Manual Transmissions/Drive Axles

Clutches

These days, very few vehicles have a manual transmission. But if your car is one of the few that do, you can expect its clutch to wear out eventually.

Much like brake pads, a clutch is considered a wear item, meaning it’s not designed to last the life of the vehicle. When your car’s clutch begins to wear out or experience premature failure, you may start to notice symptoms, such as clutch slippage. If your car’s clutch is slipping, the symptoms will be fairly obvious. Clutch slippage results in an increase in engine speed without a corresponding increase in vehicle speed. While driving, you’ll notice the engine races, but the car does not go any faster. This is because the slipping clutch is disrupting the flow of power between the engine and transmission. To fix a slipping clutch, it must first be determined what’s causing the slippage in the first place. Clutch slippage can be caused by excessive clutch pedal free play, fluid-contaminated mating surfaces, a worn-out friction disc, or a weak pressure plate.

Once you determine the cause of the concern, you can perform the necessary repairs to fix the vehicle. Usually (but not always), the fix will be to replace the clutch assembly.

Flywheels

A manual transmission might seem like a basic mechanical design. You do all the work to shift gears, don’t you? But what you don’t see are all the parts that are constantly in motion to keep your car under your control. One of those parts is the flywheel. In a vehicle with a manual transmission, the flywheel serves a crucial purpose.

A FLYWHEEL’S CONSTRUCTION

In a manual transmission, the flywheel is a thick metal disc.
It’s typically made of cast iron, steel or, in some cases, aluminium.
It’s extremely rigid to prevent flexing or warpage during use. The edge of the flywheel has a row of gear teeth that engage with the engine’s starter motor.

The flywheel is firmly bolted to a flange on the transmission side of the crankshaft inside the bell housing. On the side facing the manual transmission, the surface is machined flat for the clutch disc to grab onto.

WHAT THE FLYWHEEL DOES

But what does the flywheel do? It actually has a few different purposes:
The flywheel provides mass for rotational inertia to keep your car’s engine running. Otherwise, the engine will stall when you let your foot off the accelerator. It balances the engine. A flywheel is specifically weighted to the car’s crankshaft to smooth out the rough feeling caused by even a slight imbalance. It allows for an electric starter. The starter motor engages the starter ring on the edge of the flywheel to begin engine rotation.

Most importantly for drivers, the flywheel connects the engine with the transmission via a clutch to transfer power to the wheels. When your foot is on the clutch pedal, the clutch disc is disengaged from the flywheel. This is how a car can sit still at idle with the shifter in gear, or how a car can coast to a stop. But when the pedal is released, the clutch disc will press firmly against the flywheel. When this happens, the transmission input shaft rotates at the same speed as the engine’s crankshaft.

WHAT PROBLEMS CAN HAPPEN WITH THE FLYWHEEL?

Due to its heavy-duty construction, a flywheel is extremely durable. That’s not to say that problems can’t occur, just that they’re less frequent.
Among the most common flywheel problems that can come up is contamination. A leaking rear main crankshaft seal or a transmission front input shaft seal can leak oil onto the flywheel. It causes clutch slippage and excessive friction and heat. Warpage or hot spots can result, creating a vibration on engagement and acceleration.

In extremely rare cases, a flywheel can crack due to hard use in high-performance or heavy-duty vehicles. Sometimes, the flywheel can be resurfaced to restore a flat, even surface for the clutch to mate to if the concern is warpage or hot spots. If resurfacing the flywheel isn’t possible, replacement is the only other repair. It’s also a great time to change the clutch if it’s nearing time to replace it.

Clutch Master Cylinder

The clutch and brakes on a car need a little help to actuate, considering the forces that they are designed to oppose, therefore hydraulic pressure is created within the master and slave cylinders to provide the required force.

The master cylinder can be found directly behind the pedal box, connected to a respective pedal. The slave cylinders in a car are therefore used to finish the amplification of the forces from your foot inputs through to the clutch and brakes respectively. In the case of the clutch, the slave cylinder actuates the clutch fork to disengage the clutch friction plate from the flywheel, with a return spring reversing the process. And the slave cylinder found at each set of brake calipers on a car is used to close the brake pads around the brake disc. To add assistance to the braking system, a brake servo sits in front of the master cylinder and uses the vacuum created within the inlet manifold to further amplify the hydraulic pressure within the braking system.

