|You can see the diff set up as a 1.5 way in this picture. The two halves of the differential gear carrier drive either axle. Inside them are the pinion gears also known as spider gears. When the axles try to turn independently the side gears put a torque on the pinion gears and cause the pinion shaft to try to turn. It wedges in this diamond shape hole in the gear carrier forcing the halves apart. This in turn puts a clamp load on the clutch plates. Because of the diamond and the cams shape, this gives full lock in the drive direction and half lock in the coast direction.|
While we had everything apart, we changed the gear oil with Royal Purple’s Synchromax high performance synthetic manual transmission fluid. Synchromax is formulated to improve shifting and to reduce gear noise, both items where the Nissan transmission has issues. It is also designed for optimum lubrication and wear resistance while being compatible with synchros. Royal Purple’s lubes form a bond to metal parts which prevents metal to metal contact. From the smell we think this means that the oil has a high EP additive content as it reeks way more than standard gear oil!
|In this shot the diff is set up as a one way. The cross shaft can only wedge the housings apart under drive load because the window is shaped like a triangle instead of a diamond.|
After installing the clutch and flywheel, we were amazed with the difference. The car shifted easily, heel and toe rev matching was a snap and the throttle response was a night and day difference, enough to put a smile on your face. Believe us; driving any car with a 29 lb flywheel is not fun. The clutch was as light and easy to drive as a stock clutch as well. The only negative is a slight rattling noise from the transmission. We will gladly take that in exchange for all the performance.
|Here are the pinion shafts or cross shaft with the pinion gears. You can see the cam shapes ground into the ends of the shaft. The Nismo diff has 4 pinion gears vs the stock two gears. This makes the diff a lot stronger.|
The next issue to be addressed was the installation of a limited slip differential. We considered many different diffs but ended up with a Nismo GT LSD due to its ease in adjusting the preload on the clutch pack and the initial break away torque.
|Mike Kojima fiddles with the clutch preload device built into the cross shaft assembly. This is a cool feature allowing easy adjustment of the initial breakaway torque for the differential.|