Technica Service Training Goba Fundamentas Curricuum Training TF0004S Automatic Transmission Student Information FCS-300-REF CG7970/S en /00
Copyright 00 Ford Motor Company
Introduction Preface Goba fundamentas training overview The goa of the Goba Fundamentas Training is to provide students with a common knowedge base of the theory and operation of automotive systems and components. The Goba Fundamentas Training Curricuum (FCS-303-REF) consists of nine sef-study books. A brief isting of the topics covered in each of the sef-study books appears beow. Shop Practices (FCS-30-REF) expains how to prepare for work and describes procedures for ifting materias and vehices, handing substances safey, and performing potentiay hazardous activities (such as weding). Understanding hazard abes, using protective equipment, the importance of environmenta poicy, and using technica resources are aso covered. Brake Systems (FCS-30-REF) describes the function and operation of drum brakes, disc brakes, master cyinder and brake ines, power-assist brakes, and anti-ock braking systems. Steering and Suspension Systems (FCS-396-REF) describes the function and operation of the powerassisted steering system, tires and whees, the suspension system, and steering aignment. Cimate Contro (FCS-398-REF) expains the theories behind cimate contro systems, such as heat transfer and the reationship of temperature to pressure. The sef-study aso describes the function and operation of the refrigeration systems, the air distribution system, the ventiation system, and the eectrica contro system. Eectrica Systems (FCS-397-REF) expains the theories reated to eectricity, incuding the characteristics of eectricity and basic circuits. The sef-study aso describes the function and operation of common automotive eectrica and eectronic devices. Manua Transmission and Drivetrain (FCS-399-REF) expains the theory and operation of gears. The sef-study aso describes the function and operation of the drivetrain, the cutch, manua transmissions and transaxes, the driveshaft, the rear axe and differentia, the transfer case, and the 4x4 system. Automatic Transmissions (FCS-300-REF) expains the function and operation of the transmission and transaxe, the mechanica system, the hydrauic contro system, the eectronic contro system, and the transaxe fina drive. The sef-study aso describes the theory behind automatic transmissions incuding mechanica powerfow and eectro-hydrauic operation. Engine Operation (FCS-395-REF) expains the four-stroke process and the function and operation of the engine bock assemby and the vave train. Aso described are the ubrication system, the intake air system, the exhaust system, and the cooing system. Diese engine function and operation are covered aso. Engine Performance (FCS-394-REF) expains the combustion process and the resuting emissions. The sef-study book aso describes the function and operation of the powertrain contro system, the fue injection system, the ignition system, emissions contro devices, the forced induction systems, and diese engine fue injection. Read Engine Operation before competing Engine Performance. To order curricuum or individua sef-study books, contact Hem Inc. To Free: -800-78-4356 (8:00 am 6:00 pm EST) Mai: 430 Hamiton Ave., Highand Park, MI 4803 USA Internet: www.heminc.com (4 hours a day, 7 days a week) Service Training
Contents Introduction Introduction... Preface... Goba fundamentas training overview... Contents... Lesson Automatic transmissions... 5 Genera... 5 Objectives... 5 At a gance... 6 Automatic transmissions... 6 Theory... 7 Torque converter... 7 Gear train... 8 Powerfow... 9 Basic powerfow... 9 Lesson Torque converter...0 Genera... 0 Objectives... 0 At a gance... Torque converter overview... Components... Three-eement converter... Operation... 6 Fuid fow reversa... 6 Torque mutipication... 6 Lock-up... 9 Hydrauic and mechanica couping... 9 Centrifuga cutch... 0 Hydrauicay appied torque converter cutch... Lesson 3 Hydrauic principes... 5 Genera... 5 Objectives... 5 At a gance... 6 Hydrauics overview... 6 Oi pump... 8 Oi pump purpose... 8 Typica pump operation... 30 Pressure reguation... 3 Fuid... 35 Fuid fow... 35 Fow contro... 36 Vave body... 4 Fuid circuit diagrams... 4 Contro vaves... 44 Governor vave... 44 Throtte vave circuit... 45 Vacuum moduator... 46 Throtte vave... 48 Service Training
Introduction Contents Lesson 4 Appy devices... 50 Genera... 50 Objectives... 50 At a gance... 5 Cutches and bands... 5 Cutches... 5 Mutipe-disc cutch... 5 Bands... 60 Bands and servos... 60 Accumuators and moduators... 6 Purpose of accumuators and moduators... 6 Lesson 5 Panetary gear sets...63 Genera... 63 Objectives... 63 At a gance... 64 Purpose of a panetary gear set... 64 Operation... 65 Reduction... 65 Direct drive... 66 Reverse... 67 Types... 68 Simpe and compound gear trains... 68 Simpson gear train... 69 Powerfow... 69 Operation... 78 Advantages of panetary gear sets... 78 Compound gear train... 79 Lesson 6 Transaxe... 80 Genera... 80 Objectives... 80 At a gance... 8 Transaxe theory... 8 Systems... 83 Chain drive system... 83 Fina drive... 84 Purpose... 84 Components... 85 Ider gear type... 85 Chain drive type... 87 Differentia assemby... 88 Operation whees straight... 88 Operation whees turned... 89 Service Training 3
Contents Introduction Lesson 7 Eectronic contros...9 Genera... 9 Objectives... 9 At a gance... 9 Contro systems... 9 System inputs... 93 Contro modue theory... 93 Contro modue inputs... 94 System outputs... 00 Contro system outputs... 00 Soenoid operations... 04 Lesson 8 Diagnosis... 08 Genera... 08 Objective... 08 At a gance... 09 Symptom-to-system-to-component-to-cause diagnostic process... 09 Workshop iterature... 09 List of abbreviations... 0 4 Service Training
Lesson Automatic transmissions Genera Objectives Upon competion of this esson, you wi be abe to: Identify the primary purpose of the transmission. Describe the functions of the three major transmission systems: torque converter, gear train, and hydrauic contro system. Describe powerfow through the transmission. Service Training 5
