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4x4 Gear Ratios

How to select the right gear ratio for your 4x4?

Lets begin with looking at the big picture.

Just like a car a 4x4 has an engine and a transmission. In addition it has a transfer case moving pover front and rear.

Taking my own 4x4 as an example it has a transmission with the lowest gear of 2.47 and the 4Lo is 2.48. My differentials are 4.88. Multiplying these three ratios gives me the overall gear ratio or crawl ratio of 29.77 - a reasonably low number for a 4x4 with an automatic transmission.

When getting bigger tires for your 4x4 it is easiest to change the gear ratio in the differential.

Tire Size Calculation

When you plan on getting bigger tires you have to calculate a new gear ratio for your differentials. This is both for performance as well as fuel economy.

You begin with multipling your new tire size with your old gear ratio and dividing the result with the old tire size. This is a simple formula that gives a pretty accurate result. Continuing with the example I multiply 38 with 3.91 and divide the result with 30 giving me the number 4.95 where the closest awailable gear ratio is 4.88.

Differential Gear Ratio

The gear ratio most interesting to 4x4 truck owners is the ratio between the driveshaft and axels. It is controlled by the number of teeth in the ring vs. the pinion.

Lets look at these two perfectly rount gears. The smaller one is the driving gear and the larger the driven gear. If the smaller one has 10 teeth and the bigger one 20 the gear ratio between them are 20 to 10 or 2 to 1.

The differential works in the same way except the directions of the axles are at a 90° angle. So the pinion is an extension of the driveshaft and the ring is around the axles. In this case the pinion has 8 teeth and the ring 39 teeth. Dividing gives us the real ratio 4.875

Transfer Case and Transmission Gear Ratios

A list of the 4x4 gear ratios used in popular transfer cases and transmissions.

When you lift your 4x4 truck you consider your options for lowering the overall gear ratio. In addition to the ring and pinion gear ratio in the axles you may consider other options for your transfer case and transmission.

Please bookmark this page for later reference!

 

4x4 Gear Ratios

Transfer Case Gear Ratio

Dana 300 - std. 2.62
Dana 300 - 4:1 4.00
Dana/Spicer 18 2.46
Dana/Spicer 20 2.02
Borg Warner 1356 2.69
Toyota (67-74 3 speed) 2.31
NP 203 2.00
NP 207/208 2.61
NP 231 - std. 2.72
NP 231 - 4:1 2.72
NP 205 1.98
Atlas 2.0:1 2.00
Atlas 3.0:1 3.00
Atlas 3.8:1 3.80
Atlas 4.3:1 4.30
Atlas 5.0:1 5.00
Quatra-Trac 2.57

Transmission Gear Ratio

1st 2nd 3rd 4th 5th 6th Rev
Muncie SM 420 7.00 3.60 1.70 1.00 7.05
Muncie SM 465 6.55 3.58 1.57 1.00 6.09
Mazda 5-spd 3.40 2.20 1.50 1.00 .79
New Venture NV3500 4.02 2.32 1.40 1.00 .73 5.04
New Venture NV4500 5.61 3.04 1.67 1.00 .73 5.63
ZF S6-650 5.79 3.31 2.10 1.31 1.00 .76
Torqueflite 727 2.45 1.45 1.00
700R4 3.06 1.62 1.00 .70
4L80-E 3.10 1.48 1.00 .75
Allison 1000 3.10 1.81 1.41 1.00 .71 4.49
Aisin AX-5 3.93 2.33 1.45 1.00 0.85 4.74
Aisin AX-15 3.83 2.33 1.44 1.00 .79 4.22
Peugeot 3.39 2.33 1.44 1.00 .79
Borg-Warner SR-4 4.07 2.39 1.49 3.95
Borg-Warner T-4 4.03 2.37 1.50 1.00 3.76
Borg-Warner T-5 4.03 2.37 1.50 1.00 0.86 3.76
Borg-Warner T-18 4.02 2.41 1.41 1.00 4.73
Borg-Warner T-18a 6.32 3.09 1.69 1.00 7.44
Borg-Warner T-56 2.97 1.94 1.35 1.00 0.84 0.62 3.38
Borg-Warner T-86 2.80 1.69 1.00 3.80
Borg-Warner T-98 6.40 3.09 1.69 1.00
Borg-Warner T-150 2.99 1.75 1.00 3.17
Borg-Warner T-176 3.52 2.27 1.46 1.00 3.52
Borg-Warner T-177 3.82 2.29 1.46 1.00 3.82
Borg-Warner T-178 3.00 2.08 1.47 1.00 3.01
GM Powerglide 1.76 1.00 1.76
GM ST-300 1.76 1.00
GM TH350 2.52 1.52 1.00
GM TH400 2.48 1.48 1.00
GM TH200-4R 2.74 1.57 1.00 0.67 2.07
GM TH700-R4 3.06 1.62 1.00 0.70 2.29
GM 4L60 / 4L60-E 3.06 1.62 1.00 0.70
GM 4L80E / 4L80-E 2.48 1.48 1.00 0.75
Ford C4, C5 & C6 2.46 1.46 1.00
Ford E40D/4R100 2.71 1.538 1.00 0.712
Ford AOD 2.40 1.47 1.00 .67
Chrysler Torqueflite 727 2.45 1.45 1.00
Chrysler 904 2.70 1.54 1.00
Thrandur Arnthorsson

Thrandur is the chief-editor and owner of 4x4 Off Roads and an 4x4 off road enthusiast. Living in Iceland he loves to share the coolest 4x4 trucks and supporting more offroad freedom.
If you want to get YOUR 4x4 featured on 4x4OffRoads you can post your story here.

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