Master and slave cylinder failure can be a bit of a nightmare, with most faults coming from leaks in hydraulic fluid leading to a lack of pressure. This can lead to a gear change becoming incredibly difficult to perform as the force being applied through the clutch pedal is simply not enough to efficiently actuate the clutch fork. Therefore a faulty slave cylinder can render a car nearly undriveable if failure occurs. Obviously a hydraulic fault like this within the braking system can be even more catastrophic, which is why the master cylinders are engineered with a certain safety factor using the secondary piston within the mechanism.

If you ever feel like your clutch has ‘gone’ due to an extremely stiff gear change which may even result in a grinding of gears, the chances are it’s probably a hydraulic failure from either the master or slave cylinder. Possibly it’s just a small hydraulic leak that needs to be repaired followed by a quick reservoir top-up, or it could be genuine damage to the piston or spring mechanisms within the cylinders. So next time you press down on either the brake or clutch pedals, you’ll now know exactly what’s going down!

Slave Cylinder

The clutch and brakes on a car need a little help to actuate, considering the forces that they are designed to oppose, therefore hydraulic pressure is created within the master and slave cylinders to provide the required force.

The master cylinder can be found directly behind the pedal box, connected to a respective pedal. The slave cylinders in a car are therefore used to finish the amplification of the forces from your foot inputs through to the clutch and brakes respectively. In the case of the clutch, the slave cylinder actuates the clutch fork to disengage the clutch friction plate from the flywheel, with a return spring reversing the process. And the slave cylinder found at each set of brake calipers on a car is used to close the brake pads around the brake disc. To add assistance to the braking system, a brake servo sits in front of the master cylinder and uses the vacuum created within the inlet manifold to further amplify the hydraulic pressure within the braking system.

Master and slave cylinder failure can be a bit of a nightmare, with most faults coming from leaks in hydraulic fluid leading to a lack of pressure. This can lead to a gear change becoming incredibly difficult to perform as the force being applied through the clutch pedal is simply not enough to efficiently actuate the clutch fork. Therefore a faulty slave cylinder can render a car nearly undriveable if failure occurs. Obviously a hydraulic fault like this within the braking system can be even more catastrophic, which is why the master cylinders are engineered with a certain safety factor using the secondary piston within the mechanism.

If you ever feel like your clutch has ‘gone’ due to an extremely stiff gear change which may even result in a grinding of gears, the chances are it’s probably a hydraulic failure from either the master or slave cylinder. Possibly it’s just a small hydraulic leak that needs to be repaired followed by a quick reservoir top-up, or it could be genuine damage to the piston or spring mechanisms within the cylinders. So next time you press down on either the brake or clutch pedals, you’ll now know exactly what’s going down!

Release/Throw-Out Bearings

If your vehicle has a manual transmission (a rarity these days), you need to be able to operate a clutch pedal in addition to the brake and gas pedals. The clutch assembly (consisting of the pressure plate, clutch plate, flywheel, and throw-out bearing), connects the wheels to the engine of the vehicle. The clutch pedal gives you the ability to temporarily disconnect the wheels from the engine which is needed when shifting gears.

The throw-out bearing, sometimes called a “clutch release bearing”, is a simple yet important component that’s only in use when the clutch pedal is depressed. When you have a bad throw-out bearing, it will affect shifting and can lead to failure of other clutch and transmission components.

How a Throw-Out Bearing Works

In short, a throw-out bearing is the component of the clutch which temporarily disengages a car’s engine from the transmission during gear shifts. When you push the clutch pedal with your foot, the clutch release bearing gets closer to the flywheel. This causes the release fingers of the pressure plate to get pushed in. Once that happens, the fingers of the pressure plate push against the force of its spring. This causes the disconnect between the engine and wheels and allows you to shift into a different gear. When the clutch pedal is released, the throw-out bearing returns to its original position where power from the vehicle’s engine once again is transferred through the transmission into the drive wheels of a car.

All the components of the clutch and transmission system are important for the safety and functionality of the vehicle. If your throw-out bearing is unable to do its job properly, you’re going to notice some signs of it starting to go bad or complete failure. The bearing may go bad after years of wear and tear or maybe even from damage due to an accident. In any case, you need to get the clutch release bearing replaced as soon as you notice it’s having problems.

