247Service.AUDI A2 - Engine and GearboxDesign and FunctionSelf-study programme 247For internal use only.2ContentsPage OverviewEngine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 l - TDI (55 kW) AMF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 l - 16 V (55 kW) AUA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gearbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 5 6EngineDesign and function of the 1.4 l - 16 V engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . System overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lambda control of the Euro-On-Board Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . Functional overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 16 21 24GearboxOverview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gearbox design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Double synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gear shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actuators and sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 28 30 35 39 42New The self-study programme will provide you with information on design and functions. It is not intended as a workshop manual! For maintenance and repairs please refer to the current technical literature.Attention Note3OverviewEngine1.4 l - TDI (55 kW) AMF70 63 56 49 42 35 28 21 14 7 0 0 1000 2000 3000 4000 5000 6000 200 180 160 140 120 100 80 60 40 20 0Power output [kW]SSP247_072 SSP247_071Technical data Engine code: Design: Capacity: Power output: Torque: Bore: Stroke: Compression: Weight: AMF Turbocharged threecylinder in-line engine 1422 cm3 55 kW (75 PS) at 4000 rpm 195 Nm at 2200 rpm 79.5 mm 95.5 mm 19.5 : 1 130 kg Firing order: Mixture induction: Turbocharger: 1-2-3 Direct injection with pump-nozzle unit Garrett GT 12 turbocharger with wastegateExhaust emissions Oxidising catalytic control: converter and exhaust gas recirculation Exhaust emissions standard:EU 3 Fuel: Diesel, cetane rating at least 49 CN, RMEPlease refer to SSP 223 for the design and function of the 1.4 l TDI pumpnozzle engine.The engine code and engine number are located on the front engine/gearbox flange.SSP247_026 4Torque [Nm]1.4 l - 16 V (55 kW) AUA70 63 200 180 160Power output [kW]56 49 42 35 28 21 14 7 0120 100 80 60 40 20 0 0 1000 2000 3000 4000 5000 6000SSP247_001SSP247_002Technical data Engine code: Design: Capacity: Power output: Torque: Bore: Stroke: Compression: Weight: AUA Four cylinder in-line engine Petrol engine 1390 cm3 55 kW (75 PS) at 5000 rpm 126 Nm at 3800 rpm 76.5 mm 75.6 mm 10.5 : 1 90 kg Ignition system: Firing order: Mixture induction: 1-3-4-2 Electronic, sequential multipoint injection, adaptive idlecontrol, deceleration fuel cut-off Distributorless ignition system with static highvoltage distribution, longlife spark plugsExhaust emissions control: 3-way catalytic converter, 2 heated lambda probes, activated charcoal filter Exhaust emissions standard: EU 4 Fuel: Petrol, unleaded, 95 RON– Lambda control with probes upstream and downstream of the catalytic converter – Electric exhaust gas recirculation valve – Valve actuation via rocker armsSSP247_069 5Torque [Nm]140OverviewGearbox02T gearbox 02J gearboxSSP247_073SSP247_074The 02T gearbox is an extremely lightweight two-shaft gearbox. The parts of the housing are made of magnesium. It is designed to transmit torque values of up to 200 Nm.The familiar 02J gearbox is used in the A2 1.4 l TDI, for torques up to 250 Nm.Both gearboxes are actuated via gear selector cables and gate selector cables.SSP247_075SSP247_0766EngineDesign and function of the 1.4 l - 16 V engineThe cylinder block is made of die-cast aluminium. The required stiffness is achieved by pronounced ribbing, and is further reinforced by the crankshaft bearing blocks.The cylinder liners are made of cast iron. They are cast into the crankcase and can be reworked. The webs with the cast cylinder liners have a thickness of 5.5 mm.G12 is the only approved coolant additive. As well as preventing frost damage on the aluminium housing, it prevents the formation of lime deposits and damage due to corrosion in the coolant channels.SSP247_003The crankshaft is made of cast iron and is equipped with four balancer weights. Despite this weight saving, the crankshaft has the same running characteristics as crankshafts with eight balancer weights. The bearing blocks support the internal stiffness of the aluminium cylinder block.SSP247_004The crankshaft must not be loosened or removed. If the bearing cap bolts are released then the internal structure of the bearing blocks in the cylinder blocks slackens and causes them to warp. The bearing clearance is then reduced.If the bearing cap bolts are released then the complete crankcase with crankshaft needs to be replaced. It is not possible to measure the bearing clearance of the crankshaft using standard workshop equipment.7EngineCamshaft drive The two camshafts