Axle Gear Ratio & Tire size change
conversion equation.
There are two
equations for figuring this out.
Equation or Method #1
New Tire Size (in inches) / Old Tire Size
(in inches) * Old Gear Ratio = New approximate ratio
35" / 33" = 1.0606 * 3.73 = 3.9560
37" / 33" = 1.1212 * 3.73 = 4.1821
Equation or Method
#2
New Tire Size (in inches) * Old Ratio /
Old Tire Size (in inches) = New Ratio
35" * 3.73 = 130.55 / 33" = 3.9560
37" * 3.73 = 138.01 / 33" = 4.1821
Both methods
produce the same result. If you are going to use one,
try and stick with it for your own personal consistency.
Refer to axle gear
choices and select closest ratio to make the vehicle
perform as close as possible to factory performance.
It is always
considered acceptable to go to deeper gears (numerically
higher) to gain more torque for crawling.
For the above
factors, going from 33's to 37's on a 2021 Jeep Wrangler
with Dana 44 AdvanTEK axles, the closest gear choice
would be 4.10. However, choosing 4.56 would be better to
give better gearing for future tire sizes up to 39" of
40"
Backlash 0.005 -
0.008
Pinion rolling
torque 15 - 30 inch pounds
Carrier Split on
Dana 30, 35, 44 is between 3.55 and 3.73
Meaning 3.73 and
lower gears will fit the same carrier. 3.55 or higher
gears will fit the same carrier.
This is important to know if you are going from a 3.55
to a 4.10, you'll need to get a carrier that fits the
lower gear sets.