At a gance Lesson Automatic transmissions Automatic transmissions The purpose of a transmission is to modify the engine s rotationa force, or torque, and transfer it to the vehice s drive axe. Through its torque converter and gear sets, the transmission provides the necessary force to move the vehice. The transmission aso aows the vehice to be operated in reverse. This section introduces the basic operating principes of automatic transmissions. Automatic transmissions have many design variations. However, they are a simiar in that they use three basic systems: Torque converter Gear train Hydrauic contro system 6Service Training
Lesson Automatic transmissions Theory Torque converter 3 ATX00-A/VF Engine crankshaft Fex pate 3 Torque converter The torque converter provides a fuid couping that inks the engine to the transmission gear train. (In a fuid couping, the spinning motion of the transmission fuid transfers rotationa force from the crankshaft to the transmission.) At ow speeds, the torque converter mutipies the engine torque when operating as a fuid couping. When equipped with a torque converter cutch, the converter aso provides direct mechanica (ock-up) drive under certain operating conditions. Service Training 7
Theory Lesson Automatic transmissions Gear train 3 4 ATX003-C/VF Typica simpe gear set Ring gear Sun gear 3 Panet carrier 4 Panet gears (pinions) A typica gear train incudes the input shaft; panetary gear set, and output shaft. Two different types of gear trains are used. A simpe, or Simpson, gear train and a compound or Ravigneaux gear train. A panetary gear set has three members: the ring gear, the sun gear, and the pinion (or panet ) gears. These members are driven or hed by friction (hydrauic) cutches, one-way (mechanica) cutches, and brake bands. Hydrauic contro system The hydrauic contro system contros the cutches and bands needed to provide gear ratios and shift from one gear to another. This system aso distributes oi to the torque converter and the transmission s ubrication and cooing systems. The hydrauic contro system consists of a sump (oi pan), oi pump, vaves to reguate pressure and redirect fow, and pistons to actuate the friction cutches or bands. The gear train provides the reduction gear ratios, as we as direct drive, overdrive, and reverse. 8 Service Training
Lesson Automatic transmissions Powerfow Basic powerfow 3 4 5 6 7 8 0 9 ATX004-A/VF Typica powerfow Engine crankshaft Transmission turbine 3 Torque converter impeer 4 Oi pump 5 Input shaft 6 Friction cutch hub or drum 7 Panetary gear set 8 Output shaft 9 Vave body 0 Sump Power fows from the engine crankshaft through The input shaft is connected to a friction cutch the torque converter, which turns the transmission hub or drum. input shaft. The panetary gear set transfers power from the input shaft to the output shaft. The cutch drum transfers power to the panetary gear set. A gear set member can be couped to The torque converter impeer, which is attached to (driven by) the input shaft through a friction the engine, spins at engine speed and drives the oi cutch. In some cases, a gear set member is hed to pump. the case by a friction cutch, one-way cutch, or The oi pump draws automatic transmission fuid band. from the sump and sends pressurized oi to the The output member of the panetary gear set vave body and torque converter. transfers engine power to the output shaft. The pressurized fuid inside the converter forms a fuid couping, which turns the transmission turbine and input shaft. Service Training 9
Genera Lesson Torque converter Objectives Upon competion of this esson, you wi be abe to: Identify the major components in a torque converter and expain their functions. Describe how the impeer and turbine provide a fuid couping between the engine and transmission. Describe the operation of the stator and its one-way cutch. Expain how the stator, impeer, and turbine mutipy torque. Describe the purpose of a ock-up converter. Expain how a centrifuga converter cutch provides a direct mechanica ink between the engine and transmission. Expain how a hydrauicay appied piston cutch provides a direct mechanica ink between the engine and transmission. 0 Service Training
Lesson Torque converter At a gance Torque converter overview The rotationa force, or torque, of the engine is transferred to the automatic transmission through the torque converter. This section describes how the torque converter assemby components provide a fuid couping, mutipy torque at ow speeds, and estabish a direct mechanica ink to the engine at high speeds. The torque converter provides a fuid couping between the engine crankshaft and the transmission. A fex pate is boted to the rear of the crankshaft, and the torque converter is boted to the fex pate. The automatic transmission fuid (ATF) in the torque converter transfers the spinning motion of the crankshaft to the transmission input shaft. Whenever the engine is running, the torque converter is spinning. A simpe torque converter has three basic eements: an impeer, a stator and a turbine. Most modern torque converters aso have a cutch to ock the torque converter at the proper vehice operating conditions. Service Training
Components Lesson Torque converter Three-eement converter With the engine running and the torque converter empty of fuid, the input shaft wi not turn. However, when the torque converter is fied with fuid, the shaft wi not ony turn, it wi turn with enough force to drive the transmission interna components, which drive the vehice. Therefore, the fuid in the torque converter makes the connection between the engine and the transmission. 3 Based on the simpe three-eement converter, there is no mechanica connection between the engine-driven portion of the converter and the transmission input shaft. Ony the fuid in the torque converter coupes the engine to the input shaft. The paragraphs on the foowing pages describe each component of the torque converter and expain how the hydrauic couping is accompished. ATX006-A/VF Basic torque converter Fuid Turbine 3 Impeer Service Training