are driven by two toothed belts. Due to the narrow width of the cylinder head, the toothed belt drive is divided into a main drive and a coupled drive.Toothed belt - main drive Toothed belt coupled driveIdler roller Tensioning roller for coupled drive Idler rollerMain driveCoolant pump belt pulleyThe main toothed belt drive transmits the drive from the crankshaft to the coolant pump and the intake camshaft. An automatic tensioning roller and two idler rollers prevent the toothed belt from vibrating.Main drive tensioning roller Intake camshaftCrankshaft toothed belt sprocket SSP247_005Coupled driveThe toothed belt of the coupled drive is toothed belt located directly behind the toothed belt of the sprocket main drive, outside the camshaft housing. The coupled drive transmits the drive from the intake camshaft via the toothed belt to the exhaust camshaft. Here again an automatic tensioning roller prevents the toothed belt from vibrating.Coupled drive Exhaust camshaft toothed belt sprocketSSP247_006Guide holesGuide holes are provided in the camshaft housing and at the camshaft toothed belt sprockets for assembly and for adjusting the valve timing. The two toothed belt sprockets are secured with a special tool. Please refer to the repair manual for more details.SSP247_007 8Valve gear The intake camshaft and the exhaust camshaft run on bearings in the camshaft housing. At the same time the camshaft housing also acts as the cylinder head cover. The camshafts run on 3 bearings and are pushed into the camshaft housing. The axial clearance is limited by the camshaft housing and the blanking plugs.Intake camshaftBlanking capExhaust camshaftCamshaft housing SSP247_008 Exhaust camshaftCylinder headThe liquid sealer must not be applied too liberally, as excess material can enter the oil bores and cause engine damage.Cylinder headValve actuation In this generation of engines, the valve actuation and the valve clearance compensation are provided by means of a rocker arm with a hydraulic support element. Advantages – reduced friction – less weight to move DesignHydraulic support element Roller bearing of cam rollerSSP247_009 CamshaftCam roller Rocker arm ValveThe rocker arm consists of a pressed metal lever and a cam roller with roller bearing. It is clipped in at the support element and laid onto the valve.SSP247_010 9EngineHydraulic support element Design The support element consists of: – a piston – a cylinder and – a piston spring It is connected to the engine oil circuit. A small ball with a spring forms a one-way valve in the lower oil chamber.Oil channel Piston with bore CylinderUpper oil chamber Lower oil chamberPiston spring SSP247_011Function during valve clearance compensation In the event of excessive valve clearance the piston is pushed out of the cylinder by the piston spring until the cam roller lies up against the cam. While it is being pushed out the oil pressure in the lower chamber reduces. The one-way valve opens and oil flows in. Once the pressure difference between the lower and upper oil chamber has been equalised the one-way valve closes.One-way valveValve clearanceSSP247_012Valve lift When the cam runs onto the cam roller the pressure in the lower oil chamber increases. The trapped oil cannot be compressed, which means that the piston cannot be pushed any further into the cylinder. The support element becomes a rigid element which acts as a support for the rocker arm. The corresponding valve opens.SSP247_01310Lubrication is provided via the hydraulic support element. The rocker arm has a bore through which oil is sprayed onto the cam roller.Oil Cam rollerOil bore in the support elementOil channel in the cylinder headSSP247_014Function during valve actuationCamThe support element acts as a pivoting point for the motion of the rocker arm. The cam runs on the cam roller and presses the rocker arm downwards. The valve is then actuated via the rocker arm. The lever arm between the cam roller and the support element is shorter than between the valve and the support element. This means that a relatively small cam can achieve a large valve lift.Cam rollerRocker armThe hydraulic support elements cannot be checked.SSP247_01511EngineElectric exhaust gas recirculation valveEGR valve N121Pressure equalisationSupply line to intake manifoldExhaust manifoldSSP247_016EGR valve N121 is electrically controlled and actuated directly by engine control unit J537. The valve is flanged directly onto the cylinder head and directly connected to the exhaust duct of cylinder no. 4 by means of a channel in the cylinder head.A stainless steel pipe connects the valve with the intake manifold. The high temperatures caused by the exhaust gases are transferred to the cylinder head and cooled by the coolant flowing through.12Functional diagramAir cleaner Intake manifoldJ537N121G212t °C n 1/min p MPaSupply line to intake manifoldEngine load SSP247_017Even in normal operation of