How Gears Work

All vehicles have gears, where they are located and how they interact varies depending upon the application. A gear set allows the movement of rotational pieces from one particular axis to another. By gears turning and connecting to each other it allows energy and movement from one gear to another. This means it is possible to use gears to transfer energy to any desired axis.

Another reason gears are used is to help either decrease or increase the speed of rotation. For example, taking a large diameter gear and using it in conjunction with a small diameter gear will speed up the rotation, while in reverse using a small gear in conjunction with a large gear will slow the rotation down. Gears are often used as a method of changing the direction of the rotation. Through a series of gears, it is possible to take a counter clockwise rotation and change it into a clockwise rotation without any loss of power or rotation speed.
The way in which the gears work together based upon their size is called gear ratio. This ratio is determined based upon counting the number of teeth on the gear. For example, if one gear has 20 teeth and the gear it is connected to has 40 teeth then the gear ratio is 20 to 40 which is also written as 2:1. These numbers are purely for example purposes only and will vary in actual usage depending upon the size of the actual gears being used.

One of the largest gear sets inside of your vehicle is the transmission. Automatic transmissions make specific noises when a malfunction is occurring. An automatic transmission

is a hydraulic pressure driven system that can make different noises than a manual transmission. If the transmission filter becomes plugged do to debris in the transmission, it can make a whining noise. If the fluid level is low it can cause a gurgling sound, this sound is due to the pump scavenging for fluid inside the transmission pan. Most internal failures are due to bearing, clutch or hard part failure. When such a failure has occurred the transmission can make grinding, worrring or no noise at all. When a transmission has a major failure you might hear a loud pop, this could be a drive component inside the transmission has failed causing the vehicle to stop moving.

Maintenance
Inspect fluid levels to protect gears, to have clean, debris free fluid while using high quality oil. Ensuring that these fluids are full as well as changed in accordance with your maintenance schedule is the single best maintenance you can do.

How an Automatic Transmission Works

There are two types of transmissions most commonly used today, automatic and  manual (stick shift). Most automatic transmissions have a service filter in the  transmission pan that should be changed at manufacturer specified intervals. When servicing an automatic  transmission a complete fluid flush is recommended to clean the many passages  inside an automatic transmission and to get the fluid that is trapped in the torque  converter.
The driver selects a mode by maneuvering the gear shift lever, usually placed  on the steering column or next to the driver's seat in the center console. In most  cars it is necessary to depress the brake pedal before the gear selector can be  moved from the Park position. Gear selection options usually include (P)park, (R)reverse,  (N)neutral, (O)overdrive, (D)drive, (2)second and (L or 1)first gear in that order.  The park or P mode locks the transmission mechanically. This restricts movement  of car in any direction. This is achieved using a metal rod that engages the output  shaft and prohibits movement.
An automatic transmission functions by automatically changing the gear ratios  while determining the speed and load of the engine. Automatic transmissions have  been available since the 1950s. The automatic transmission is controlled by selecting  a desired gear from the hydraulic gear engagement system.

Automatic Transmission Gear Range Selector

 

Inside the Automatic Transmission

The automatic transmission consists of: a transmission case, planetary gear-sets,  valve body, fluid cooler (in radiator) and a torque converter or fluid coupler.  A torque converter utilizes transmission fluid as a coupling agent allowing the  engine to run while the car is stopped without stalling the engine, then re-engaging  to make the car move again once the RPM of the engine has increased. A series of  clutches and band controlled planetary gear sets provide multiple forward gear ratios  with a set reverse gear. The valve body is the hydraulic control center that receives  pressurized fluid via the main transmission pump. This system is controlled by the  PCM (power control module) in newer cars and mechanically in older ones (Pre-computer  controls).

Automatic Transmission cut-away Image

To prevent damage to the transmission the car should be at a complete  stop before engaging the Park mode. Park mode is also one of the modes in which  the car can be started; the other is the N or neutral position.

The neutral or N mode is used to disengage the transmission from  the drive wheels to let the car move freely. The drive or D mode allows the car  to vary its speed through a range of forward gears, usually 4 forward gears exist,  but companies like Audi, BMW, Lexus and Mercedes Benz have developed a direct shift  gearbox that has up to 8 forward gears.

The D4 mode is best suited for highway speeds and D3 can be used  for around town driving. The first, 1 or L mode is meant to lock the transmission  in first gear. In this mode a vehicle will move slowly but have more power that  can be used when towing or on steep grades. The second, 2 or S mode is used to lock  the transmission in the first two gears. This is used in extreme weather conditions  like ice and snow and to govern vehicle speed.

