Now is a good time to begin...
Now is a good time to begin cleaning your rear end and parts in a solvent tank before moving on to the next step.
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.
Remove the 10 mounting bolts...
Remove the 10 mounting bolts (55 lb-ft) in a crisscross pattern to remove the ring gear. As a precautionary measure, we recommend using some thread-locking compound on each of the bolts when reassembling with the new gear set.
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 |
Here's a side-by-side view...
Here's a side-by-side view of the new ring gear set on the left and the factory S2K unit on the left. To the naked eye both gear sets look similar but upon counting the gear pitch, we found the Kia unit has 43 teeth and the S2K has 41.
The pinion on the Kia was...
The pinion on the Kia was visibly smaller when sized up to the S2K unit. The Kia setup, measured with a dial caliper, sized up at 2 6/8 inches with a nine-tooth count and the S2K measured 2 7/8 inches with a 10-tooth count.
Using our bearing remover,...
Using our bearing remover, we installed the tapered roller bearing onto the pinion gear. Be sure to install the correct sized thrust washer, which should be measured and toleranced, as only the installer will know when he installs the gear set. Honda offers a shim kit that comes with an assortment of thrust washers to speed up the process (more on the thrust washer as we finalize the install). Tighten the locknut on the pinion drive while applying grease to the tapered roller bearing. Install the drive pinion and pinion spacer into the differential housing and tap it into place using a mallet. Install the oil seal then tighten down the locknut (14 lb-ft). Rotate the drive pinion a few times to ensure proper tapered roller bearing contact. If the drive pinion turning torque is within specs (see service manual) then tighten down to 210 lb-ft of torque.
Install the LSD assembly,...
Install the LSD assembly, bearing outer races and adjustment screws onto the differential carrier housing before installing and aligning the bearing caps marked from earlier. Hand tighten the four cap bolts.
The most crucial step when...
The most crucial step when installing the new differential is to measure backlash on the ring gear using a dial gauge indicator. Measure four points on the ring gear within 90 degrees apart to get a reading in tolerances. The backlash is within standard if at one point of measurement, the ring gear backlash is within the standard, minimum measurement of 0.05mm or above and the difference between the maximum and minimum measurements do not exceed 0.07mm. Use a pair of needle-nose pliers to adjust the screws and tighten the endcaps to 33 lb-ft when complete.
Backlash: (as per Honda Specifications)
Standard: 0.09mm-0.11mm (0.0035-0.0043 in.)
Minimum: 0.05mm (0.0020 in.)
Difference range: 0.07mm (0.0028 in.)
Rotate the pinion a full revolution...
Rotate the pinion a full revolution forward and backward to inspect the contact pattern between the ring and pinion, ensuring no binding or excessive gap is present. If the tooth contact between the ring and pinion is showing toe contact (placement near the edges) you'll need to install a thinner trust washer. If the setup is displaying the exact opposite, known as heel contact, then replace the original washer with a thicker unit. After completion, install the lock plates and torque them down to 16 lb-ft before reinstalling the differential case assembly.
While Honda doesn't state...
While Honda doesn't state the need to use silicone to seal up the pumpkin, we opted to use some sealant to ensure our rear differential doesn't promote unwanted leaks.
Tighten the 10 mounting bolts...
Tighten the 10 mounting bolts in a crisscross pattern (17 lb-ft) and reinstall both output shafts.