Lesson Torque converter Components Impeer If you are famiiar with the design of vehice water pumps, then you aready know what an impeer is. The impeer on a water pump is a round component with vanes that turns on a shaft. When the engine is running, the spinning impeer vanes force cooant to circuate through the cooant passages and radiator. The impeer vanes on a torque converter work in a simiar way. The spinning impeer forces hydrauic fuid to circuate via centrifuga force. The fuid is carried in a circuar motion by the vanes, and, as speed increases, the fuid fows away from the center of the impeer. As the fuid fows outward, the vanes carry it toward the upper edge of the impeer. As impeer speed increases, the fuid gains enough momentum to fow off the edges of the vanes and out of the impeer. The fuid comes out of the impeer with enough force to drive the transmission input shaft if the force is propery directed. 3 4 ATX007-B/VF Impeer operation Impeer shaft Impeer vane 3 Spinning impeer 4 Cooant thrown outward by centrifuga force Service Training 3
Components Lesson Torque converter Three-eement converter (continued) Turbine 3 5 4 ATX009-A/VF Torque converter expoded view Turbine Stator 3 Impeer The turbine in a torque converter is simiar in construction to the impeer. That is, the turbine is a round part with vanes, or bades. This construction makes sense when you consider that the turbine catches the fuid thrown off by the impeer. As the fuid is thrown off the impeer, the bades on the turbine capture it, forcing the fuid to the center of the turbine. This force turns the turbine before the fuid fows back through the center of the turbine to the impeer. 4 Turbine bades 5 Stator one-way cutch The force of the fuid striking the turbine bades is reated to engine speed. The faster the crankshaft rotates, the more force the fuid transfers from the impeer to the turbine. When the engine is iding, the fuid does not have enough force to turn the turbine against the hoding abiity of the brakes. The fuid is merey circuated from the impeer to the turbine, and back again. The fuid eaves the impeer in a cockwise direction and returns from the turbine in a countercockwise direction. 4 Service Training
Lesson Torque converter Components Stator (reactor) The stator, or reactor, is positioned between the turbine and impeer. The purpose of the stator is to change the direction of fuid fow as it moves from the center of the turbine to the center of the impeer. The fuid fows from the impeer to the turbine in a cockwise direction. However, as the fuid fows through the turbine, its direction is reversed to a countercockwise direction. If the fuid were aowed to return to the impeer in a countercockwise direction, it woud enter the impeer as an opposing fuid fow, which woud reduce the pumping efficiency of the impeer. The impeer woud have to spend part of the rotationa force, or torque, it receives from the engine to redirect the fuid fow. When the stator redirects the fuid to enter the impeer in a cockwise direction, no torque is wasted. In fact, the redirected fuid actuay heps push the impeer, thus mutipying torque. The cutch assemby has an inner and outer race, or ring, with the two races separated by spring-oaded roers. The inner race is mounted on a spined, or grooved, stator support, which extends from the transmission into the torque converter. Because the inner race is spined to the stator support, it is fixed and cannot turn. The outer race is paced over the inner race. The inner and outer race are separated by spring-oaded roers. The roers are positioned against the ow end of ramps machined into the outer race. When the springs are instaed, the roers are hed against the ramps. The roers, ramps, and races aow the outer race to turn in ony one direction. When the stator turns cockwise, each roer moves down the ramp against the spring, aowing the stator to turn. If the stator is rotated in the opposite direction, the spring pushes each roer up the ramp, where it becomes wedged between the two races. With the roers wedged, the stator is ocked to the inner race and cannot rotate. The stator consists of severa bades attached to a hub which is mounted on a one-way cutch. Service Training 5
Operation Lesson Torque converter Fuid fow reversa The countercockwise fow of fuid eaving the turbine passes through the stator bades before reaching the impeer. The curvature of the stator bades reverses the direction of the fuid. The change of direction aows the fuid to enter the impeer and join the fuid fowing aong its bades. The first advantage of a stator is that engine torque is not wasted by having the impeer redirect the fow. A second advantage is that the fuid enters the impeer in a direction that appies a heping push aong the impeer bades. ATX008-A/VF Reversing fuid fow Turbine Impeer Torque mutipication The infuence of the stator means that the fuid entering the impeer is aready in motion; the fuid does not have to be acceerated from a standsti. The fuid moves into the bades, where its momentum is acceerated. The acceeration whips the fuid through the impeer and throws it toward the turbine with greaty increased force. Through this efficient management of the fuid, the turbine torque actuay becomes greater than the engine s torque. In effect, the torque is mutipied. Torque mutipication by the stator is ony possibe when there is a great difference in speed between the impeer and the turbine. The greater the speed difference between the two, the greater the torque mutipication. 6Service Training
Lesson Torque converter Operation Torque mutipication 3 4 5 ATX00-A/VF Stator one-way cutch operation Turbine Impeer 3 Roers wedged between ramp and inner race (cutch ock-up) The stator s one-way cutch pays an important roe in mutipying torque. The fuid circuating between the impeer and the turbine is caed vortex fow. This fow exists ony when there is a difference in rotationa speed between the impeer and turbine. The greatest speed difference between these two components occurs when a vehice first acceerates from a stop. At this point, the impeer is spinning, but the turbine is not. Because of the great difference in speed, vortex fow and torque mutipication are at maximum. The vortex fow passing through the stator bades tries to turn the stator countercockwise. When this happens, the cutch roers move down the ramps and ock the stator to its support. As the vehice acceerates, the turbine graduay gains speed in reation to the impeer. Eventuay, the turbine speeds up to the point where the fuid begins to fow in one direction (cockwise). 4 Direction of force on stator 5 Vortex f ow As centrifuga force reduces vortex fow, torque mutipication is aso reduced. Finay, when the turbine s speed reaches about 90 percent of the impeer s speed, the torque converter reaches couping phase. In this phase, the torque converter simpy transmits engine torque through the fuid couping to the transmission input shaft. Couping does not necessariy occur at a specific road speed. For exampe, a vehice may be moving at a steady speed with the torque converter couped to the transmission. If the driver suddeny acceerates to pass another vehice, the higher engine rotation increases the speed of the impeer, causing it to turn faster than the turbine. With a significant speed difference between the impeer and the turbine, torque mutipication (and vortex fow) again occurs, unti the turbine catches up with the speed of the impeer. Service Training 7