Automatic Transmission Computerized operating system with ABS Brake System

 
Automatic transmissions make specific noises when a malfunction  occurs. An automatic transmission is a hydraulic pressure driven system and it will  make different noises than a manual transmission. If the transmission filter becomes  plugged due to debris, it can make a whining noise. If the fluid level is low, you  might hear a gurgling sound, caused by the pump scavenging fluid inside the transmission  pan. Most internal failures are due to bearing, clutch or hard part failure. When  such a failure occurs the transmission can make grinding, whirring sounds or no  noise at all. When a transmission has a major failure you might hear a loud pop  which could mean a drive component inside the transmission has failed and the car  will stop moving.

Some manufacturers have developed a continuously variable transmission  or CVT. This type of transmission has become popular during the past few years.  Instead of having set gear ratios, the system can change the amount of forward acceleration  over a wide range of speeds. Two cones or wheels of varying diameter are used to  change the gear ratio. Hydrostatic drives use a variable displacement pump and hydraulic  motor to vary the ratio continuously according to the amount of throttle being given  and the amount of load on the vehicle.

Popular Problems Checks
1. Car will not go into gear:

• Gear selector cable has failed
• Brake lock solenoid/brake light swtich has failed not allowing the gear   selector to move out of "Park"
• Excessively low transmission fluid (note: if car is operated for an extended   amount of time with low fluid level the transmission will fail prematurely)
• Shorted electrical component not allowing the PCM to control the transmission.   Example: shorted fuse
• Flex plate (flywheel) is broken completely not transferring engine power   to the transmission.

2. Car goes into gear but then fades out of gear or is slipping while driving:

• Transmission fluid is low
• Transmission clutch discs or bands are worn out or burned
• Faulty transmission shift solenoid.

3. Car goes into gear but does not shift out of first:

• Blown fuse to the PCM controller
• Faulty vehicle speed sensor (VSS)
• Shorted second gear control solenoid
• Faulty transmission controller (PCM)

Tips About Common Problems and Fixes

• When the vehicle is cold or going around corners the transmission fades   in and out of gear: In most cases this means the transmission fluid is   low. The transmission will lose hydraulic pressure causing the transmission   to drift in and out of gear. Check your transmission fluid when the car is on   flat ground with the engine idling in park (some Chrysler products must be checked   in neutral), add fluid as needed and recheck level.
   
• Transmission is shifting too late or not at all. On most cars the   transmission is controlled by the PCM (powertrain control module) if the vehicle   speed sensor fails the PCM has no input so the computer will not shift the transmission   properly. The best way to check this sensor is to make sure the speedometer   is operating correctly. If it isn't, replace the VSS and recheck. On older cars   the transmission shifting is controlled by either a vacuum modulator or a throttle   control valve cable (TV Cable). If the vacuum is impaired to the modulator or   the throttle valve cable has failed the transmission will not shift correctly.
   
• The transmission skips second gear, shifts from first gear to third gear   and the "service engine soon" MIL is illuminated.  Scan the PCM to locate the   transmission control solenoid that has malfunctioned, replace the solenoid then   clear trouble codes and recheck operation.

Fluid Level and Leaks

Transmission Planetary Gear Set
One of the most common complaints with an automatic transmission  is leaking fluid. Leaks can occur from the driveshaft seals, the input shaft seal,  pan gasket, or the ATF (automatic transmission fluid) cooler or line connections.  When adding transmission fluid, do not overfill. Doing so could cause the fluid  to become aerated, which will affect transmission operation. If there are no visible  leaks, check the radiator for ATF in the coolant. The ATF cooler inside the radiator  may be leaking and cross-contaminating the radiator coolant. You should also check  the condition of the fluid, some discoloration and darkening is normal as the fluid  ages, but if the ATF is brown or has a burnt smell, it is badly oxidized and a transmission service  needs to be performed.

Most transmission problems can be prevented by changing the ATF and filter according  to manufacturer specifications. In extreme conditions installing an aftermarket  auxiliary ATF cooler parallel to the OEM ATF cooler is recommended. This prevents  fluid overheating on vehicles used for towing or performance applications.

Fault Codes:
Fault codes can be set when the transmission controller or PCM detects a malfunction.  Codes can be set by the computer when a command is sent, such as a 2-3 shift, but  the transmission does not respond.

Diagnostic Procedure

•   Clear all DTC's with a  engine scan tool (diagnostic   trouble codes)
•   Start the engine and observe the MIL, if it does not illuminate   continue to next step (malfunction   inductor lamp or  check   engine light)
•  Drive the vehicle while trying to maintain a constant throttle   position as it accelerates up through all four gears. If the transmission is   shifting properly, it should be in 4th gear by the time you reach 45 to 50 mph   on level ground. Repeat this procedure from a standing start 3 to 5 times. Rescan   the PCM for trouble codes, if none appear the problem could have been a onetime   occurrence. If  trouble   codes have returned repair as needed and recheck system.
  Tips: Never allow little noises go unattended, a small noise can cause  a large noise and transmission failure. Avoid overloading a vehicle or towing beyond  capacity this can cause premature transmission failure.

