Rolling away from the Port of Tacoma we could tell straight away that our R32 Skyline’s clutch was on borrowed time. It had a vague engagement point and unsure authority when going about its business. It felt old. The car was driven sparingly, a handful of 80-mile trips and our bi-weekly 12-mile loop to keep the fluids flowing. Then, about a year and a half after taking delivery, as it was pulling out an uphill driveway in route to its new home garage there was a horrible squeal, a freewheeling sensation, and the undeniable smell of clutch death. Godzilla was frozen in its tracks.
We had to hustle and get the R32 back up and running because we intend to install an AEM Infinity ECU and, eventually, boost up the party with a pair of bolt-on Garrett turbos. With a goal of 450 to 500 wheel horsepower we knew we needed something next level. After burning up the information super highway we contacted Spec Clutches of Bessemer, Alabama.
R32 Skyline Clutch Spotters Guide
Early R32 Skylines feature a push style clutch while in early 1993 Nissan moved to pull-type actuation. Those in the transition zone can look at the right side of the transmission and if the clutch slave cylinder engages the clutch fork from in front of the fork it’s a push type. If the clutch actuation assembly is mounted behind the fork it’s a pull style. We were surprised how many clutches were listed on the net as R32 clutches with no reference to actuation type.
Pick Your Disc
The biggest decision was which clutch design to go with; a conventional single disc, a twin-plate, or a multi-plate. But what’s the diff? The co-owner of Spec Clutch, David Norton, was quick to chime in, “A multi-disc clutch is called for when the capacity of a single becomes insufficient or when drivability of a sufficient single-disc design has deteriorated to the point that the car is no longer fun to drive. Multiple disc set-ups can hold more torque in the same amount of bell housing space than their original equipment single- or twin-disc counterparts. More discs mean more surface area, and more surface area not only provides a higher capacity, but also adds progressiveness to the engagement and, thus, more streetable performance. A twin-plate unit will have one more friction disc and an extra surface, termed a ‘floater’ or ‘center plate.’”
A Material World
Going twin was the perfect fit as it would deliver the power holding capabilities we’re looking for and we wouldn’t need Herculean calf muscles to work the pedal. Spec Clutches has two lines of twin-discs, the Mini Twin and Super Twin. “The Mini Twin is simply our small diameter (184mm) twin, triple, and carbon/carbon line,” says Norton. “These units are strapless and made for small bell housing applications and any application that benefits from low inertia. The Super Twin is our larger diameter twin with a focus on drivability and even more capacity. The Super Twin units range from 215mm to 305mm in diameter.”
The Spec pressure plate (above) is a solidly built billet piece. Clutch discs (below) come in many designs and use a wide variety of materials here we see a six puck and a solid disc.
We were all-in for a Super Twin. Once that determination was made, the next fork in the road was clutch disc material and surface configuration. This is where the trim comes in. Spec uses SS, P, ST, and E to establish its trim hierarchy. The difference between trims boils down to the materials in the clutch disc. Norton says, “the first step is always to narrow down the stage choices based on your torque output. Sprung versus rigid does not matter much in terms of drivability, as the larger diameter of the Super Twin doubles the effective surface area, adding quite a bit of progressiveness to clutch engagement. So unlike a single-disc set-up, it is very difficult to tell the difference between a sprung versus rigid configuration. The E-Trim, however, only comes rigid. The SS-Trim is an organic or a puck/segmented hybrid like our Stage 2+ single disc. The P-Trim is a 3-, 4-, or 6-puck like our Stage 3 or Stage 4 single discs. The ST-Trim is a full-faced carbon graphite, semi-metallic design like our Stage 3+ single. The E-Trim is hardcore sintered iron, like our Stage 5 single disc.” We went with an SS trim.
Torque Capacity (lb-ft)
The install was handled by AW Automotive in Auburn, Washington. The “AW” stands for All Wheel and the shop specializes in Evos, Subaru WRXs, and the occasional Skyline GT-R. Lead technician Logan Coutts would be spearheading the project. He’s been at AW for about two years and says clutches are the most popular job and he’s done around 200 of them. “I know Spec Clutches very well. I have friends who run them on their 1,000-horse drift cars. The twin is going to be a nice setup for the GT-R because it’s not overly aggressive but it’s still going to be beefy. I mean this clutch is probably good for 650 to 700 horsepower.”
With the battery disconnected for safety and the shifter unbolted from inside the car, the two bolts holding on the clutch slave cylinder are removed and the slave cylinder is freed from the clutch fork. A pull-style clutch would have its slave cylinder mounted on the other side of the clutch fork where it would pull on the fork to disengage the clutch.
The front driveshaft is unbolted from its forward most attachment point. Coutts marks one of the bolt locations to ensure the shaft is replaced just as it was removed to retain the OE-spec balance of the driveline.
The exhaust bracket is taken off and the top starter bolt is removed from the topside under the hood. The transmission and transfer case are drained and the rear driveshaft is loosened (pictured).
After unplugging electrical connector plugs for reverse lights and neutral position switch on top of the transmission, the vehicle speed sensor is unscrewed. Then the gearbox is supported and the transmission crossmember is removed. Using a long extension, the upper bell housing bolts are then removed.
