Goto Cavwo to know more.
FOR THE control freaks among us who like to select our own gears rather than let a computer do the thinking, there is one extremely important driveline component that needs to be treated with a great deal of respect and mechanical sympathy: the clutch.
Your vehicle’s clutch not only allows for engagement (and disengagement) between the engine and the gearbox, but it also dampens engine pulses to provide a smooth and consistent power delivery throughout the driveline.
If your vehicle’s OE (original equipment) clutch starts slipping or wears out prematurely, chances are you’re not treating it right or it’s simply not up to the job you’ve assigned to it.
In most cases (although, not always), vehicle manufacturers equip four-wheel drives with a clutch that’s adequate for said vehicle’s intended function, such as day-to-day driving, some off-road driving and some towing.
But manufacturers rarely take into account that off-roading enthusiasts usually take things to the next level: fitting bigger tyres, carrying accessories and gear, chipping the engine and fitting an exhaust, and dragging around a trailer that’s within a few grams of maximum stated towing capacity.
Do any of the above and you’ll soon find your vehicle’s standard clutch is left wanting, and whether it’s slipping, smelling or squeaking, it’ll need to be replaced before it fails completely. Rather than source another OE clutch, you’ll need to fit a heavy-duty aftermarket unit to cope with the additional demands that are a by-product of heavy loads, more torque or -towing.
AFTERMARKET ALTERNATIVE
ADELAIDE-BASED company Australian Clutch Services (ACS) has been supplying clutch kits and components for more than 25 years, and it offers a wide range of aftermarket heavy-duty clutch kits to suit most four-wheel drive vehicles on the market, under the Xtreme Outback banner.
“There are several advantages of fitting a heavy-duty aftermarket clutch over an OEM clutch,” said Stewart Furze, mechanical engineer at ACS. “In 4x4 applications – where you may be modifying the vehicle, you may be increasing power, you may be adding a lot of extra weight or towing – most of those users are going to be using the engine to its peak performance a lot of the time.
For example, when you’re towing, you’re going to be using the peak torque of the engine a lot more than you would be if you were just driving the kids to school. So, in those situations, that’s when the OE clutch may not last as long as you would expect.”
In those situations you’re likely to experience an accelerated rate of wear and the clutch will begin to slip. “A good example is the VDJ79 [Land Cruiser]. As soon as owners chip or tune them, the factory clutch just doesn’t hold the extra torque… so it’ll just slip straight away. In other instances, owners might just see an accelerated rate of wear to the point where it starts to slip after a couple of thousand kilometres after doing modifications.”
So why can’t an OE clutch cope with the demands of increased torque output or heavier loads?
“Generally it’s a lack of clamping force,” he said. “It’s also the extra heat that’s generated, which will accelerate wear. Any excessive heat, or harder engagement, or even riding a clutch because you’ve got more weight, that all generates heat, which will accelerate how quickly the clutch will wear.
“And if it starts to slip, that means that basically the clutch is either completely worn or it just does not have the clamp load required to carry the torque.”
CLUTCH DEVELOPMENT
AUSTRALIAN Clutch Services has an in-house R&D facility that provides it with the resources to analyse new friction materials and evaluate spring rates to obtain the optimal combination of performance, noise suppression and durability. When ACS sets about developing a range of heavy-duty clutch kits to suit a specific vehicle, its engineers first examine the specifications of the OE clutch.
“Our first port of call is making sure we know exactly what’s supplied by the factory,” said Stewart. “So we have a look at the specifications… to ascertain exactly what it will have. For example, 800kg of clamping force.
“As a general guide, most of our first stage [heavy-duty] kits offer around a 20 to 30 per cent increase in clamping force. So that’s our first goal: how can we achieve a 20 to 30 per cent increase in clamping force? The majority of our customers are only going to go for that first level of modification.”
Despite this increase in clamping force – designed to handle the extra torque produced by a modified engine and the additional stresses imposed on the driveline by heavy towing or extreme off-roading – ACS strives to retain drivability by ensuring pedal effort is not excessive, as well as ensuring the clutch has a nice, progressive feel.
