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Project 240SX – Part 4 – Nismo 6-speed Transmission
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Project 240SX – Part 4 – Bolt-In Nismo Reinforced Six-speed Transmission
Nismo Coppermix Single Plate S15 Clutch KitNismo parts are high quality, properly documented, complete and install like OEM because they are, basically, OEM engineered. We reported in the first installment of Project 240SX about the Nismo Competition Parts clutch kit that we picked up from Tomei USA. The single plate Coppermix clutch is rated to hold 391 lb-ft of torque and engages lightly and easily. It’s also 1.4-lbs lighter than the factory SR20DET clutch. The Nismo Coppermix aluminum flywheel is 3.3-lbs lighter than stock for a reduction in rotating mass but the most important thing about our clutch kit is its S15 fitment.
The Nismo Coppermix kit includes the clutch, pressure plate, flywheel, throw-out bearing, new flywheel bolts, and pressure plate bolts - everything you’ll need to install, except for the alignment tool
The Nismo reinforced six-speed requires a switch to a S15 clutch assembly. Notice the depth on the aluminum flywheel. This sits out the clutch much further compared to stock and compensates for the six-speed’s input shaft location
The Nismo clutch kit fit without any problems. Those familiar with the S13/S14 240SX clutch will now notice how much farther the S15 Silvia unit sticks out
Our old Exedy clutch kit showed obvious signs of abuse and overheating. Just take a look at the rainbow on the backside of the flywheel
Nismo Reinforced Six-Speed TransmissionThe S15 Spec R picks up its speedometer signal electronically from the rear ABS sensor and a S15 six-speed transmission swap necessitates a swap to the rear S15 pumpkin and lots of custom wiring to get the S15 gauge cluster to work (the S13 and S14 gauge clusters will not read the S15 speedo signal). So, unless you’re truly dedicated or don’t care to know how fast you’re going down the street, a S15 six-speed transmission is not a direct bolt in option into any USDM 240SX.
Nismo offers the reinforced six-speed transmission with a multitude of kits to make it a direct drop-in into any S13, S14, or S15 equipped with a SR20DET or SR20DE engine. If you own a S13 or S14, you’ll need to swap over to a S15 clutch at the same time just like we did, on account of the difference in depth between transmission input shafts. The S15 flywheel, pressure plate and clutch will bolt on directly to any SR20DET engine.
The Nismo reinforced six-speed transmission kit from Tomei USA comes with the case pre-assembled and with Nismo labels for every single part. This includes the harnesses, bolts, transmission mount, shifter, and driveshaft
Barely visible from the outside is the speedometer drive gear in the Nismo six-speed transmission. With this feature, the Nismo unit becomes a direct bolt in swap. S15 Silvia Spec R trannies don’t have this gear and require a lot more work to fit
Compared to the SR20DET five-speed transmission, the Nismo gearbox is 3.8-lbs lighter despite having one more gear inside
We paid a visit to Steve Rodgers at SR Motorcars in Gardena, California and swapped out our tired five-speed transmission in less than half a day. Rodgers knows the S-chassis and SR20DET engine inside and out and made short work of the installation after lifting the transmission into place with a Herculean effort. We were pleasantly surprised to discover just how simple Nismo has made this six-speed swap. All parts are labeled and separately bagged and have perfect clearances. The included driveshaft was the perfect length and had zero balance or vibration issues. After we fired up the car, it was ready to go and the speedometer functioned perfectly. This is what you get with near OEM level engineering.
According to Nismo, the designed engine torque capacity of the five-speed and S15 Silvia Spec R six-speed is 217 lb-ft of torque and the capacity of the Nismo six-speed is 289 lb-ft of torque, thanks to gearing and gear diameter changes
Nismo GT L.S.D. ProWhen it comes to 240SXs, a limited-slip differential is a must. Look at it this way - when Project 240SX goes around a corner, its rear wheels travel in two different arcs and thus the two wheels are moving at different speeds. With an open differential, the same amount of torque is distributed to both wheels at all times and as you corner harder and one tire begins to lose traction, that tire will go up in smoke and continue to do so unless you ease off the gas. As the tire spins into dust, that wheel is exhibiting a much higher wheel speed than the wheel opposite of it. The problem with this is that the non-spinning wheel, the one with grip, will ultimately be fed the same low amount of torque that the spinning wheel is capable of holding.
The Nismo GT L.S.D. Pro kit includes everything you’ll need for installation including new OEM differential bearings, pumpkin cover gasket and bolts. Be sure to get more synthetic 80W90 oil for the fluid change after break-in
The Nismo LSD even comes with new and proper stub axles, which will eliminate any headaches about having the wrong parts. You will, however, have to be sure to get the correct fitment for your S13, depending on if it has five or six-bolt axles
Twenty clutch plates are used within the Nismo differential to ensure that the locking behavior of the LSD is smooth and predictable. We went with a 1.5-way unit for track and street use
For Project 240SX, we wanted a LSD that was responsive and provided a smooth, easy breakaway at the limit. We again contacted Tomei USA, this time for a Nismo clutch-type LSD, and they told us about the GT L.S.D. Pro. Clutch-type LSDs work by using springs that apply an “initial torque” to the clutch plates found within the LSD itself. As one wheel begins to spin more than the other, it locks the clutches together, transferring power to the opposite wheel. A higher initial torque value or tighter clutch pack will allow less speed differential between the wheels, locking the wheels together sooner. Drifters will often use a higher initial torque value than road racers as they actually want their cars to kick out soon after applying the gas during cornering.
Hidden within the Nismo GT L.S.D. Pro is the 19mm head to adjust the initial torque setting. It’s possible to leave the LSD on the Low setting for street and road course use and then turn it to High for a drift day. Just jack up the car and pop off the right axle stub, no need to drain
New differential bearings are highly recommended when swapping out LSDs and here Steve of SR Motorcars prepares to press ours onto the differential. Be sure you have the right equipment before attempting this job
The simplest way to tell your final drive gear ratio is to count the teeth or check the ring gear. 49/12 = 4.083 for a R200V S13/S14 SR20DET manual. S13/S14 SR20DET automatics came with 3.916
We filled the pumpkin with the included 80W90 synthetic Nismo Versuspeed LSD oil and then broke in the differential by driving two hours to Buttonwillow Raceway and then doing laps. Nismo suggests a break-in of 186-miles at no more than 37mph. We’ve done, uh, more than that and at an angry pace that’s a bit faster as well. After another 550-miles on the car, we’ve only experienced the slightest of clunking when the car is cold and warming up. But once up to temperature, there is nothing from the LSD but glorious throttle steering. Faster and more fun? Works for us.
Continue on to Project 240SX - Part 3 - Track Suspension >>>
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