| Axle Ratio | Final Drive |
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Final Drive Ratio Explained
The final drive ratio is the combined reduction from the engine to the drive wheels in a particular gear. It is the transmission gear ratio multiplied by the axle ratio, and it is the number that actually governs how the car feels in that gear. Because it stacks two ratios, even small changes to either one shift acceleration and cruising RPM noticeably.
Why It Changes Every Gear
Each transmission gear has its own ratio, so the final drive is different in every gear even though the axle ratio stays fixed. First gear gives the tallest final drive for launch, and top gear the shortest for relaxed highway cruising. That is why builders pick an axle ratio to suit how the whole gear spread lands.
Tuning With the Axle Ratio
Swapping the axle ratio shifts the final drive in every gear at once. A numerically higher axle ratio quickens acceleration and improves towing but raises cruising RPM and hurts economy; a lower one does the opposite. The axle table shows how the final drive moves as you step through common ratios.
Frequently Asked Questions
Is final drive the same as axle ratio?
Not quite. The axle ratio is just the differential. Final drive is the axle ratio multiplied by the transmission gear ratio, so it varies by gear.
Which gear should I use for cruising RPM?
Use your top gear ratio. Multiply it by the axle ratio for the highway final drive, then pair it with tire size to find engine RPM at speed.
Does a taller final drive mean faster?
Numerically taller (higher) means quicker acceleration but lower top speed and higher RPM. Lower means the reverse.