“We try to optimise the operation effort,” Stewart continued. “We try to keep it as close to factory as possible. We also look at different friction materials and flywheel options. A lot of 4x4s have dual-mass flywheels, and in order to create heavy-duty options we need to create a single-mass flywheel conversion at the same time.
“Dual-mass flywheels are put into vehicles for a few reasons,” he said. “The main reason is noise suppression, and the other key one is driveability. More and more, the manufacturers are being pushed to offer smoother, quieter, more efficient cars that pretty much anyone can get into and drive without stalling them.
“A dual-mass flywheel does a very good job of softening up all of those factors… but as soon as you start to modify a vehicle, in ways that 4x4 owners do, that’s one of the components that doesn’t tend to last with extra power and extra towing.
“So every time we look at a single-mass flywheel conversion for any vehicle, we have to look at all of the parameters: the type of engine, the mass of the OE flywheel and pressure plate, and assembly, and we try to match that, because the mass of those components plays a significant part in noise suppression. But probably one of the key factors is the actual friction disc that we supply.
“We always try to have an idle rate, wide angle damper disc. That’s the best way of absorbing the noise and vibration that you get from the engine and transmission, which would normally be absorbed by the dual-mass flywheel,” Stewart explained.
“With any modification, whether it’s a suspension lift, whether it’s big tyres, whether it’s adding racks and bullbars and things like that, there’s always going to be something to counteract that modification...
“So if you’re fitting bigger tyres that have a mud pattern, they’re going to be noisy; if you’re lifting the car then it’s potentially not going to be as stable or smooth as it was from factory... So there’s always a compromise.
“And with clutches, if you’re adding a heavy-duty clutch, sometimes that compromise is as simple as a 10 per cent increase in pedal effort, and with a single-mass flywheel conversion sometimes that’s a small increase in NVH (noise, vibration and harshness) that can come through the cabin.
“But, generally, we always try to design the clutch in such a way that most people will hardly even notice a noise increase.”
CLUTCHES FOR COURSES
ACS OFFERS a variety of heavy-duty clutch kits to suit different applications, from those who drive unmodified vehicles through to those who want to go off-road racing.
“In four-wheel drive, we have several different levels depending on vehicle modifications and the type of use that the vehicle sees,” explained Stewart. “We cater for everything, from a person who might have a Nissan Navara or something similar and he’s a tradie who tows every day, to someone who’s actually going to go rock crawling.
“Generally, the first stage is just an increase in clamping force, with an original-style organic friction disc, and is something that will drive very similar to a stock clutch.
“The second stage is what we call an extra heavy-duty. So it’s a second increase in pressure plate camping force, still with an organic disc for drivability but a little more increase in pedal effort.
“And then you jump into the ceramic friction material. We have what we call a cushioned ceramic disc that still provides a small amount of drivability, but it can have a small increase in shudder and a small amount of pedal effort increase...
“Or we go straight to a button disc, which is normally something that guys who are doing a Dakar-type rally would be using,” Stewart said. A button disc is essentially a friction disc, which still has a sprung centre, but on which is riveted several sintered friction pads.
“Normally it’s five or six paddles in something like a 4x4, and we call that a button disc or a paddle disc. They’re normally used for competition-type stuff; it’s not the sort of thing that most people would find comfortable to drive every day.
“But if you’re in a competition or something like that, comfort is not one of the primary factors you’re looking for.”
COMPLETE KIT
WHEN you buy a new heavy-duty clutch kit from ACS, it comes with everything you’ll need to fit it to your vehicle.
“We pride ourselves on supplying all of the required components with every clutch kit; all of the hardware and data for most mechanics to be able to fit the clutch kit confidently, without having to go back and get extra components,” said Stewart.
“In our heavy-duty kits, we always try to supply an alignment tool, if required, to help centre the clutch when installing it. We always try to offer a pilot bearing, a new thrust bearing, and basically offer all of the components that are required to ensure the fitment of that kit goes right the first time ’round.”
