What’s a Throwout Bearing? We Tell You Here!
Oct. 31, 2023
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Technically speaking, the correct terminology for a throwout bearing is release bearing, as in clutch release bearing. When considered in those terms, it's easier to imagine what this component is and what it does. The throwout bearing is the last piece in the series of components that composes the clutch linkage from the pedal to the clutch assembly inside the transmission bellhousing.
It's a bearing, meaning that it allows interaction between a moving surface and a stationary surface. Just like wheel bearings allow movement of the spinning wheel hub around the non-moving spindle, the throwout bearing is the component that comes between the clutch pressure plate, which is spinning when the engine is running, and the non-moving clutch fork- or the hydraulic slave cylinder typically found in newer cars. Although there are a few different ways a clutch can be actuated, mechanical or hydraulic, the function of the throwout bearing is the same. It connects moving and non-moving parts.
The throwout bearing is made up of a base, which is attached to the linkage assembly, the outer shell that pushes against the pressure plate, and the bearing assembly located between the two.
In a clutch assembly, the pressure plate is bolted to the flywheel and is rotating any time the engine is running. The friction disc slips over the splines of the transmission's input shaft and only turns when the drive wheels are turning.
The release bearing is held by the stationary clutch fork and, when the clutch pedal is pressed, pivots forward to contact the diaphragm spring of the pressure plate, which act like a lever to disengage the clutch, separating the mechanical link between the engine and the transmission's input shaft.
Clutch linkages are either mechanical or hydraulic. Hydraulic clutch systems will have either an external slave cylinder or an internal slave cylinder. Mechanical systems include actuating rods and a bellcrank, commonly referred to as a Z-bar, or via a cable between the pedal and clutch fork.
Most cars made since the late '90s have hydraulic clutch systems with an internal slave cylinder, meaning the slave cylinder is located inside the transmission bellhousing.
The slave cylinder is housed within the base of the bearing assembly. When you press the clutch pedal, fluid from the clutch master cylinder is forced through hydraulic lines into the base and to a piston below the bearing assembly. That forces the bearing surface to push the diaphragm springs of the pressure plate. In this photo, the long tube is the bleeder fitting, the fluid inlet port is located below it.
The bearing surface of many internal slave cylinders is designed to maintain contact with the pressure plate. Its outer surface is always spinning, whether the clutch is engaged or disengaged. It is self-adjusting, meaning that the spring between the bearing and base puts tension on the bearing, keeping it in contact with the pressure plate. This accommodates for clutch wear.
Some bearings of internal slave cylinders are not designed to be constantly spinning. In this case, an air gap is required between the spinning clutch assembly and the throwout bearing. The same is generally true for a system that includes a clutch fork, whether that system is fully mechanical or hydraulic. Specific air gap specs depend on application but can be found in a service manual or instructions included with the kit.
A crude but effective example of how a throwout bearing works is demonstrated on a common rolling work stool. Because the seat spins freely, we're using it as a stand-in for the engine's flywheel. The pressure plate bolts to it with the friction disc sandwiched in between. With your author's hand as the clutch fork, notice how the base of the throwout bearing remains stationary as the face spins with the pressure plate. Pushing on the pressure plate diaphragm spring disengages the clutch.
Symptoms of a Bad Throwout Bearing
The throwout bearing is a simple device that should provide years of long life. It is made with a sealed bearing assembly that doesn't require maintenance or lubrication. When a bearing goes bad, you will hear a grinding or whirring noise whenever the bearing is spinning. In a system where the bearing is in constant contact with the pressure plate, you will hear the noise all the time, though it may be louder when the clutch pedal is pushed in, putting the greatest load on the bearing surface. In systems with an air gap between the bearing and pressure plate, you will only hear the noise when the clutch is pushed in and the bearing is spinning. The sound will go away when you take your foot off the clutch pedal. If your throwout bearing is bad, you have no choice but to remove the transmission to replace it. That's why it can cost so much money to replace an inexpensive part.
Clutch Thrust/Release Bearing – Inspection & Replacement
What is the clutch thrust bearing?
The clutch thrust bearing (also known as the release bearing or the throw-out bearing) is a small but important part of your car’s clutch system. It is mounted on the housing of your clutch and slides on a hollow shaft. Attached to the clutch bearing is the clutch fork, which moves the clutch bearing with the help of hydraulic or cable pressure.
While the clutch pedal is pushed down, the bearing moves inward. The bearing will apply pressure to the spring of the pressure plate, freeing the clutch disc from the flywheel and interrupting the transmission. This allows you to correctly and safely engage and switch gears.
Enhance Performance and Smooth Shifting with Clutch Thrust Bearing Replacement
What causes clutch thrust bearing problems?
In most vehicles, the clutch bearing isn’t a scheduled maintenance item. This means that it usually lasts the life of the vehicle. However, the clutch thrust bearing can become worn over time, especially in older vehicles. This is due to constant contact with other parts and exposure to heat and cooling, worn off clutch lining dust entering the clutch trust bearing through failure / damage to clutch thrust bearing seals.
Another common cause of damage to the clutch trust / release bearing is if the clutch cable is not adjusted over time, and the clutch release / throw out bearing is in constant contact with the clutch pressure plate. This will cause it to constantly spin reducing it’s life dramatically.
Clutch cable adjustment services in Hamilton
Improper clutch use can shorten the life of clutch components such as the thrust bearing. Examples of improper clutch use include:
Not starting your vehicle in first gear
Downshifting several gears at a time (4th to 1st)
Skipping gears (1st to 3rd)
Symptoms of a failing clutch thrust bearing:
Unusual Noise: One of the most noticeable symptoms is a grinding, squealing, or whining noise when you depress the clutch pedal. The noise may occur when you engage or disengage the clutch, or it may persist while the clutch pedal is held down. This noise is usually caused by the failing bearing not spinning smoothly or having worn-out components.