Transmission Repair & Replacement

A car’s transmission consists of an incredible amount of parts. Each component of the transmission is important. However, each component of a car’s transmission can wear or take damage independently of every other part of the transmission. A transmission repair will replace only the parts needed to get your transmission back up and running.

The main concern with a repair of this nature is it may not solve an underlying issue. The transmission may have too much damage, which can make a small repair akin to a stopgap measure that will only become a problem again sooner than later.

Often, repairs work best when the problem is a surface level issue. If a technician has to disassemble the transmission and all its subassemblies, the process can take more time and cost more as well. When the technician must dig deep into the transmission to find the problem, a transmission rebuild can become a better option. We always try our best to look out for your interest and make recommendations that will keep your vehicle on the road and agree with your wallet.

Transmission Fluid & Leak Repair

It’s possible to drive your car when its leaking transmission fluid, but it’s probably not a good idea since your vehicle won’t drive as required.
Putting safety into consideration here are a few factors you need to consider:

A common reason why your vehicle could be leaking is a gap in your transmission system. It’s very hard to narrow this down since it could be a space in the gasket, fluid lines, torque converter, seals or transmission pan. It is therefore advisable to consult the services of a professional mechanic.

It doesn’t matter the amount of fluid leaking, the moment you notice transmission fluid leaking onto your driveway, get the leak fixed immediately. If ignored, the problem could escalate over time, leading to a transmission breakdown. Fixing a small leak is fairly easy compared to a big one.

Seals: What are Transmission Seals?

The input shaft seal, also called the front transmission seal, prevents fluid from slipping past the input shaft. The input shaft inserts into the torque converter or clutch disk, depending on whether the vehicle is equipped with an automatic or manual transmission. The output shaft seal, sometimes called the rear transmission seal or driveshaft seal, prevents fluid from escaping where the driveshaft yoke slips into the transmission. Front-wheel drive vehicles have two “rear” transmission seals, one for each axle.

How do Transmission Seals Work?

The seals have two important dimensions, the outside diameter and the inside diameter. A seal with the proper outside diameter fits tightly into the recess on the transmission. The inner diameter of the seal has an interference fit along with a tiny spring to keep it snug against the input shaft or the driveshaft. When the input shaft or the driveshaft is inserted into the transmission, the seal locks fluids inside. The seal is designed to prevent leaks regardless of how fast the input shaft or driveshaft spins.

How are Transmission Seals Made?

Transmission seals are made of rubber and plastic. Some seals are reinforced with steel. Most seals have a very small spring around the inside diameter to help produce an interference fit with either the input or the output shaft. Manufacturers produce these seals in bulk using heavy, factory grade machinery.

Why do Transmission Seals Fail?

Oxidation causes rubber and plastic seals to lose their flexibility, resulting in cracks and eventual fluid leaks. Transmission seals may fail prematurely, or not seal at all, if they are installed improperly. Bearing wear inside the transmission damages the seals, causing leaks.

What are the Symptoms of Seal Failure?

Automatic transmission fluid (ATF) spots or puddle under the vehicle. ATF is red, reddish, or brown and has a distinctive smell. Gear oil or motor oil spots or puddles under the vehicle. The transmission may slip or make excessive noise as fluid loss accelerates.

What are the Implications of Seal Failure?

If left unchecked a small leak may develop into a large leak. Large leaks may result in damage to the transmission if they are not diagnosed and repaired in a timely manner. The seals on your vehicle’s transmission are an important part of keeping your drivetrain in good working order. Avoid damage to major components by catching leaks early.

Shift Linkage Repair/Replacement

All automatic transmissions have basically the same shift linkage on the transmission itself. The shift linkage between the cabin and the transmission varies between vehicles, but still has the same function. There is a column shift and a floor shift that are both cable operated. Shift levers have even been placed on the dash on several SUVs.

Detents

The arm on the transmission that is used to change gears will be common. As the lever is rotated, there will be definite detents for Park, Reverse, Neutral, Third or Drive, Second and First gears. On many transmissions, there will be a Fourth or overdrive detent. It all depends on the vehicle, but it still only uses a detent. On many vehicles, a button on the gearshift handle controls the overdrive function via a solenoid.

Lockout

All vehicles today come with a lockout device that does not allow the vehicle to be shifted out of “Park” unless the brake is depressed. This is for obvious safety reasons. A small electrical solenoid actuates on the steering column or floor shifter when the key is on and the brake is depressed, freeing the shift lever so it can be moved. In the case of a column shift, when the shift handle is pulled down, the detents can be felt in each gear.