At this point the transmission is ready to be wrestled. The maneuver consists of a raise, a twist, and a hefty pull to get the gearbox free of the input spindle.
The pressure plate and disc were removed and we watched a friction material snow storm fall to the shop floor. The stocker was certainly spent. The old flywheel was removed and it was time to put humpty back together again.
Job One was to installed the new Spec billet flywheel using new bolts provide in the Spec kit. “New flywheel bolts are an extra as many kits expect you to use the originals,”said Coutts, who torqued the fresh flywheel bolts to the 140 to 152 newton meters demanded by the Skyline GT-R service manual. Coutts used a 150 nm target which translates to 113 lb-ft… “Sometimes you have to go JDM on the specs,” he quipped.
“The alignment tool is especially critical in twin-plate and more so in multi-plate installs,” says Coutts, “because you have more moving parts, clutch discs and friction plates, and there are a lot of fine adjustments that must be made.” The discs and friction plates are arranged in the proper order. The discs are marked Trans Side and Flywheel Side so they can be installed in the correctly and facing the right direction.
The inner clutch assembly is lined up with the Spec pressure plate so that the yellow alignment marks on the pressure plate and friction plate line up.
Using the alignment tool to keep everyone happy and in line, Coutts finger tightened the pressure plate bolts to secure the clutch. Coutts recommends a red thread locker for these bolts.
This is followed up with a impact wrench and a torque wrench that tightens the flywheel bolts to Spec specs, in this case 25 to 30 lb-ft.
A fresh release or throw-out bearing, provided with the kit, is pressed into place. The bearing is mounted to the clutch fork with a weird cotter pin clip.
The release bearing and clutch fork are reinstalled in the transmission.
After some repeated coaxing it was decided that added thickness of the new clutch assembly meant the transmission needed to be positioned farther back to get the input shaft to align and slide into the clutch splines. As a result the rear driveshaft was removed.
The push to get the transmission back in place was a showdown. It was epic… not a Samson versus Goliath… more like Samson and Goliath versus the Godzilla transmission. The forces of good prevailed. Redline Lightweight Shockproof gear oil was added and the GT-R was ready to roll.
Breaking In The Beast
Breaking in the clutch only required the resistance to unleash the boost. “In general, break-in procedures entail normal usage to seat new surfaces,” says Norton. “Normal usage does not mean babying the clutch, but simply refraining from burnouts and high-rpm speed-shifting until the clutch is ready to hold the torque. Premature aggressive driving can take wear life from the clutch, produce heat-related issues that can affect drivability, or even permanently damage the clutch and surfaces. Any clutch company that says their unit does not require break-in is making a marketing statement. The reality is, just like brake pads, seating always benefits performance and wear life, and can prevent the possibility of damage due to ‘too much too soon’ power application. Most of our stages will work just fine without break-in, but we would be selling the experience short by not expressing the benefits of seating.”
On The Road With Godzilla
Maybe I was in fear of some of the ‘on-off’ switch racing clutches I have driven in the past, but I was really astonished at both the engagement and easy pedal of this set-up. There was no catch, no shuddering, just a seamless moment of inertia, a smooth transition to motion, and carefree acceleration. Pedal engagement was right off the floorboard but even that didn’t trip me up. Forget multi-plate madness of race clutches, the Spec twin-plate was more civil than the single-plate I daily drive in my Evo IX. We’re off to a great start.
Zilla’a New Shoes
The first mod we made with Project Godzilla was upgrading the wheels and tires. The car had stock 16-inch GT-R wheels that were in pristine condition but the tires were as bald as ESPN’s Scott Van Pelt. We had a plan before the GT-R was even loaded on the boat… Advan Racing.
The dream car deserved some dream wheels. It was going to be Advan or Volk Racing... either way Mackin Industries was in our future. Center caps for the RZIIs come in three depths. They are expensive so know your axle stubs. The R32 uses the middle of the three offerings.
Mackin Industries is the official importer of Advan, Volk Racing, and a number of notorious JDM companies. We went for a plus two upgrade and installed 18-inch RZIIs. The RZIIs are finished in Advan’s Indigo Blue powdercoat and the R32 is running 18×9 +25 in front and 18×10 +25 in the rear. The fitment in front required trimming the inner fender line toward the nose of the car. The Advans are wrapped with Falken Azenis FK950 tires which provide outstanding grip and excellent rain performance, which is key since Zilla is roaming free in the great northwest.
The clutch is a critical link between the engine and transmission but it also links you with your car, impacting the driving experience and ensuring all your tuning makes it to the road… and it’s a costly endeavor so care and forethought should be used when contemplating a replacement or upgrade. In our case, peace of mind was a big factor as well and we have thought ahead to the coming mods and selected a unit that perfectly blends power holding and ease of engagement.
Before we leave you, here’s some bonus information for anyone interested in learning the ins and outs of importing a 25-year exempt vehicle. We ran a 3 part series called, “Buying Godzilla.” Check it out and happy hunting!