⚙ Gear Ratio Calculator

Your engine's power gets multiplied on its way to the tires by a stack of gear reductions. Each one multiplies the one before it. More total reduction means more torque and slower, more controlled wheel speed for crawling over obstacles — at the cost of higher engine RPM on the highway.

There are three pieces of reduction on a normal rig (four if you run portals):

• Transmission (1st gear) — the first multiplication. A manual's 1st gear is usually deeper than an auto's. Only 1st gear matters for your crawl ratio.
• Transfer case (low range) — the extra multiplication you get in 4-Lo only. It's 1:1 in 2WD and 4-Hi (no reduction). A Rubicon's Rock-Trac is a deep 4:1; most others are around 2.72:1.
• Axle ratio (your diffs) — the ring & pinion gears inside each axle, like 3.73 or 4.56. A bigger number is more reduction. This is the part you "re-gear."
• Portals (only if equipped) — a final gear reduction right at the wheel hub. Adds reduction (and lift) without going to a bigger tire.

Multiply all of them together in 4-Lo, 1st gear and you get your crawl ratio — the single headline number for how slow and controlled you can creep. Roughly: ~40–50:1 is mild, 70:1 is good, 100:1+ is serious rock-crawling.

Bigger tires work against all of this. A taller tire effectively undoes some of your gearing — the rig feels sluggish and your crawl ratio drops. Re-gearing the axles (or adding portals) brings the feel back.

What this tool does: fill in your rig on the left, then on the right change only what you're upgrading — bigger tires, new axle gears, portals, a transfer-case swap. It shows the re-gear you'd need to restore your stock feel, and how your crawl ratio and highway RPM change. Tap the ⓘ next to any field or result for a one-line explanation.