Operation Lesson Torque converter Torque mutipication (continued) 3 4 ATX0-A/VF Stator one-way cutch operation Turbine Impeer 3 Roers moved away from ramp (cutch unocked) 4 Cockwise direction of force on stator As turbine speed increases and vortex fow decreases, the rotationa force acting on the stator is reversed. The cutch roers move away from their ramps, unocking the cutch and aowing the stator to turn freey (cockwise). The direction of the fuid striking the stator bades aso changes. Instead of fowing against the front of the stator bades, the fuid strikes the rear of the bades. If the cutch did not reease the stator, its bades woud generate turbuence in the fow, which woud greaty reduce the torque converter s efficiency. 8 Service Training
Lesson Torque converter Lock-up Hydrauic and mechanica couping Because the torque converter acks a direct mechanica ink to the engine, it oses some engine torque to fuid sippage. The speeds and oads imposed on the fuid cause the impeer and turbine bades to shear, or sip, through the fuid to a certain degree. This fuid sippage causes some inefficiency, especiay at higher vehice speeds. The engine can run faster than the turbine or output shaft, thus wasting fue. To eiminate this inefficiency, many torque converters provide a direct mechanica ink (caed ock-up) between the engine and transmission. At ock-up, the turbine and impeer turn at exacty the same speed. There is no fuid sippage, which heps to reduce heat buid-up. A ock-up converter is one of the most common ways of providing this mechanica ink. A ock-up converter mechanicay inks the turbine to the converter cover at various operating speeds, depending on vehice mode and driving conditions. The cover is mechanicay boted to the engine. At ock-up, the converter cover drives the turbine. The hydrauic ink is eiminated, and the engine and turbine are mechanicay ocked together, directy driving the transmission input shaft. A ock-up converter requires a cutch to engage and disengage the mechanica ink between the engine and the torque converter cover. Two major types of converter cutches are the centrifuga cutch and the hydrauicay appied torque converter cutch. The centrifuga type converter cutch was mainy used before 990. The hydrauicay appied cutch is mainy used in today s vehices. Service Training 9
Lock-up Lesson Torque converter Centrifuga cutch ATX005-B/VF Torque converter assemby Cover Torque converter cutch 3 Impeer assemby A centrifuga cutch is spined to the turbine by a one-way cutch. As vehice speed increases, the hydrauicay driven turbine and the ock-up cutch spined to it turn with increasing speed. The centrifuga force on the cutch shoes increases as the cutch assemby turns faster and faster. 4 Stator 5 Turbine When the turbine and ock-up cutch are turning fast enough, centrifuga force causes the cutch shoes to move outward unti they contact the inside surface of the converter cover. The face of each shoe grabs the cover and ocks it to the turbine. 0 Service Training
Lesson Torque converter Lock-up As vehice speed drops, turbine speed and centrifuga force are reduced. The return springs retract the cutch shoes, the cover is reeased, and the turbine again becomes hydrauicay driven. A one-way cutch drives the cutch assemby. With the cutch engaged, the driver may reease the acceerator peda sighty, aowing the vehice to coast. This aows the engine and input shaft to turn at different speeds. The damper assemby one-way cutch ensures smooth operation of the torque converter. The dampener springs aso contribute to smooth operation. These springs absorb engine vibrations and cushion the shoes as they engage the converter cover. When torque demand during acceeration exceeds the hoding abiity of the friction shoes, some sip occurs. This sippage reduces torsiona vibration during higher engine oad. The friction shoes cannot reease during coasting because centrifuga force hods them against the cover. Instead, the damper one-way cutch reeases so the input shaft can turn faster than engine speed. When the driver acceerates, the damper one-way cutch again ocks the turbine to the cutch and damper assemby. Service Training
Lock-up Lesson Torque converter Hydrauicay appied torque converter cutch 3 4 5 ATX0-A/VF Converter cutch reeased Rear chamber TCC 3 Front chamber 4 Converter pressure 5 Cutch contro vave Another method of connecting the engine and transmission directy is to use a torque converter cutch (TCC) with torsiona dampening springs attached to the hub. The hub assemby is spined to the input shaft or turbine assemby. Service Training
Lesson Torque converter Lock-up Hydrauic cutch reeased Signas from the contro modue contro the appication and reease of the hydrauic converter cutch. The contro modue appies and reeases the hydrauic cutch by turning the converter cutch soenoid on or off. A soenoid is a type of eectric switch that incudes a wire coi. When current is appied, the coi is magnetized. The magnetic fied moves a rod that opens and coses a hydrauic passage. Hydrauic pressure is appied to the area between the converter cover and the cutch piston pate. A converter feed circuit in the vave body provides the hydrauic pressure. When the converter cutch soenoid is not activated by the contro modue, the soenoid remains open. Line pressure beeds through the soenoid. The fuid is routed through the converter front chamber, between the TCC and the converter cover. Service Training 3