the engine a certain amount of residual gas leaks from the combustion chamber into the intake manifold when the valves are rocking.. In the subsequent induction process a proportion of the residual gas is then drawn in with the fresh mixture (internal exhaust gas recirculation). Up to a certain degree the residual gas (exhaust gas) can have a positive effect on reducing the amount of nitrogen oxides in the exhaust, and it can help to convert energy more efficiently (reduced fuel consumption). The additional exhaust gas recirculation helps to reduce NOx emissions (nitrogen oxides) further and to lower fuel consumption. To do this, a certain amount of exhaust gas is taken and fed back to the intake air via EGR valve N121. This is called “external” exhaust gas recirculation.In order to optimise the distribution of recirculated exhaust gas and induced fresh air, the exhaust gas emerges into the fresh air flow directly under the middle of the throttle valve, at two holes positioned at right angles to the intake air flow. EGR valve N121 is actuated by engine control unit J537 according to a defined map. It takes information such as engine speed, engine load, air pressure and coolant temperature into account. EGR potentiometer G212 informs the engine control unit of the cross-section of the opening. With the exhaust gas recirculation active the amount of gas that can be recirculated is limited to 18 % of the intake air quantity. There is no exhaust gas recirculation in idle, in overrun or during engine warm-up up to 35 oC13EngineFunctionPotentiometerThe EGR valve terminates (zero-current process) the recirculation of exhaust gases to the intake manifold. It is switched on from a coolant temperature of 35 oC. When it is actuated, the valve is opened with a defined duty cycle. The input information includes – information about the engine speed – information about the load status of the engine – coolant temperature – air pressure A potentiometer is located in the valve head. This potentiometer detects the opening cross-section of the valve, which is passed back as a return message to the engine control unit. The opening cross-section is then used to control the voltage of the coil in the valve according to the map. A direct connection to ambient air pressure is provided via the air cleaner to allow for pressure equalisation in the valve during the different control phases.AnchorCoilExhaust gas from enginePressure equalisation via air cleanerValveTo intake manifold SSP247_018Electrical circuit Diagnostics The valve has diagnostic capabilities. The following are stored in the fault memory: – Zero point shift – Maximum opening – Maximum path It is also detected if a valve is sticking. G212 J537 N121SSP247_019EGR potentiometer Control unit for 4LV Frequency valve for exhaust gas recirculation14The fuel pump located inside the fuel tank pumps fuel through the fuel filter to the injectors.Gravity valveOperating breather containerFuel pump G6 Activated charcoal filterDistribution rail Fuel filterSolenoid valve for ACF system N80Fuel pressure regulator Injectors N30 … N33SSP247_020 Intake manifoldThe A2 is equipped with a safety fuel shut-off system for the event of a crash, as described in SSP 207.15EngineOverview of systemIntake manifold pressure sender G71 with Intake air temperature sender G42 Control unit for 4LV J537Engine speed sender G28 Versions I and IIHall sender G40Knock sensor I G61Lambda probe upstream of catalytic converter G39 with Heater for lambda probe Z19 Lambda probe downstream of catalytic converter G130 with Heater for lambda probe Z29 Coolant temperature sender G2/G62Throttle valve control part J338 with Throttle valve drive G186 (electric throttle operation) Angle sender 1/2 for throttle valve drive G187/G188 Diagnostic connectionAccelerator pedal module with accelerator pedal position sender G79/G185Brake light switch F/F47 Auxiliary input signals A/C compressor Air conditioner (engine speed increase) Tank fill level*; crash signal; CCS switch; DF signal; vehicle speed signal from combi-processor J218 16Ignition transformer N152Injectors N30, N31, N32, N33Fuel pump relay J17 Fuel pump G6Control unit for ESP J104Solenoid valve I for ACF system N80TEMPOFFAir conditioner control and display unit E87Throttle valve drive G186 with throttle valve positioner V60EGR valve N121 Combi-processor in dash panel insert J218Heating resistor N79 (crankcase breather) Sender for steering angle G85 Auxiliary output signals Engine speed signal* A/C compressor SSP247_021* discontinued as of CAN compatible combi-processor J21817EngineEngine speed sender G28 The sender is a combined speed sender and reference mark sender. Two different sealing flange systems and sender versions are in use.Engine speed sender G28Crankshaft Elastomer gasketSender wheel Sealing flange Crankshaft Gasket Sender wheelSender wheelSSP247_078Sealing flangeSealing is provided at the