Almost4x4

Posted: **Wed Apr 27, 2011 1:35 pm**

Installing larger tires degrades performace. Below is a chart that helps if one wants to regain that performance by re-gearing the ring and pinion differential gears.

http://www.4lo.com/calc/geartable.htm

Gear Ratio & Tire Size Chart

Good "rule of thumb" calculation is to mutiply .12 by your tire diameter. (.12 X 38" = 4.56)
[SIZE=-2](see more formulas at bottom of page)[/SIZE]
[SIZE=-1]The below table can be used to get a rough idea on gear ratios. The colors represent ideal RPM's at highway speeds (65). For highway cruising and best fuel economy stay towards the yellow (2600 rpm), around town daily driving is color coded green (2800 rpm), and for better towing power or just more 4-low power use the ratios near the red (3100 rpm). These calculations are assuming a manual transmission with a 1:1 ratio. If you drive an automatic your RPMs will be slightly higher, and the opposite is true if you have overdrive (your RPMs will be slightly lower).[/SIZE]

Better Gas Mileage Near Factory Ratio More Power
Gear RatioT
i
r
e

D
i
a
m
e
t
e
r
3.313.423.553.733.914.114.274.564.885.135.295.385.716.177.1727"26772766287230173163332534543689394741504279435246194991580028"25822668276929093050320633313557380640014126419644544813559329"24932576267428092945309532163434367538633984405243004647540030"24102490258427152846299231093320355337353851391741574492522031"23322409250126282755289630083213383836143727379040234347505132"22592334242325462696280529143112333135013610367238974211489433"21912263234924692588272028263018323033953501356137794093474534"21262197228023962512264027432929313532953398345636683963460635"20652134221523282440256526642845304532013301335735633850447436"20082075215422632372249325902766296131123209326434643743435037"19542019209522032308242625202692288130283123317633703642424338"19021966204021442247236224542621280529483040309232823546412139"18541915198820892190230223912554273328732962301331983455401540"18071867193820372135224423312490266428012888293731183369391541"17631822189119872083218922752429259927332818286630423287381942"17211778184619402033213722202371253826682751279829693208372843"16811737180318941986208721692316247926062687273329003134364244"164316981762185119412040211922632422254626262670283430633559
Common gear formulas:
Gear Ratio

Crawl Ratio

P-Metric to Inch Diameter

Tire Change (find new gear ratio)

Speedometer Adjuster (with oversize tires)
(New Tire Diameter / Old Tire Diameter) * Speedometer MPH = Actual MPH Simple Gear Ratio Formula
Ring Gear Teeth Count / Pinion Gear Teeth = Gear Ratio

Posted: **Wed Apr 27, 2011 1:50 pm**

wow googloid, you are on overdrive today :) nice post. lotsa info.

Posted: **Wed Apr 27, 2011 1:53 pm**

Indy;4239 wrote:wow googloid, you are on overdrive today :) nice post. lotsa info.

Hahaha Indy... Allowing all to benefit from the research for my rig. I am going to 4.56 from 3.73. That will give me a little more power, but highway mpg will suffer just a lil bit :)

Posted: **Wed Apr 27, 2011 1:57 pm**

Good calculators can be found here as well:

http://www.4lo.com/4LoCalc.htm

Posted: **Wed Apr 27, 2011 1:59 pm**

Nice research googloid, I think better to go for 4.27 instead and your car will be just like factory which mean alot of power to handle..lolz

Posted: **Thu Apr 28, 2011 3:27 am**

hehe! very nice post! also the calculators are great!
check the home page for the site and you will find this written there to the right side:
What is better than a Jeep? How about two jeeps!

again thanks for the valuable post