Operation Lesson Torque converter Hydrauicay appied torque converter cutch (continued) Hydrauic cutch engaged 3 4 5 6 7 ATX03-B/VF Converter cutch engaged Rear chamber Converter cover 3 TCC 4 Front chamber The converter cutch engages ony when the contro modue energizes the converter cutch soenoid. The soenoid seas the beed passage, aowing ine pressure to buid in the circuit. Fuid is routed to the rear chamber, and the fuid drains from the front chamber. 5 Drain to sump 6 Converter appy pressure 7 Cutch contro vave Hydrauic force pushes the TCC piston against the converter cover. This couping directy transfers the engine torque through the damper assemby to the transmission input shaft. Since the impeer and turbine are turning at the same speed, torque mutipication is canceed, and the converter is in ock-up. 4 Service Training
Lesson 3 Hydrauic principes Genera Objectives Upon competion of this esson, you wi be abe to: Identify the components in a transmission oi pump and describe how they provide fuid fow and pressure. Describe the three operating stages of the pump. Describe how the pressure reguator vave operates to maintain a desired system pressure. Describe how pressurized fuid transfers motion among moving parts. Describe a spoo vave with mutipe ands and expain how it opens and coses various hydrauic passages. Describe how the governor circuit operates to send road speed information to the hydrauic main contro. Describe how the throtte vave (TV) can be connected to the engine to read throtte position or engine performance. Service Training 5
At a gance Lesson 3 Hydrauic principes Hydrauics overview Hydrauics is the science that deas with the behavior of fuids. In the automatic transmission, we are 3 specificay concerned with the behavior of fuid under pressure. This section describes the basic hydrauic principes at work in an automatic transmission. When pressurized iquid is propery controed, it can 3 be used to transmit motion. Fuid under pressure can be used to transfer motion from one piston to another. When the appying piston moves within the cyinder, its motion is transmitted through the fuid to the output piston, which moves the same distance as the appying piston. Of course, a mechanica ink coud be used to perform this simpe task, but using fuid has a very big advantage: the two pistons do not have to be encosed in the same cyinder. In fact, they can be widey separated in individua cyinders. A that is needed is a connecting tube to confine the fuid as it moves from cyinder to cyinder. ATX04-A/VF Singe hydrauic cyinder Appying piston Fuid 3 Output piston 6Service Training
Lesson 3 Hydrauic principes At a gance The appying piston transfers its motion through the fuid to the output piston. 3 3 ATX05-A/VF Appy and output cyinders Appying piston Fuid 3 Output piston The abiity of a fuid to transmit motion comes from its incompressibiity. That is, when a fuid is squeezed, or compressed, its voume does not shrink. So, for exampe, it woud take 9,09 Kg (3 tons) to compress 6.45 cubic centimeters (one cubic inch) of water by 0 percent. 3 ATX06-A/VF Compressing hydrauics 9,09 Kg (3 tons) 6.45 cubic centimeters (one cubic inch of water) 3 Compressed 0 percent Service Training 7
Oi pump Lesson 3 Hydrauic principes Oi pump purpose Because an automatic transmission requires pressurized fuid, it must have a pressure source an oi pump. The oi pump is driven by the engine and provides a source of fuid fow. Types of pumps 3 Three styes of pumps are used in most automatic transmissions: Rotary type Gear type 5 4 Vane type A pumps have an inet and outet port. The inet port is attached to the transmission oi fiter, which is submerged in the oi pan. Oi is pushed into the inet port by atmospheric pressure and by the ow pressure created by the rotating rotor, gear, or vane in the pump. The outet (or discharge) port eads to the vave body. ATX07-B/VF Gear type pump Driven gear Crescent 3 Drive gear 4 Fuid squeezed out 5 Inet (ow pressure) 8 Service Training
Lesson 3 Hydrauic principes Oi pump Rotary type A rotary type pump uses an inner rotor and an outer rotor to create a ow pressure. As fuid is drawn into the pump, it is squeezed between the rotor obes, which carry the fuid around the pump housing to the outet port. Vane type A vane type pump uses centrifuga force to push fuid through the pump. As the fuid enters the inet port, it is picked up by the rapidy spinning vanes. Centrifuga force sings the fuid off the end of the vanes and through the outet port. Gear type A gear type pump uses a arge gear with interna teeth (caed the driven gear) mounted over the drive gear on the hub. This arger gear is off center, so the teeth on the two gears ony partiay mesh. As the gears turn, a progressivey wider gap is formed between the gear teeth. The gap creates a ow pressure, which sucks the fuid into the pump. Because this gap must be fied with fuid, another component, caed the crescent, is added to the gear assemby. The crescent prevents the fuid from eaking back to the inet port. As the gap between the gear teeth narrows, the fuid is squeezed out between the teeth and forced through the outet port. Service Training 9
Oi pump Lesson 3 Hydrauic principes Typica pump operation The inet of the transmission oi pump is connected to a sump, or oi pan, in the bottom of the transmission case. As the fuid is drawn up from the sump, it passes through a fiter, which removes partices and debris. 3 Fuid enters the pump inet because air pressure pushes down on the surface of the oi. At sea eve, air pressure is about.0 bar (4.7 psi). Air pressure cannot actuay push the fuid up through the strainer into the pump. The pump first has to create a ow pressure, or void, at the inet port opening. Then atmospheric pressure can push the fuid into the pump to fi the void. 7 8 9 4 5 In a gear type pump, the pump creates a ow pressure through the action of the gear teeth. The teeth are tighty meshed, but as they rotate, they begin to separate. This separation creates a ow pressure between the gear teeth, and atmospheric pressure pushes the fuid in to fi this void. Once in the pump, the fuid is trapped between the gear teeth, which carry it around the pump housing toward the outet port. As the gear teeth approach the outet, the gap between the gear teeth begins to narrow. The fuid cannot eak back toward the inet port because the crescent bocks its path. The gap continues narrowing unti the gear teeth begin to mesh. At this point, the fuid is squeezed between the teeth unti it reaches the outet port. From the outet, the fuid is discharged into the transmission hydrauic system. 6 ATX08-A/VF Gear pump operation Crescent Driven gear 3 Drive gear 4 Fuid squeezed out 5 Pump outet 6 Oi sump fiter 7 Sump (fuid pan) 8 Pump inet 9 Low pressure 30 Service Training