“We also supply technical documents that specify any torque settings and anything like that which is critical to fitment. Even things like spline grease, we supply that to ensure people are actually lubricating the spline correctly on the gearbox, and also the release bearing.”
SERVICE LIFE
JUST because you’ve fitted a heavy-duty clutch to your vehicle doesn’t mean it will outlast an OE clutch, but it will still do a much better job.
“Every different product and every different vehicle is going to have a different service life, but I would say that if you’re some level of enthusiast and you have some level of mechanical sympathy, you should be able to achieve 40,000 to 50,000km out of a heavy-duty clutch when using it in a heavy-duty application,” advised Stewart.
“A heavy-duty clutch doesn’t necessarily mean the product will outlast an OEM product for service life; what it does mean, though, is that it will do the job that the OEM product hasn’t been able to do.
“If you put a factory clutch in and it doesn’t hold the torque, and then if you put in a heavy-duty clutch and it does hold the torque, that’s the job of the heavy-duty clutch, to actually outperform the OEM one but not necessarily outlast it.
“Most people understand they need a heavy-duty clutch when they’re going off-road, because the factory ones do fail, but they don’t necessarily understand why.
What we see more and more is the safety factor built into an OE clutch is not necessarily up to the aftermarket modifications that people are making on their vehicles, so that’s sometimes where our product comes into play, because the factory units just don’t last when owners put on all the extra weight and/or increase the torque.”
KEEPING IT COOL
STEWART said a small amount of mechanical sympathy is the best way to look after and extend the life of your vehicle’s clutch.
“You can really abuse the hell out of a vehicle, but if you take it back to 80 to 90 per cent when you’re off-road, and you’re not just ramming the vehicle over things, then you can save components,” he said.
“When you relate that to clutches, anything that generates a significant amount of heat is also going to generate a significant rate of wear. So if you’re riding the pedal trying to get up a hill, rather than engaging low-range and being completely off the pedal, that’s obviously a bad thing.
MORE
4X4 Australia gear“Other things that can cause problems for 4x4 owners are dust or mud or moisture getting into the bellhousing. That can get into the clutch itself and can dry up the release bearing, the pilot bearing, the friction disc... and then you end up with squeaking, premature thrust bearing failure and things like that.
“So going through a creek and completely flooding the bellhousing; that can cause the clutch to slip and become contaminated with muddy river water. We have examples where people may not have put a boot back on to the clutch fork when they’ve reassembled everything inside the bellhousing, and now there’s dust and mud getting in there,” Stewart said.
“But anything like that where you get contamination inside the bellhousing, that’s definitely going to prematurely wear and damage the clutch.”
Although clutch and flywheel selection seems like black magic science, it really is straightforward. When the right choices are made you get an unbeatable clutch and flywheel combo that will serve you well for years to come. In the long run, you will save a bunch of money with the right decision to begin with. And can you afford to make a bad decision? Think about it.
Karl Benz is generally recognized as the father of the automotive clutch, which was invented nearly a century ago. There have been many variations of the humble hard-working clutch in the years since. The clutch’s primary task is to transmit power from the engine’s crankshaft to the transmission smoothly and firmly without slippage. Some slippage is important for smooth engagement, yet without excessive slippage that will cause unnecessary wear and heat issues. You want reasonable pedal effort yet solid engagement, which is what you will get from our Superior clutches.
Clutch selection depends upon the kind of driving you intend to do. If you’re going cruising or doing the workday commute, you need a high-quality diaphragm style single disc organic clutch. Organic clutch frictions provide smooth engagement and longevity in street use. Weekend racing calls for a Kevlar/organic combination. And if you’re real serious about performance driving, a Kevlar high-performance clutch is what you’re going to need to meet the demand.
There are two basic types of clutches — diaphragm and Long style.
The Long Style three-finger clutch was original equipment in a lot of vintage applications. Because the three-finger clutch and pressure plate exert incredible amounts of pressure they also create tremendous amounts of clutch pedal effort. Back in the day a stiff clutch pedal was the norm, but not anymore. Clutch technology has since become such that you don’t have to put up with a stiff clutch pedal (or the resulting knee replacement surgery) anymore. We can’t think of any reason here at Modern Driveline why you should have to put up with a heavy-handed clutch pedal.
