The first and most obvious would be losing top end speed but, on a positive note, improving acceleration off the line. The 4.77-ratio setup offers improved acceleration only when you're in the same gear as someone with higher gears. A prime example would be someone who drove in Fifth gear before would likely now be in Sixth gear now because of the 4.77 final drive. Off the line in First gear, the 4.77s will be quicker but as speed increases, the torque advantage decreases since you find yourself revving up in a higher gear. For n/a powered S2K owners planning on tracking their cars, the 4.77 ratio offers more torque, thus creating less of an issue at a lower rpm, especially on a technical course with more turns-like the Streets of Willow raceway in Rosamond, Calif. On courses that have longer straights, such as Big Willow, the 4.77-ratio setup is known to top out at 140 to 145 mph. For the novice driver, reaching those speeds would be a rarity but for the more advanced level, the limiting speeds might hamper your times going through the long sweeper through turn 8. One good advantage to owning a S2K geared on a set of 4.77s is being able to use Sixth gear as you shift through the turns-making your shift points and entry/exit speeds coming out of the turns more usable in terms of power.

As with any final drive modification, swapping out your final drive will send an incorrect signal to your speedometer. To remedy this problem, aftermarket speedometer recalibrators, such as the Yellow Jacket, can be used to recalibrate for the new final drive setup in your S2K. Units such as these are purchased over the Internet for $50 complete with instructions and wire harness. Other alternative systems include a slick unit known as the Yellow Box, which uses a series of dipswitches to recalibrate your vehicle and also has the added ability to convert from kph to mph.

So what's the most ideal gear ratio for your vehicle? Determining your final drive ratio will depend on whether you're running on forced induction or naturally aspirated. We've come across a number of supercharged S2K owners swapping out their factory differentials for a more favorable 4.44 final drive while the more hardcore road race individuals opt out for the 4.65 to 4.77 final drive setup. Whichever route you decide on following, always consult a Honda Specialist or certified tech before attempting to tackle this job on your own because honestly, driving at 9,000 rpm in Sixth gear doing 50 mph isn't exactly much of a thrill ride.

Be sure to replace the oil filler and drain plugs with new sets of washers before reinstalling the pumpkin back onto your S2K. Honda recommends using Hypoid gear oil GL5 or GL6 (viscosity No. 90). With your new ring and pinion setup, pay special attention during the break-in procedure and refrain from performing any hard launches or spirited runs for at least 500 miles at which time the old fluid should be replaced.

Vehicle Year/Model Final Drive
'94-'02 Kia Sportage 4x4 (front axle) 4.778:1
'99+ NZ market Kia Sportage 4x4 (front axle) 4.625:1
'94-'97 Miata 4.10
'99+ Miata five-speed (4.10:1 on automatic starting in 2000) 4.30
'87-'88 Mazda 4x4 truck (front axle) and Kia NZ Sportage optional 4.44
Mazda RX-8 4.44
'79-'85 12a RX-7 and ('99+ six-speed Miata) 3.909
'79-'82 RWD 626 five-speed ('01+ Australian six-speed) 3.636:1
Kia Sportage aftermarket gears are available 4.875:1, 5.125:1, 5.38:1
SOURCE
Signal Auto USA
1719 Abalone Ave. #401
Torrance
CA  90501
Yellow Jacket Speedometer Fix
Yellow Box Speedo Recalibrator