Clutch Pedal Vibration: A failing thrust bearing can cause vibration or pulsation in the clutch pedal when it is depressed. This vibration can be felt as an abnormal sensation through the pedal.
Difficulty Shifting Gears: A failing clutch thrust bearing can make shifting gears more challenging. You may experience difficulty engaging or disengaging gears smoothly, and there may be resistance or grinding when attempting to shift.
Clutch Slippage: As the thrust bearing wears out, it can lead to clutch slippage. This means that the clutch fails to fully engage and transmit power from the engine to the transmission. You may notice a loss of acceleration, a decrease in engine power, or the engine RPMs increasing without a corresponding increase in vehicle speed.
Clutch Drag: A failing thrust bearing can also cause clutch drag, which means the clutch does not fully disengage when the pedal is pressed. This can result in difficulty shifting into neutral or when changing gears, as there may be resistance and grinding.
Abnormal Clutch Engagement Point: The clutch engagement point, the point at which the clutch begins to engage after releasing the pedal, may feel inconsistent or different from normal. It may be higher or lower than usual, making it harder to find the right engagement point.
Clutch thrust / release bearing replacement in Hamilton
Are you experiencing unusual noises, difficulty shifting gears, or clutch-related issues in your vehicle? It might be time to consider a clutch thrust bearing replacement.
At Grimmer Motors, our trustworthy mechanics are skilled in all sorts of clutch bearing related services. This allows us to quickly identify, diagnose and fix clutch bearing problems in your vehicle.
Benefits of clutch thrust/release bearing replacement:
Enhanced Clutch Engagement: A worn-out or failing clutch thrust bearing can lead to inconsistent clutch engagement, making it difficult to find the right engagement point and resulting in rough shifting. By replacing the thrust bearing, you can restore smooth clutch engagement, allowing for precise gear changes and seamless transitions between gears. Whether you’re cruising on the highway or maneuvering through city traffic, a properly functioning thrust bearing ensures smooth clutch operation.
Elimination of Unwanted Noises: One of the most common signs of a failing clutch thrust bearing is the presence of grinding, squealing, or whining noises when operating the clutch. These noises can be distracting, annoying, and indicate potential damage to other clutch components. By replacing the worn-out thrust bearing, you can eliminate these unwanted noises, promoting a quieter and more enjoyable driving experience.
Prevention of Further Damage: A failing thrust bearing can cause additional wear and tear on other clutch components, leading to more extensive and costly repairs in the future. Ignoring a worn-out thrust bearing can result in clutch slippage, difficulty shifting gears, and even clutch failure. By proactively replacing the clutch thrust bearing, you can prevent further damage to the clutch system, saving you time, money, and potential breakdowns on the road.
Improved Performance and Safety: A properly functioning clutch system is vital for the performance and safety of your vehicle. A worn-out thrust bearing can negatively impact clutch engagement, shifting responsiveness, and overall driving performance. By replacing the thrust bearing, you can restore the clutch system’s efficiency, enhance vehicle control, and improve the overall safety of your driving experience.
We can replace your clutch release / trust / throw out bearing for you, allowing your stick shift / manual transmission to run correctly. For clutch release / thrust bearing replacement in Hamilton, contact Grimmer Motors today!
Please note: We do not stock and sell parts. We are an automotive repair shop that orders parts on a per-job basis. If you want us to order and install a part, feel free to get in touch
Troubleshooting common issues with heavy duty clutch bearings
We get it. Your wheel bearings are not at the top of your fleet inspection checklist, but just like your engine, transmission, or tires, ignoring proper maintenance procedures of your wheel bearings can cause damage.
The failure of your truck’s clutch bearings, for example, could sideline it and potentially cause further damage to the entire clutch pack assembly.
Let’s take a closer look at the bearings’ role within the clutch.
Two different bearings are incorporated into the transmission–the clutch pilot and the clutch release.
While engaged, the clutch pedal is at full height while the pressure plate forces the friction disc against the flywheel. The friction disc turns the Splined Input Shaft which drives the transmission to power road wheels.
While the clutch system is disengaged, the clutch release bearing is moved forward by the clutch fork. As the pressure plate compresses and the friction disc uncouples, the friction disc and input shaft are no longer being turned by the engine. The clutch pilot bearing rotates if there is difference between rotation.
To avoid a costly breakdown, here are some warning signs that indicate struggling clutch bearings that you may want to be on the lookout for.
Clutch pilot bearing
– Grinding sounds as the vehicle is accelerating/decelerates after the clutch pedal is fully engaged;
– Steering wheel vibrations as the vehicle accelerates; or
– Bad smells as the clutch bearing begins to heat up.
Clutch release bearing
– Whining/grinding during press/release of clutch pedal
– Clutch becoming stiffer as lubrication properties diminish
– Difficulty shifting gears in manual transmission
If you begin noticing the above observations, it may be time to replace your clutch bearings. Putting in the effort now to ensure your bearings are in working order and can meet application requirements will spare you unprecedented downtime later on.
The ever-increasing marketplace demand means it’s more important than ever to ensure your fleet is achieving optimal performance and dependability.
In order to achieve this, it’s important to double-down on equipment details. When it comes to bearings, the installation is simple, but the components are produced specifically to meet the tedious demands of operating conditions.
Before installation, it’s important to note the difference between high-temperature and standard clutch bearings and the applications they can be used for as they are not always interchangeable. To better understand which choice is best for your trucks and applications, check out the Bower’s video on the “Differences Between Standard Temp & High Temp Clutch Pilot Bearings” on the Bower Bearings YouTube channel.
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