If you are looking for more details, kindly visit Clutch Heavy Duty.
The Long Style clutch consists of:
Now that’s a lot of parts!
The Long style three-finger clutch exerts brute pressure on the disc via a series of coil springs between the cover and plate. Spring pressure is the same regardless of engine rpm. Pedal effort is also the same regardless of engine speed. The Long Style clutch is an archaic design at best. It doesn’t make sense to use one anymore.
Diaphragm style clutches, as the name implies, consist of a diaphragm spring that “oil cans” between engaged and disengaged. It is easy to depress yet it delivers whopping hold power. The advantage of a diaphragm clutch is greater clamping power than a conventional three-finger Long style clutch yet without high pedal effort. What’s more, as diaphragm clutch discs wear clamping power increases over the life of the clutch, which improves clutch performance. This is one of the great advantages of a diaphragm style clutch. Another advantage is pedal effort, which is considerably less than a Long style clutch.
Although there are a lot of diaphragm style clutches in the marketplace Modern Driveline brings you a better clutch and here’s why. Modern Driveline brings you greater selection with a complete line of clutches and flywheels from the most trusted names in the industry — Superior and McLeod. We enjoy an extraordinary relationship with Superior Clutch because each clutch is handcrafted for Modern Driveline. Each Superior clutch goes through rigorous testing throughout the manufacturing and quality assurance process resulting in high reliability and performance.
A lot of manufacturers talk about Kevlar clutch frictions, yet in truth their clutch discs contain a very modest amount of Kevlar — some 10-20-percent — which isn’t saying much. Superior Clutch’s disc are nearly 100-percent Kevlar, which can stand extreme punishment and come back for more as hard miles are driven. If you’re a civilized driver your Superior Kevlar clutch from Modern Driveline may well be the last clutch you ever buy. They’re that good.
We can get into a lot of clutch science and physics. However, here’s what you need to know in order to make an educated purchase. There are four Modern Driveline clutch discs from Superior Clutch for your consideration — Organic, Kevlar/Organic, Kevlar/Kevlar, and Kevlar/Metal.
The Superior Organic clutch from Modern Driveline is a basic stock replacement in either 10″ or 10.5″ and with either a standard pressure plate or the brute King Cobra pressure plate. The Superior clutch is economical and well suited to the daily/weekend driver or show car. The Superior Super King Cobra clutch from Modern Driveline features steel backed facings to prevent disc separation common with original King Cobra clutches and heavy abuse.
Modern Driveline’s Superior Kevlar/Organic clutch is a multi-friction type with Kevlar® and Organic surfaces designed with additional grip in mind and high heat tolerance from high performance applications. These clutches are available in 10″ or 10.5″. The Superior Kevlar/Organic clutch is optimum for street and track use.
Superior Clutch’s Kevlar/Kevlar clutch from Modern Driveline is designed for long life and minimal wear under extreme duty conditions. These heavy-duty clutches available in 10.5” are preferable for the high performance, high torque applications. What’s more, they’re preferable for lightweight vehicles prone to clutch chatter.
The Kevlar/Metal discs are designed for high horsepower, drag racing or street performance where “grab” is the name of the game. These are typically considered an “on/off” clutch. You cannot “feather” them for smooth street driving.
Fig. 1: Side by side are the two basic types of clutches — diaphragm (left) and Long style (right). By design three-finger Long style clutches yield a very stiff clutch pedal. Diaphragm style clutches provide a powerful grip without a stiff clutch pedal.
Fig. 2: Two organic clutch discs — coarse tooth (left) and fine tooth (right). Clutch discs are generally designed for application (size and transmission input shaft) the type of use they will experience. Organic clutch frictions are for mild street use.
Fig. 3/4 Here’s why the Long style three-finger clutch gives us such a stiff pedal — powerful springs that provide exceptional holding power. However, they also make it very hard on your left leg and mechanicals because pressure plate holding pressure is transmitted directly to the clutch pedal linkage. This really is an outdated clutch design when there’s a better choice.