Black Smoke

Black smoke is caused by too much fuel being processed inside your car's engine and then released from the tailpipe of your car. Malfunctions in fuel delivery or internal system leaks will cause black smoke to come from the tailpipe. Before fuel injection became available in automobiles in the mid 1980's, the carburetor was the main fuel and air mixer in most vehicles. A carburetor was a simple device that supplied the engine with proper fuel to air mixtures. Carburetors performed two operations 1. meter air flow 2. deliver the correct amount of fuel to air mixture. This mix could be kept even during the wide range of extra factors associated with an engine such as high temperature, cold starting, hot starting, idling and acceleration.

Fuel Injector Cut Away

The primary difference between a carburetor and a fuel injection system is that the fuel injection system atomizes fuel by pushing it through a small nozzle under pressure, while a carburetor utilizes vacuum created by air flow into the intake manifold. Airflow in an injection engine is controlled by the throttle body; fuel is distributed directly in each cylinder. This creates better fuel control, lower emissions and faster acceleration. The process of measuring the amount of fuel a fuel injector is dispersing is determined by the ECM (engine control module). The fuel injection system has several parts: the mass airflow sensor or map sensor, throttle body, throttle position sensor, idle control valve, fuel pump, fuel pressure regulator, fuel lines
, and oxygen sensors.

Cause of Black Smoke
Black smoke is caused when the mix of fuel and air becomes un-balanced. Normal mixture is 14.5 parts air to1 part fuel. When the fuel to air mixtures change because of a malfunction the mixture can go as high as 14.5 to 2 or 3, two to three times the proper amount. The black smoke is the excess fuel generated from the rich mixture and can be cause by one of the following:

* Plugged Air Filter
* Shorted or stuck fuel injector
* Failed fuel pressure regulator
* Vacuum leak
* Shorted ECM Sensor

Trouble Shoot Black Smoke
Check Engine Light
If the check engine light is illuminated the ECM has detected a malfunction that could be causing the problem, scan the ECM to retrieve trouble codes and repair as needed.

Preventive Maintenance
To check your car's mixture you will need to use a gas analyzer to test your exhaust gases. This will measure the carbon monoxide, hydrocarbon, nitrogen oxide and oxygen content of your exhaust. During a normal smog inspection the fuel/air mixture is tested and a report generated. When a tune up is performed the spark plug end insulator can tell you whether you have a lean or rich mixture. Brownish grey is the desired color and confirms proper mixture. Black and sooty means the mixture is too rich while white to light grey confirms a lean mixture.

Fuel injection systems rely on pressurized fuel to operate. Maintaining this pressure is mandatory for the system to function properly. Replace your fuel filter with every tune up to keep your injection system operating properly.

Alternator and Charging System

A battery is needed to power the operating system of your car. Once the vehicle is running an alternator that is driven by the engine charges the battery. While in operation the alternator creates electricity, about 13.6 to 14.3 volts, and recharges the battery to its original state of charge. The alternator is one of the hardest working electrical components in your vehicle. When your vehicle is running the alternator is busy creating electricity to provide the engine and the car accessories with needed power. When the car is not running and your battery is severely discharged some electrical components such as alarms or other memory retaining items may still operate or operate poorly. Typically, these components are designed to operate properly at 12 volts; if the system voltage is low it can cause erratic symptoms.

Common Problems and Solutions
When jump-started a severely discharged battery can cause the alternator to overload and internally fail. If this occurs replace or charge the battery before replacing the alternator. This will help prevent a second alternator failure. Most vehicles use a multi-ribbed belt connected to the engine to rotate the armature inside the alternator. If the belt fails it should be replaced immediately. Belt tension should be taught. If it isn't, check the belt tensioner, it may need to be replaced or the incorrect size belt may have been installed. Either of these conditions can cause the vehicle to stall and not restart.

Additionally, problems can occur if the alternator is overcharging the system. Some symptoms of overcharging include a swollen or seeping battery, both headlight bulbs failing at the same time, and other electrical component problems. To perform an alternator system check for this condition use a voltmeter on both positive and negative terminals while the engine is idling. If the voltmeter reading is over 15 volts this is an indication of an overcharging alternator. The alternator should be replaced with an OE (original equipment) unit. While an inferior rebuilt alternator is often much cheaper, it can fail prematurely causing another costly replacement.

The most common alternator problem is "undercharging." This condition is often accompanied by symptoms such as a low state of charge on the battery, poor or erratic performance from electrical components and dim headlights and other lighting systems. The first symptom of an undercharging alternator is a slow cranking engine. The next symptom is a "machine gun" sound when the engine is cranked as the system voltage drops below normal operating levels. In order to correct this problem a replacement alternator must be installed after the battery has been replaced or charged.

Maintenance
To ensure that your alternator lasts as long as possible there are several things you can do. Be sure all battery connections are tight and both terminals are clean. This should be inspected periodically regardless of when the battery was changed as even new batteries can have problems and be defective. While the engine is off, visually inspect the alternator belt and replace the belt if cracks or tears are observed.