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Bryan Irons
SPEC Clutch
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Bryan Irons
SPEC Clutch
1. Our SPEC 3+ clutch kit came with everything from the pilot bearing to the throw-out bearing, and everything in between, including an alignment tool.
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Bryan Irons
SPEC Clutch
2. For the monstrous amount of torque we plan on unleashing, ARP hardware for the flywheel and clutch are a no-brainer. The bolts have a specific shoulder that slide into the flywheels countersunk holes. This ensures the twisting force of the flywheel is putting side load on the strongest part of the bolt, the shank, and not the threads. Also notice the tapered washers and the tapered edge that faces the bolt heads. This allows the radius under the bolt head to remain intact.
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Bryan Irons
SPEC Clutch
3. We pulled the original and pooched pilot bearing before the crank even went to the machine shop. There are plenty of methods and tools to do this job; we prefer the “hydraulic” method which involves packing grease behind the old bearing and hammering an alignment tool into the grease filled cavity to force it out.
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Bryan Irons
SPEC Clutch
4. Installing the new sintered bearing is a cinch with a bushing driver. Take your time and don’t go “Cro-Magnon man” and mushroom the ends pounding it home. If you’re on the frugal side of the spending line, a block of wood will suffice in deadening your ham fisted blows.
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Bryan Irons
SPEC Clutch
5. Place the included alignment tool unto the pilot bushing and degrease the flywheel, clutch plate and pressure plate before installing the bolts.
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Bryan Irons
SPEC Clutch
6. Turn the bolts in one turn at a time until you reach the factory specified torque. No need to gun them down and get the alignment tool crooked and jammed. It should slide out easily. Now time to enjoy an adult beverage before manhandling the 90 kg transmission into place while your buddies ignore your call for assistance.
Story & photos by Bryan Irons
Our green trail brute “Stinky Jeep” earned its handle early on in the life of a loyal 4x4 subject. The “Jeep” portion is self-explanatory; the “Stink” came from a mixture of automotive fluids and clutch linings endlessly escaping their homes while we sorted the rig out many moons ago. The worst was the smoked clutch, like the scent of burning varnish; it’s a smell you will never forget, no matter how much you try.
The primary cause was the rather tall gears in the axles and a transmission lacking a Granny Low gear. As a result, our flywheel had more burn marks then a Taliban hideout after an air strike. The thought of our rolling junk hemorrhaging oil all over a fancy clutch sandwiched between the transmission and motor just didn’t make sense at the time, so we kept the parts store “one size fits all” unit mashed in there.
With nearly four times the power the Jeep left the Toledo factory with some 30 years ago, our Merican Metal Menace 401 was not going to play nice with the rest of the drivetrain in Stinky Jeep. With all fresh seals and a manual stick behind the motor that could handle the force, not only was it time for a new clutch, it was REALLY time for a new clutch.
Unsure what direction to go, we laid out our criteria and called SPEC Clutches with the preconceived notion that they just would not understand what we were trying to do. As such, we spilt our guts;
- We needed a unit we could easily drive every day without developing pop-eye leg.
- It had to be able to handle the ridiculous power level we were transmitting.
- The clutch package had to mate up a Ford T-19 and an AMC engine.
- For proper off-roading agility, we had to be able to slip the clutch gently and not have it grab and break drivetrain parts.
- We’re magazine editors… budget does matter. A twin disc $1,500 unit was not going to work.
Then we waited to hear the Dr. Phil “you need to change your expectations” southern drawl answer… it never came. The voice on the other end politely informed us that a SPEC 3+ series system would fit all our criteria and a clutch disc, pressure plate, throw-out bearing, pilot bearing and alignment key could be boxed up and shipped to our door that day… “Uh, let me find a credit card…”
For some background on clutch selection; ceramic clutch discs have a reputation for extreme holding capabilities, but tendency to grab once warmed up. This is not ideal when trying to gently slip the clutch to crawl over obstacles and leads to broken parts and a lack of control. The clutch disc is typically a solid unit that allows greater feel, but with a lack of smooth engagement. Organic clutch discs are your more commonly found material and offer smooth engagement, long life and easy driving. But they are susceptible to harmful debris, and oils of any sort will hamper the clamping ability of the materials. They are also not the most reliable when it comes to high horsepower applications, but if you are driving… say, a 60 hp aluminum Suzuki (editor Stanley) this may not be an issue. SPEC’s complete 3+ kit has a special carbon semi metallic clutch disc capable of holding over 700 ft-lb, while still capable of being driven to work every day and modulated for crawling over tricky obstacles. The hub is spring loaded like a factory style clutch for smooth engagement and will tolerate some driver error.
No matter your choice of clutch, we always recommend replacing everything you can get your hands on while the rig is apart. This includes seals for the motor and transmission, throw-out bearing, pilot bushing/bearing, pressure plate and always resurface the flywheel. With everything at our door, it was time to assemble the clutch system, follow along as we make sure this is the last time we have to look inside this bellhousing for the next decade!