Fig. 5 The diaphragm clutch is simply a better piece by design because it gives us great holding power without a stiff pedal. This is a small light-duty diaphragm pressure plate.
Fig. 6/7 Here’s another larger diaphragm clutch and disc for GM applications with fine-tooth clutch disc. .
Fig. 8 The beauty of the diaphragm clutch is simplicity — fewer parts. This link ties the pressure head to the backing plate.
Fig. 9 These coil springs act as shock absorbers in a clutch disc. This is what gives us a smoother engagement as the clutch disc and pressure plate take hold.
Fig. 10 Diaphragm clutch fully engaged with clutch disc compressed.
Fig. 11 Organic and Kevlar clutch discs back to back. On the left is the organic friction disc, which is thicker and heavier. On the right is the lighter and tougher Kevlar disc. Superior Kevlar discs are nearly 100-percent Kevlar designed to take the extremes of racing. Organic discs are strictly for street use.
Fig. 12 From left to right are metallic, Kevlar, and Organic discs
Fig. 13 Here’s the Superior diaphragm clutch with organic friction for street use. The organic disc will not stand up to the punishment associated with racing. This is a coarse tooth hub for vintage Ford applications.
Fig. 14 This is a Kevlar clutch friction in fine-tooth for GM applications. A fine tooth hub provides greater strength because there’s more shaft and hub surface area. Kevlar can be used for street and strip, however, it is primarily a racing clutch. It can take tremendous punishment and come back for more.
Fig. 15 Here’s a closer look at the Kevlar surface. All of our Superior Kevlar clutches are nearly 100-percent Kevlar for extraordinary durability and long life. Kevlar doesn’t look all that intimidating but don’t let looks deceive you. Kevlar is the toughest clutch material available. If you buy it for street use you will never have to buy another clutch.
Fig. 16/17 Here’s a metallic Superior clutch for all-out racing applications. This pressure plate is for GM products. As a rule most GM applications employ a fine-tooth input shaft.
Fig. 18 We also stock McLeod dual-friction diaphragm style clutches for performance applications. Choice depends upon how much power you have and what you want your vehicle to do.
Fig. 19 Here are the input shaft types you can expect to see for domestic applications. These are clutch alignment tools. Two from clutch kits and one copped from a Ford transmission. The steel input shaft works well as a clutch alignment tool. Our Superior clutches come with a clutch alignment tool for your convenience.
Fig. 20 Clutch pilot bushings (right) are typical for OEM installations. Compliment your Modern Driveline clutch installation with a pilot bearing (left) for precision function and smooth clutch operation. While you have your vehicle apart check the engine oil pan gasket, rear main seal, and transmission input shaft seal for leakage. Any leakage issues must be handled at this time or you wind up with clutch disc contamination.
Fig. 21 Clutch release bearing to diaphragm alignment must be spot on for proper function and longevity. Diaphragm style clutch release bearings are constant duty parts meaning they’re in contact with the diaphragm at all times.
Fig. 22 Compliment your new Superior clutch installation with a new flywheel from Modern Driveline. This is money well spent because every new clutch deserves a new flywheel surface. We stock steel, billet, and aluminum flywheels for nearly every application imaginable.
This is why you do business with Modern Driveline. We are not a large company with huge product development teams with bean counters and Wall Street investors looking over our shoulders. We are automotive enthusiasts bent on getting our products right before they’re ever sold to the public. We are also very determined to deliver great technical support after the sale. As a Modern Driveline customer, you will never be our guinea pig. We find problems before they get to you and solve them before they ever become a headache for you.
We don’t just find the fault — we find the fix at the prototype phase before products ever reach the mass production phase. And if you ever encounter a problem with any of our products, we invite your contact so we may solve it before it ever becomes a frustration for you. If there is a problem after the sale, we are here to provide lifetime technical support for any Modern Driveline product you buy.
If you’re looking for more information or a quote for your project send us your details and we’ll get back to you with a quote. Or call…
Want more information on Truck Oil Filter? Feel free to contact us.