:52 PM
#12
JK Junkie
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At 208,000 miles on my Jeep, all over the U.S. (been to three of four corners and Alaska), having driven it from the Mexican border to the Arctic Ocean, I have quite a bit of experience with highway driving. 4.88s, 35s, very heavy (approaching 7K pounds). I guess "good gas mileage" is a matter of opinion. I generally keep my speed to 65 and below and, without wind and hills (honest, it's uphill both directions the roads I travel sometimes!) I get in the low-mid teens. I'm turning about 3K RPM at 70 MPH. Sometimes I go 75 MPH, but only very rarely faster (just briefly to pass). MPG drops a mile or two when I go that fast, and can even drop into single digits if the wind is against me.
03-27-2017, 07:17 PM
#13
JK Jedi
I am on 40's and only use 10:3 on extreme technical climbing like 4'-5' boulders, it moves so slow that I could put it into gear and get out and walk the trail, eat lunch and walk back to the jeep before it went 100'. You are going to need a big foot print to get the grip (stickies would be nice too) that the 10:3 offers. on small tires you are just going to sit there and spin them. You also won't be able to get any momentum to climb steeps like you need sometimes. Running in second is better but still pretty slow and is roughly the equivalent of running the 5:1 2 speed. If I had to do it all over again I would likely get the 5.0 2 speed over the 4 speed. You will also need a shorter front driveshaft with the 4 speed where I think you can get by with the factory length shaft for the 2 speed.
03-27-2017, 08:04 PM
#14
JK Junkie
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I am on 40's and only use 10:3 on extreme technical climbing like 4'-5' boulders, it moves so slow that I could put it into gear and get out and walk the trail, eat lunch and walk back to the jeep before it went 100'. You are going to need a big foot print to get the grip (stickies would be nice too) that the 10:3 offers. on small tires you are just going to sit there and spin them. You also won't be able to get any momentum to climb steeps like you need sometimes. Running in second is better but still pretty slow and is roughly the equivalent of running the 5:1 2 speed. If I had to do it all over again I would likely get the 5.0 2 speed over the 4 speed. You will also need a shorter front driveshaft with the 4 speed where I think you can get by with the factory length shaft for the 2 speed.
