Only the speedometer ring gear needed to be transferred from our stock NSX LSD (right) to
When it comes to differentials, OS Giken makes the Cadillac of them all. Well, maybe that's an insult nowadays-call it the Ferrari of performance drivetrain components. The OS Super Lock 1.5-way LSD for the NSX is a clutch type unit with a total of 24 clutch plates (12 on each side). The idea behind having so many plates is to provide enough friction surfaces to have a differential that can truly provide lock up 100 percent under load while being able to slip enough for smooth low-speed operation. Each diff is built with heat-treated internal components, raw-forged gears and precision-machined plates that eliminate the vomit-inducing figure-8 break-in required by most other clutch-type LSDs.
Another patented innovation found only in the OS Super Lock LSD is the small preload springs used in the main pressure ring. This Lock Timing Technology uses these springs to control the release and expansion of the pressure ring in the center of the diff, which in turn controls when and how much the clutch plates engage. OS can custom tune each LSD's clutch engagement timing as well as torque preload. These fine-tuning tricks are what allow the OS Super Lock LSD to provide smoother operation, faster locking, less turn in understeer and even better wet/snow traction.
The engineers at OS determined that the a 1.5-way LSD was the best for FF and MR applications and only offer these off-the-shelf with pre-tuned initial torque and lock progression settings. More or less aggressive units can be special ordered as well as custom set up but factory standard settings are usually best for most users, even in racing.
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All the gears from the stock countershaft (top) need to be transferred to the new OS count
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With the new gears installed, we could assemble the transmission with the new inputshaft,
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A less expensive alternative to replacing all the synchros (brass), hubs and sliders (silv
Gears
Part of the option for our OS Super Lock LSD was their 4.44:1 final drive ratio. The LSD comes with the 4.44 ratio ring gear already mounted, a new countershaft with the matching pinion gear, as well as a new transmission oil pump gear with the same gear teeth that's also driven off the new ring gear. The only hardware that needs to be transferred from the stock NSX LSD is the speedometer ring gear. Even with new bearings, the installation of the new differential is a straightforward drop-in deal. The original differential bearing shims didn't need to be changed on account of OS' super-tight machining tolerances. With the new shorter final drive, we can now keep the engine at reasonably higher speeds for more power even at street speeds. This will give us more acceleration, response and actual torque at the wheel both from the higher drive ratio and the higher-rpm power with the trade-off of more time spent shifting.
While the transmission was apart and the countershaft replaced (since the pinion gear is part of the countershaft), we opted to also replace the stock USM gears with JDM spec gears which feature a more evenly spaced ratio. Even spacing between the gears allows for the engine rpm to drop right back to just before the stock VTEC engagement point after shifting from the 8000-rpm redline. ScienceofSpeed imports these OEM Japanese gears, which are a direct bolt-on into the U.S.-spec transmission. Some of the gears are directly forged onto the input shaft itself, so the kit comes with a new input shaft and the appropriate second through fourth gears and countershaft gears. Although the gears are different in diameter, the synchros are identical for each gear, so we also ordered new U.S.-spec bearings, brass synchronizer rings, gear selection hubs and sliders as well as new synchro springs for the entire transmission.