Gearing Question For Automatic
04-09-2008, 09:48 PM
#11
JK Enthusiast
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True. However, an automatic X with 4.1 axle ratio's are better than you may think. it would still need better gears for the 35s.
For my automatic 2007 X:
Crawl ratio = 1st gear X t-case X diff X 2
Crawl Ratio = 2.84 x 2.72 x 4.1 x 2
Crawl ratio = 63.34:1
Manual:
Crawl = 4.34 x 2.72 X 3.21
Crawl = 37.89 (or 48.4 with optional 4.1)
For my automatic 2007 X:
Crawl ratio = 1st gear X t-case X diff X 2
Crawl Ratio = 2.84 x 2.72 x 4.1 x 2
Crawl ratio = 63.34:1
Manual:
Crawl = 4.34 x 2.72 X 3.21
Crawl = 37.89 (or 48.4 with optional 4.1)
Where do you get the "2" from in the automatic calculation?
I would recommend 5.13's with an Auto.
04-09-2008, 09:52 PM
#12
JK Enthusiast
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04-09-2008, 11:22 PM
#14
JK Super Freak
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I have an Unlimited X (automatic) and plan on running 35's. It's a daily driver and will see moderate trail use. I will also be taking several 10 hour roadtrips per year. Any good ideas about what will work better 4.88's or 5.13's??
Any help or insight will be greatly appreciated.
2008 Black X Unlimited
Future Plans: 2.5 Teraflex, 35x12.5x17 BFG M/T's, 4.88 or 5.13 Gears and lots of underbody armor!!
Any help or insight will be greatly appreciated.
2008 Black X Unlimited
Future Plans: 2.5 Teraflex, 35x12.5x17 BFG M/T's, 4.88 or 5.13 Gears and lots of underbody armor!!
I just got mine back from the shop and can tell you also, dont' waste time with the 4.88s. I got 5.13 with my auto and 35s. I wouldn't want any less for sure. My rpms were just under 2500 at 70MPH(by GPS)
04-10-2008, 05:31 AM
#16
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04-10-2008, 05:45 AM
#17
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I really appreciate all the advice and personal knowledge. I am definitely going with the 5.13's!! The Hypertech sounds good too. But all other MODS will have to wait after the the lift, tires and gears. My wife is armed and dangerous and I really don't want to piss her off more than once a year!! So, CAI, exhaust, bumpers and body armor will have to wait another year.
Thanks again, All.
2008 Black X Unlimited
Thanks again, All.
2008 Black X Unlimited
04-10-2008, 07:19 AM
#18
JK Enthusiast
04-10-2008, 07:45 AM
#19
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The torque converter multiplies off-idle torque be 2 to 3x. Since I don't know the exact value for the JK tranny, I used 2x.
Where big tires on a stock jk kill you the most of course is in 3rd gear (1:1) or overdrive (0.67:1)
Edit: Look on page 136 of the 4-Wheelers bible, plus here is a pretty good site on explaining crawl ratios including auto transmissions webejeepin.com/Gears.htm
Last edited by Blue; 04-10-2008 at 08:12 AM.
04-10-2008, 08:37 AM
#20
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Wow. Glad I came across this post. Just got off the phone with Dave at Northridge and I'll be getting the gears and an OME lift here in a few weeks.
Last edited by ArM4ND; 04-10-2008 at 08:41 AM.