Originally Posted by Odd is he
As some of you may know, I took a chunk out of my ring gear in my rear end while "snow drifting"
a week ago.... So I decided to just go ahead and order 4.56 gears for my front and rear..... I'm running 35" shoes on my heep also....
My question is, will the gears be retardedly low? how 4low gonna be? How much am I looking at my speedo being off by with the stock speedo gear?
4.56s are not too low. If it were mine I would run 4.88s or 5.13s, depending on which transmission you have. If I had re-geared my Rubicon, I would have installed 4.88s....and it only had 33s.
As far as your speedometer error, divide your current ratio by the 4.56 which will give you a number indicating the percentage by which your speedo will change.
If your current gears are 3.73s............
3.73/4.56 = .82
Which means that the 3.73s are 82% of the 4.56s or that the 4.56s are 18% lower than the 3.73s and the speedometer will indicate 18% faster than it did before.
At an actual speed of 65 the speedometer would be indicating 77 mph.
Of course your 35 inch tires also play into the equation........
If you had 30 inch tires stock......
The circumference of a 30 inch tire is 94 inches. For a 35 inch tire it is 110 inches.
Dividing 94/110 = .85 or 85%
So the 35 inch tires reduced your overall speedometer indication by 15% and the gears increased it by 18% which results in a net change of a 3% increase in indicated speed over stock.
65 mph X 1.03 = 67 mph
One thing to remember when selecting gears..........
Peak torque on you 4.0 liter is rated at approximately 3200 rpm. This is the point on the torque curve with the lowest Brake Specific Fuel Consumption, which simply means your engine burns less fuel per horsepower here than at any other spot on the curve. Because of this fact, you can sometimes
increase fuel mileage by going to lower gears....... You also get a peppier more powerful vehicle on the highway in overdrive. It is for this reason that the first performance enhancing mod you should make is to re-gear. It is the best bang for the buck you can spend.
Food for thought.