crankshaft.18J448Engine speed sender G28G28SSP247_080CrankshaftSender wheelSealing flange Sender wheelCrankshaftSender wheelSSP247_079Sealing flangeApplication of the signal The signal from the engine speed sender is used to detect the engine speed and the exact position of the crankshaft. The engine control unit uses this information to determine the timing of injection and ignition.The effect of a signal failure The engine control unit switches to emergency running mode if the engine speed sensor fails. The control unit then calculates the engine speed and camshaft position from information provided by camshaft position sender G163. The maximum engine speed is lowered in order to protect the engine. It is still possible to restart the engine.19EngineThe Hall sender G40 is located at the camshaft housing above the intake camshaft. Three teeth are cast onto the intake camshaft, where they are scanned by the Hall sender.Application of the signal The signal is used together with the signal from the engine speed sender to detect ignition TDC on cylinder no. 1. This information is required for the cylinderselective knock control and the sequential fuel injection. J537The effect of a signal failure In the event of sender failure the engine continues to run and can also be restarted. The engine control unit goes into emergency running mode. The fuel injection then switches from sequential to parallel mode.G40SSP247_029Hall sender G40SSP247_030Intake camshaft with cast-on sender wheel Blanking cover Camshaft housing20Lambda control of the Euro-On-Board-DiagnosisThe new broadband lambda probe is used as a pre-cat probe in conjunction with the EOBD. An almost linear current increase is used for the output of the lambda value. As a result the lambda value can be measured over the entire engine speed range. Function With the broadband lambda probe, the lambda value is calculated from a change in current rather than a change in voltage. However, the physical processes are the same. Broadband lambda probeI = current SSP247_022Planar lambda probeThe familiar planar lambda probe is used as the post-cat probe. The measuring range fluctuates erratically around the value lambda = 1 and is sufficient for monitoring purposes.U = voltage Planar lambda probe SSP247_023Broadband lambda probeSSP247_083 21EngineBroadband lambda probe7This probe uses two electrodes to generate a voltage relating to the varying oxygen content of the exhaust gas.5The voltage at the electrodes is kept constant. This process is achieved by means of a miniature pump (pump cell), which supplies the electrode on the exhaust side with enough oxygen to keep the voltage between the two electrodes at a constant value of 450 mV. The engine control unit converts the current consumption of the pump into a lambda value. 1 2 3 4 5 6 7 8 996 83 2 1 4 SSP247_024Fresh air Probe voltage Engine control unit Electrodes Exhaust gas Miniature pump (pump cell) Pump current Measuring range Diffusion channelExhaust gas 61 5 4 3 2 SSP247_0251 2 3 4 5 622Oxygen pump cell Nernst cell (two-point probe) Probe heater Fresh air (reference air) Measuring range Diffusion channelIf the fuel/air mixture becomes too rich then the oxygen content of the exhaust gas drops. The pump cell pumps less oxygen into the measuring area and the voltage rises at the electrodes. In this case more oxygen escapes through the diffusion channel than is pumped by the pump cell.SSP247_027The pump cell has to increase its pumping rate to make the oxygen content in the outer air chamber rise. This regulates the electrode voltage back to the value of 450 mV, and the engine control unit then converts the current consumption of the pump into a lambda value. If the air/fuel mixture is too lean then this function is reversed.SSP247_028The pumping effect of the pump cell is a purely physical process. A positive voltage at the pump cell attracts negative oxygen ions through the ceramic, which is permeable to oxygen.The linear lambda probe and the engine control unit form a system together. The lambda probe must match the engine control unit.23EngineFunctional diagramKey 1.4 l - 16 V (55 kW) AUA Components E45 E227 F F36 F47 G6 G28 G39 CCS switch Button for cruise control system Brake light switch Clutch pedal switch Brake pedal switch Fuel pump Engine speed sender Lambda probe upstream of catalytic converter G40 Hall sender G42 Intake air temperature sender G61 Knock sensor I G62 Coolant temperature sender G71 Intake manifold pressure sender G79 Accelerator pedal position sender G130 Lambda probe downstream of catalytic converter G185 Accelerator pedal position sender 2 G186 Throttle valve drive (electric throttle operation) G187 Angle sender 1 for throttle valve drive (electric throttle operation) G188 Angle sender 2 for throttle valve drive (electric throttle operation) G212 EGR potentiometer J17 Fuel pump relay J218 Combi-processor in dash panel insert J338 Throttle