Shift Lever

The indicator on the dash that shows the gear position of the handle is a small needle attached to a nylon cord. It is attached with a spring clip on the barrel of the column that turns with the handle. As the handle is pulled down, the barrel rotates clockwise and pulls on the indicator, dropping it into a lower gear. As the handle is raised, a spring pulls the indicator back toward park.

Column Shift

On a column shift, a rod runs from the handle straight down, and has a lever attached to the end of it near the brake pedal arm. The shift cable runs up through the firewall and attaches to this lever. The cable runs from the firewall to the transmission gear shift linkage, where it is attached and held securely in place. As the handle is moved, it either pulls or pushes on the cable. In turn, the cable does the same to the transmission linkage.

Floor Shift

A floor shift linkage operates by pushing or pulling on the cable by the forward and backward movement of the lever handle. If the cable ever needs to be replaced, make sure that the transmission (the gear shift on the side of the transmission) is in “Park.” When replacing the cable, make sure the shifter is also in “Park” like the transmission. Install the cable so that it fits loosely onto the transmission lever, and is secure. If the cable is left to flop around, it will flex every time the shifter is moved, and will be ineffective in changing gears.

The Signs & Symptoms of a Bad Shifter Cable

A number of current and late model vehicles use cables to link the shifter handle to the transmission. Vehicles with automatic transmission typically have one transmission cable, while vehicles equipped with manual transmissions typically have two shifter cables. The concept of what the shifter cable does is the same regardless of the type of transmission your vehicle is equipped with – the symptoms, on the other hand, are completely different.

What the Shifter Cable Does

Automatic transmissions have a single shift lever that is linked to the manual valve in the valve body of the transmission. This lever is pushed and pulled on a single plane into a number of different positions as you move the shifter handle inside your vehicle. Manual transmissions have two shift levers — one for vertical movement and one for horizontal movement of the shifter assembly on the transmission. The horizontal lever is pushed or pulled by one cable, moving along a single plane with three positions. The second, or vertical lever typically moves the shifter assembly on the transmission up and down. When you move your shifter toward the front or rear of the vehicle, the shifter cable moves the horizontal lever. Moving your shifter left or right pushes or pulls the other cable, moving the shifter assembly up and down. If you have a six-speed manual transmission, your vehicle may have a third shift cable that moves a lock-out lever. This cable is only used when you press a button or push down on the shift lever to engage reverse.

Why Cables Fail

The most common reason for failure of a shift cable is stretching. It is more common in vehicles with manual transmissions because you move the shifter more frequently; you don’t just set it and forget it as you do with an automatic transmission. Cables have also been known to break, or under some circumstances bend, preventing them from moving the shift lever on the transmission into the correct position for the selected gear. If you speed shift either type of transmission or slam gears of a manual transmission, you will cause accelerated wear of a shifter cable.

Symptoms of a Bad Automatic Transmission Shifter Cable

If your vehicle’s gear position indicator isn’t electronic, you’ll notice the indicator needle doesn’t line up correctly with the gear you’re actually in. As the cable stretches over the life of your vehicle, you may notice that the needle will point to reverse while you’re in park, or positioned between reverse and neutral when you’re in reverse. Sometimes you’ll have a little bit of play in the shifter, even though the transmission is already in gear. When the cable stretches too far, you may not be able to properly engage park, or manually select first gear. When the cable is stretched this much, it can also prevent you from turning the ignition all the way off, or removing the ignition key. Because all automatic transmissions are equipped with a park-neutral safety switch, a stretched cable can prevent the engine from starting in park and neutral or allow it to begin cranking while the transmission is in any other gear.

If your car doesn’t seem to want to go into gear at all, it might not be a faulty transmission – It could just be a broken shifter cable. If the cable is broken, you’ll be able to move the shifter into any position, but the transmission will stay in the same gear. This may leave you stuck in gear, or even stuck in park depending on when the cable broke. There is a quick test you can perform. If the vehicle doesn’t go into any gear, shift the transmission into neutral and try to push the vehicle a couple feet. If you can only rock the vehicle, but your indicator says neutral, the cable is probably broken.

Some automatic shifter cables can be adjusted. If the cable is out of adjustment, you’ll experience the same symptoms as you would if the cable was stretched.