Lesson 3 Hydrauic principes Oi pump Pressure reguation Transmission oi pumps are cassified as positive dispacement or variabe dispacement pumps. A vane type pump is a variabe dispacement pump. This means that it suppies a fixed quantity of oi output once the engine reaches a specific speed. Feedback pressure from the vave body return circuit keeps the vane type pump from producing more output than is required. This feature heps conserve engine power by reducing the amount of horsepower required to drive the pump. 3 Rotary and gear type pumps are positive dispacement pumps. This means that the pump must force out a the fuid that enters it. There is no other escape for the fuid except the outet port. A positive dispacement pump continues to pump out fuid even if the pressure on the outet side is extremey high. In fact, if the outet port is bocked, a positive dispacement pump continues to operate unti it eventuay stas from extremey high pressure. To prevent sta, a positive dispacement pump must have a method of rerouting the fuid fow if pressure becomes too high. As pump pressure buids, a pressure reguator vave opens and coses to maintain system pressure at a safe eve. Movement of the pressure reguator vave is controed by a caibrated spring. The spring tension determines the opening pressure of the reguator vave. 6 ATX09 -A/VF Pressure reguator circuit To system Pressure reguator vave 3 Spring 4 Pump 5 Screen 6 Sump 5 4 Service Training 3
Oi pump Lesson 3 Hydrauic principes Pressure reguation (continued) Three stages of operation The pressure reguator vave has three distinct stages of operation: Fiing the ines Converter suppy Fiing the ines Immediatey after the vehice is started, the ines are fied with fuid. At this stage, there is itte resistance to fow in the system, so pressure does not buid up. The spring beow the reguator vave hods it in the up (or cosed) position. Sump suppy 3 Service Training
Lesson 3 Hydrauic principes Oi pump Converter suppy As pressure begins to rise in the system, the reguator vave is forced down against the spring, and another port is uncovered. Fuid from the pump fows through this port into the torque converter circuit. Since the 3 torque converter is kept under constant pressure, another fuid outet is required to prevent excessive pressure buid-up. 6 4 5 ATX00-A/VF Torque converter suppy circuit To torque converter To system 3 Pressure reguator vave 4 Pump 5 Screen 6 Sump Service Training 33
Oi pump Lesson 3 Hydrauic principes Pressure reguation (continued) Sump suppy Pressure continues to buid, and the reguator vave is forced down further against the spring. Another oi port is uncovered. This port connects to the sump in the bottom of the transmission case. A excess oi is returned to the sump, where it can be recircuated through the pump inet. This fina stage is the norma operating condition when the engine is running. Baanced vave Once the pressure reguator vave has reached stage 3, the pressure in the main contro system is reguated by baancing the pressure against the force of the vave spring. The spring contros the pressure, and the vave adjusts itsef automaticay so that the spring force acting upward is equa to the hydrauic pressure acting downward. 4 3 If the pressure drops, the spring moves the vave up and cuts off part of the fow to the sump (and to the torque converter, if necessary) to maintain the reguated pressure. This vave is caed a baanced vave, and the pressure it reguates is caed contro or ine pressure. Line pressure can aso be controed by an eectronic soenoid. ATX0 -A/VF Sump suppy circuit Pressure reguator vave Pump 3 Screen 4 Sump 34 Service Training
Lesson 3 Hydrauic principes Fuid Fuid fow In an automatic transmission, fuid is routed through passages and bores. Athough many of these are ocated in the case and pump housing, most bores and passages are in a master fow contro device caed the vave body. Fuid fow through these passages is controed by either a singe vave or a series of vaves working in combination. With the exception of two vaves, a the contro vaves in the vave body operate automaticay to direct the fuid to perform certain functions. For exampe, the shift from first to second gear, caed the - shift, is a specific hydrauic function. When this shift happens, the fuid fows through specific bores, passages, and vaves. This fuid fow is caed an oi circuit. An automatic transmission has an oi circuit for each hydrauic function. In fact, the pressure reguator vave described in the previous section is an oi circuit that contros pump pressure. When you study an oi circuit, you are ooking at a schematic, or kind of map, that shows the fuid path and vaves for performing a specific function. Service Training 35
Fuid Lesson 3 Hydrauic principes Fow contro 3 4 5 6 ATX0-A/VF 8 7 Fow contro circuit vave cosed Pressure reguator vave Vave bore 3 Vave cosed 4 Piston at top of stroke 5 Cyinder 6 Exit port 7 Rod 8 Pump To demonstrate basic principes of fow contro, we wi examine a hypothetica vave bore. This bore is connected to the fuid fow from the pressure reguator vave. With the engine running, fuid fows from the pressure reguator circuit to the vave bore and stops. It cannot pass through the bore because the vave is bocking the inet port. Within this bore is a singe-and vave connected to a rod that extends through one end of the bore. (A and is the round seaing surface of the vave.) On the sides of the bore are two ports: an inet port joined to the fuid from the pressure reguator, and an exit port joined to a passage eading to a cyinder. Within this cyinder is a piston at the top of its stroke. 36Service Training
Lesson 3 Hydrauic principes Fuid 3 4 ATX03-B/VF 5 Fow contro circuit vave open Pressure reguator vave Vave open 3 Pressurized fuid in cyinder If the vave is manuay opened, fuid fows into the inet port, through the bore, and out the exit port on its way to the cyinder. 4 Piston 5 Pump When the fuid reaches the cyinder, it pushes on the piston surface, forcing it to move the ength of the cyinder bore. The force generated by the pump is transferred to the piston. Service Training 37
