Well-Known Member
I have a ford 9" i am putting in my ranger and i will be running 35s. i was wondering what was the best size gearing to use. ill be doing a lot of city driving so what is a good type of locker to put if any? also who makes good axles and strong gears.

when in doubt throttle it out


Krittro Campbell
What motor? 5 spd or auto? How much highway driving?

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Well-Known Member
I've got a97 with the 4.0 I had 4.56's in my 8.8 w/33's. Just swapped in a 9" w/ 4.71's cause I'll going to 35's soon.Even w/33's the 4.71 are only about 150-200 rpm higher.I got the 9" from performance differential in ontario,New ford housing,explorer brakes,detroit locker w/31 spline currie axles. Its 63" wide,maybe an inch or two too wide,but it matches the front.It doesn't stick out past the rear glass,just barely inside. My truck is a stick



Krittro Campbell
Jim at Performace Diff is who i always recommend...his work is second to NONE! He doesnt have any $8/hr guys assembling your diff...he does it all.

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Well-Known Member
I found that chrisman had the best prices when I got my gear and posi. I got 4.o ranger 33 tires and 4.56 gears.

midnight landscaper working overtime and I'm full throttle I'm full throttle tonight


Well-Known Member
Its easy, get the stock tire dimension from when the truck was factory new say 27" also you'll need the factory gear ratio say 4.30:1.

Take the 27" and divide by the 35" you wish to run and you get .77. The reciprocal (subtract from 1.0) is .23 or 23% bigger.

Now take the stock gearing 4.30 and divide by .77 and you get 5.58 and to double check your figures do it the same way, divide your current gear ratio by the new one 4.30/5.58 and you get .77 or 23%. This will maintain you existing RPM at a given speed.

Of course you're not going to get 5.58 gears so you need to take the gears that are close to what you want and do the divide thing again to see what the figure is. 4.30/5.29=.81 or 19%, since the percentage is lower the RPM will be lower at a given speed and the motor will have to work harder to accelerate.

Now something to keep in mind, if you raise up the truck you create a bigger brick to push through the air and you might want to go 5 or 10% bigger ratio to maintain performance at the cost of fuel mileage.

If you want to calculate the rpm at a given speed you can also take your MPH say 70mph at 3500 rpm and multiply the rpm by the bigger increase above 3500 x .77= 2695 with the bigger tires.

Gears are the cheapest horsepower ever bought, you can take a fuel efficient slug and make a rocket out of it if your willing to pay the price at the pump.

I just did a search and if your not interested in the math here's the various calculators your looking for <A target="_blank" HREF=></A>


VORRA Class 7


Well-Known Member
if you want to get really complicated, but also very accurate, check out Ramseys gear calculator that I attached

At baseball games they play organs, in motorsports they donate them.


New Tire
-------------- X Current Gear Ratio = Same ratio before you installed taller tires.
Old Tire

---------- X 3.55 = 4.01