What gear ratio for 35 inch tires?

The catalogue stops just short this time

4.13:1 is what the arithmetic returns. 4.10:1 is what exists as a ring-and-pinion set. Unlike the smaller steps, where the available ratio overshoots the requirement slightly, a 35-inch swap from a 3.73 axle lands above the nearest rung, so buying the closest set leaves a fraction of the diameter change uncorrected. Whether that residue is worth chasing to the next ratio up is a decision about the vehicle, not about the geometry.

The same swap from other starting ratios

• From 3.55:1 the requirement is 3.93:1 and 3.91:1 is available — again slightly under.
• From 4.10:1 the requirement is 4.54:1 and 4.56:1 is available — this one overshoots.

The pattern is not a rule; it is what happens when a fixed ladder of manufactured ratios meets a continuous multiplier. The multiplier here is large: 35x12.50R17 is 10.74% bigger in diameter than 265/70R17, which is nearly two and a half times the increase a 33 represents.

What the engine sees if nothing is changed

3.37:1 is what the effective final drive becomes, down from 3.73:1. That is not a figure any part on the truck is stamped with — it is the ratio the engine behaves as though it has, because the tire is doing part of the gearing. At 70 mph through an assumed 0.84 overdrive it is the difference between 2,333 rpm on the original tire and 2,106 rpm on the 35. The 0.84 is a plausible ratio, not a measurement from any particular transmission.

Work it with your own numbers

Starting size matters more than anything else here, and 265/70R17 is only one of several plausible origins. The calculator with this case loaded takes a different tire, axle or speed and returns both the exact requirement and the nearest set on the shelf, gear by gear. The axle ratio basics page covers what the ratio is measuring in the first place.