Fuid Lesson 3 Hydrauic principes Fow contro (continued) ATX05-B/VF 4 3 Fow contro circuit fuid pushed back by spring Pressure reguator vave Vave cosed The oi circuit is functiona, but it acks one important feature: automatic reset. When the pressure is reeased, the piston does not automaticay return to the top of the bore, ready for another stroke. To make the piston reset automaticay, a spring is added behind the piston. With the vave cosed and the fuid fow stopped, the spring tension shoud push the piston back to the top of the cyinder. However, the spring cannot move the piston as ong as pressurized fuid is trapped in the cyinder circuit. The spring cannot move the piston unti the fuid is drained from the cyinder. 3 Exhaust port 4 Pump Now the vave can open the inet port from the pump, as we as the exit port to the cyinder. At the same time, the vave seas the exhaust port to the sump, preventing any pressure oss. When the vave coses the inet port, it aso opens the cyinder passage to the exhaust port. The fuid drains out of the exhaust port as the spring pushes the piston back through the cyinder. To provide an outet for draining the pressurized fuid, the circuit must be reworked. Adding an exhaust passage to the sump and offsetting the cyinder passage aows the inet port to be seaed without trapping fuid in the cyinder. 38 Service Training
Lesson 3 Hydrauic principes Fuid Spoo vave The spoo vave has two or more ands, or seaing areas, connected by a rod, giving the vave a spoo shape. The area between the ands aows fuid to fow through the vave bore. When a spoo vave moves, the ands open and cose various ports to direct fuid fow. For exampe, the upper and is at the top of the bore, opening the pump inet. The ower and seas the exhaust port, aowing fuid to fow through the center of the cyinder bore. 3 4 6 3 5 ATX06-B/VF Spoo vave circuit Pressure reguator vave Spoo vave 3 Vave and (seaing surface) 4 To cyinder 5 To sump 6 Pump Service Training 39
Fuid Lesson 3 Hydrauic principes Fow contro (continued) The spoo vave coses the pump inet port and opens the exhaust port. This reeases pressurized fuid from the cyinder and aows it to drain through the exhaust port back to the sump. The vaves described in this section iustrate the hydrauic principes that appy to the contro vaves in an automatic transmission. Pressure can be used to move: vaves against spring pressure. 3 vaves back and forth in a bore. pistons in a cyinder. A of these operations occur in an automatic transmission to contro fuid fow and maintain ine pressure. 5 4 ATX07-B/VF Spoo vave circuit Pressure reguator vave Spoo vave 3 From cyinder 4 To sump 5 Pump 40 Service Training
Lesson 3 Hydrauic principes Fuid Vave body 3 4 5 6 9 8 ATX08-A/VF 7 Typica vave body Vave body Pressure reguator vave 3 Spring seat 4 Spring 5 Spring 6 Retaining cip 7 Bore pug 8 Line pressure boost vave 9 Worm tracks The vave body is the master fow contro component for an automatic transmission. It contains a compex pattern of passages caed worm tracks, as we as severa bores containing mutipe-and vaves. Each passage, bore, and vave forms an oi circuit for a specific function. Service Training 4
Fuid Lesson 3 Hydrauic principes Fuid circuit diagrams Using a fow diagram, you can trace an oi circuit and determine exacty which vaves and passages are used to accompish a specific transmission function. 4 3 ATX09-A/VF Fow diagram pressure reguator vave Pressure reguator vave Springs 3 Screen 4 Pump 4 Service Training
Lesson 3 Hydrauic principes Fuid 3 4 ATX030-B/VF Fow diagram manua vave Pressure reguator vave Manua vave If you foow the pump fow away from the pressure reguator, you find the manua vave. This vave is connected through a mechanica inkage to the shift seector in the vehice s passenger compartment. The manua vave moves in or out of its bore depending on the position of the shift seector (for exampe: P, R, or D ). 3 Trapped fuid 4 Vave ands The ine pressure stops at the manua vave because it is trapped between two ands. In other gear ranges, the vave ands move to redirect the fow to various vaves, cutches, and servos. Service Training 43
Contro vaves Lesson 3 Hydrauic principes Governor vave 3 4 5 8 7 ATX03-A/VF 0 9 6 Typica governor vave Primary weight Exhaust to sump 3 Governor pressure out 4 Line pressure in 5 Inner and When the driver moves the shift seector ever to one of the drive positions, another important oi circuit becomes active. The governor vave circuit is used to time the shifts in an automatic transmission. The governor vave takes the ine pressure directed from the manua vave and transforms it into a pressure signa. This signa tes the shift contro vaves how fast the vehice is moving. (The shift contro vaves direct the fuid fow that shifts gears, for exampe from first to second gear, or from third to second gear.) In most cases, the governor vave is mounted on the output shaft, where it rotates with the shaft. In frontwhee drive vehices, the governor is usuay driven by gears at the fina drive. 6 Seeve 7 Governor vave 8 Outer and 9 Vave spring 0 Secondary weight The governor assemby consists of a separate sma vave body with three passages: one for ine pressure, one for governor pressure, and one for exhaust to the sump. When the vehice is stopped, the fuid directed to the governor is bocked. As the vehice begins to move, the governor rotates, and centrifuga force causes the weights to move outward. Depending on the rotation speed, the outward movement of the weights pushes the vave, aowing reguated pressure to enter the governor vave, where it is directed to the shift contro vaves. On eectronic controed transmissions, the governor is repaced by a soenoid controed by the contro modue. 44 Service Training
