Divide ring-gear teeth by pinion teeth to get the axle ratio in x.xx : 1 format. Confirm 3.73 vs 4.10 before you shop gears — free, private, in-browser.
Count teeth on the large ring gear (typically 10–80).
Count teeth on the pinion (typically 5–30).
3.73
Numeric ratio
3.73 : 1
Axle ratio
Common references: ~2.73 highway-biased, ~3.73 balanced daily driving, 4.10+ for towing or low-speed torque.
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Count the teeth on the ring (crown) gear and the pinion. Ratio is ring ÷ pinion, shown as x.xx : 1 (for example 41 / 11 = 3.73 : 1). That is the axle (differential) ratio stamped on many housings — not transmission first gear, not crawl ratio, and not an “effective” ratio that folds in tire diameter.
Ring teeth 10–80 and pinion 5–30 cover common 3.08, 3.42, 3.73, 4.10, and 4.56 cuts. If the displayed ratio is not a catalog number, recount the teeth; a missed tooth on the pinion throws the second decimal off. Tags on the pumpkin are easier when the cover is still on.
Engine RPM at a given speed needs this ratio plus tire diameter and the transmission gear you are in — that is RPM at Speed. Off-road crawl is first × transfer-case low × this axle ratio. This page stays the simple division so you can confirm a 3.73 versus a 4.10 before you shop gears.
No VIN and no upload. Tooth counts stay in the tab. Close the page and they are gone immediately. This does not read a scan tool or a bill of materials from a dealer. Nothing is stored on a server.
The large gear in the axle. Mark one tooth and rotate until you return. Valid range in the tool is 10–80.
The small gear on the pinion shaft. Range is 5–30. Do not count the ring again by mistake.
Ring ÷ pinion, two decimals. Compare to the door sticker, a tag on the housing, or a parts catalog.
Those tools take this number as an input along with tires or transfer-case low. This page will not multiply them for you.
Straight answers on privacy, limits, and how the workspace behaves.
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