Lesson 3 Hydrauic principes Contro vaves Throtte vave circuit To propery time a shift, the automatic transmission has to know more than just road speed. It aso has to know what oad the engine is under. Load refers to the amount of force the engine must overcome to generate power. For exampe, a vehice going up a steep hi at 64 km/h (40 mph) paces a heavier oad on the engine than the same vehice going down the hi at 40 mies per hour. In addition, running the air conditioning system at fu power can aso pace a heavy oad on the engine. In an automatic transmission, the throtte vave (TV) circuit determines the engine oad, transforms it into a pressure signa, and directs the signa to the shift contro vaves. Governor pressure coud be used to signa a shifts, but the shifts woud aways occur at the same road speed and woud not vary according to engine oad. For exampe, during rapid acceeration, the engine is under a heavy oad, and the transmission shoud remain in first gear onger to take advantage of the extra puing power avaiabe in the ower gear ratio. If the governor circuit aone were controing the shifts, the transmission woud shift into second at a pre-determined road speed, and acceeration woud sow dramaticay. With the throtte vave and governor circuits working together, the transmission matches gear shifts to engine speed and oad. Throtte pressure aso modifies ine pressure. At ide, pressure is minima to reduce shift shock when the gears engage. At fu throtte, pressure is maximum so that cutches are squeezed tighty, preventing sippage. Two types of throtte vave circuits are used in most vehices. The first type reads engine oad via a vacuum moduator. Vacuum is negative pressure generated by the engine when the pistons move down in their cyinders during the intake stroke. Vacuum decreases with the oad paced on the engine. The second type of throtte vave circuit determines engine oad through a mechanica inkage to the acceerator peda. On eectronic controed transmissions, the throtte vaue is repaced by soenoids and controed by the contro modue. Service Training 45
Contro vaves Lesson 3 Hydrauic principes Vacuum moduator 4 ATX03-A/VF 3 Typica vacuum moduator vave Main case To engine vacuum 3 Vacuum moduator 4 Pin When vacuum is used to determine oad, a vacuum moduator is mounted on the vave body case. 46Service Training
Lesson 3 Hydrauic principes Contro vaves 3 6 5 4 ATX033-A/VF Vacuum moduator vave operation Throtte pressure Diaphragm 3 Manifod vacuum The vacuum moduator contains two chambers separated by a spring-oaded diaphragm. A hose or tube connects one side of the diaphragm to the engine s intake manifod. The other side of the diaphragm is connected to a rod that extends into the vave body case. 4 To engine vacuum 5 Atmospheric pressure 6 Throtte vave (case) As engine oad varies, so does the vacuum in the intake manifod, and the diaphragm moves in and out with these variations. The movement of the diaphragm is transferred to the rod, which moves a vave in the throtte vave circuit. This vave constanty aters the pressure in the throtte vave circuit, which redirects pressure to the shift contro vaves. Service Training 47
Contro vaves Lesson 3 Hydrauic principes Throtte vave 3 5 4 ATX034-A/VF Typica throtte vave Throtte cam Spring 3 Throtte vave In a throtte vave circuit controed by mechanica inkage, a throtte cam transfers the motion of the acceerator peda to the throtte vave. The throtte cam is mechanicay inked to the acceerator peda. When the peda is pressed, the cam turns, moving the spring. The spring pushes the throtte vave to the right, opening the ine pressure passage. This increases pressure to the throtte moduator vave. 4 Line pressure (from pressure reguator vave) 5 Throtte pressure (to throtte pressure moduator vave) As throtte pressure rises, it causes the spring to compress, moving the throtte vave back to the eft. The ine pressure port is cosed, and throtte pressure drains. When throtte pressure fas, the spring again pushes the throtte vave to the right, opening the ine pressure port and increasing throtte pressure. By repeating this cyce, the throtte vave constanty adjusts throtte pressure. When the acceerator peda is reeased, the cam turns in the opposite direction, reeasing the spring. The throtte vave moves back to the eft, cosing the ine pressure port, which decreases throtte pressure. 48 Service Training
Lesson 3 Hydrauic principes Contro vaves Throtte and governor pressures Pressure from two separate circuits infuences shift timing: throtte pressure, which is based on engine oad; and governor pressure, which is based on road speed. Each of these circuits receives ine pressure from the pump and modifies it into a pressure signa. The modified pressures deveoped in the throtte and governor circuits exert force on the shift contro vaves, just as fuid forced the piston to move in the sampe circuit described previousy in this section. Working with ine pressure, the modified pressures from the governor and throtte circuits contro the vaves that automaticay shift gears to match engine oad and road speed. The vaves in the vave body contro fuid fow through circuits that connect ine pressure to the various bands and cutches that contro shifting. Service Training 49
Genera Lesson 4 Appy devices Objectives Upon competion of this esson, you wi be abe to: Identify the components in a hydrauic mutipe-disc cutch and describe their functions. Identify the components of a band and servo assemby and describe their functions. Describe the purpose of accumuator and moduator vaves in the hydrauic contro system. 50 Service Training
Lesson 4 Appy devices At a gance Cutches and bands When an automatic transmission shifts gears, various gear train components must rotate, whie other components are prevented from rotating. This section describes how cutches and bands drive and hod gear train members in an automatic transmission. Cutches and bands perform opposite but compementary functions in an automatic transmission. Cutches drive gear train members, forcing them to rotate. Bands, on the other hand, hod gear train members, preventing them from rotating. Band overview Instead of connecting two rotating parts, a band hods a component and prevents it from rotating. When a band is hydrauicay appied, it camps around a drum and keeps it from turning. The band is anchored to the transmission case, and its camping force is strong enough to prevent the drum from rotating. Cutch overview The cutch in an automatic transmission is simiar to a manua cutch in that it connects and disconnects the engine from the transmission. If you turn the input shaft on an automatic transmission with the cutch reeased, the output shaft does not turn. But if you appy the cutch and turn the input shaft, the output shaft turns because the cutch forms a mechanica ink between the two shafts. Service Training 5