valve control part J537 Control unit for 4LV M9/10 Bulb for left/right brake light N30 … 33 Injectors, cylinders 1 … 4 N79 Heating resistor (crankcase breather) N80 Solenoid valve for ACF system N121 Frequency valve for exhaust gas recirculation N152 Ignition transformer P Spark plug connector Q Spark plugs Z19 Heater for lambda probe Z29 Heater for lambda probe 1, downstream of catalytic converter Colour coding = input signal = output signal = battery positive = earth = CAN-BUS = bi-directional = diagnostic connectionAuxiliary signals 1 2 Crash signal, airbag control unit Terminal 50 signal, ignition starter switch Alternator terminal DF Vehicle speed signal (from combi-processor J218) A/C compressor (engine speed increase) Tank fill level* TD signal* A/C compressor3 456 7 8CAN-BUS H = CAN-BUS L =}Databus drivexConnection within the functional diagram* discontinued for CAN compatible combi-processor J21824+15+30+30S20 20AS31 10A3 J17S18 20AS45 15AS19 20AS30 10AX X G39 Z19 G130 Z29FF36N79 1 2MG6N30N31N32N33N80λλM CAN - H CAN - L 3 4 5 6 7 8 F47J537XN152J338+M+oE45I IV II IIIE227G185G79G186G187G188N121 X G212 G40 G42 G71 G28G62G61Q P31inoutGearboxOverviewThe 5-speed manual gearbox 02TSSP247_032The 02T gearbox is an extremely lightweight two-shaft gearbox. The parts of the housing are made of magnesium. The gearbox can transmit torques of up to 200 Nm.This gearbox is used across the range in conjunction with numerous engines. Therefore it was important to design the gear wheel transmission ratios and the final drive ratio as flexibly as possible.26Engine/gearbox combinations Manual 5-speed gearbox Gearbox code Engine allocation z2 Final drive 1st gear 2nd gear 3rd gear 4th gear 5th gear Reverse gear Speedometer Gear oil fill capacity Gear oil specification Gear oil change Clutch mechanism 66 38 44 43 40 39 35 24 Ratio i = No. of teeth on driven wheel z2 No. of teeth on driving wheel z1 EYX 1.4 l/55 kW z1 17 11 21 31 39 48 24 11 i 3.882 3.455 2.095 1.387 1.026 0.813 3.182 z2 61 34 36 34 34 34 36 18 EWO 1.4 l/55 kW z1 18 09 17 25 35 45 20 09 i 3.389 3.778 2.118 1.360 0.971 0.756 3.600electronic 1.9 litres G50 SAE 75 W 90 (synthetic oil) Filled for service life hydraulicThe code letters of the gearbox are also given on the vehicle data plates.27GearboxHousingThe gearbox housing consists of 2 magnesium parts (gearbox housing, clutch housing). A cover closes off the gearbox housing to the outside. The parts of the gearbox housing are made of magnesium in support of its lightweight design principles. This measure alone has led to a weight reduction of 2.5 kg compared to the conventional aluminium design..Mounting points for engine/ gearbox mountings Gearbox housingGearbox housing coverClutch housingSSP247_03328The gearbox has a modular design concept.Key assemblies: Clutch release lever This module contains the release lever, the release bearing and the guide sleeve.SSP247_034Selector shaft with selector mechanism cover This module contains all of the locking elements, spring elements and guide elements of the gearshift mechanism.SSP247_035Internal selector mechanism (shift mechanism) with the selector forks and the selector plates.SSP247_036Bearing support with the two grooved ball bearings and the pre-assembled input and output shafts.SSP247_056 29GearboxGearbox designReverse idler gearGearbox housing cover1st/2nd gear are double-synchronised. All the other forward gears are single-synchronised. The teeth of the sliding gears and the gear wheels are helical-cut and constantly meshed.Gearbox housingAll of the sliding gears run on needle roller bearings. The sliding gears are distributed between the input shaft and the output shaft 1st and 2nd gear is selected on the output shaft, 3rd, 4th and 5th gears on the input shaft.30The reverse gear is a straight-cut gear. The reversal of the direction of rotation on the output shaft is effected with a reverse idler gear, which sits on a separate shaft in the gearbox housing and is shifted between the input shaft and the output shaft. Torque is transmitted to the differential via the output gear wheel on the output shaft to the final drive gear wheel.Clutch release leverInput shaftOutput shaftClutch housingFinal drive gear wheelA wide range of special tools is available for all repair work involving the removal and installation of bearings, bushes, oil seals etc. Please refer to the notes in the repair manual.SSP247_038 31GearboxInput shaft The input shaft is designed in the classic fixed/loose mounting style. It runs on – a cylindrical roller bearing (loose) in the clutch housing and – a grooved ball bearing (fixed) which is seated in a bearing unit in the gearbox housing.The input shaft has a deep-drilled hole in order to save weight.SSP247_039 3rd gear sliding gear 1st gear teeth 2nd gear teeth 4th gear sliding gear Deep-drilled hole for weight reduction5th gear sliding gearSSP247_040 Bearing unit with grooved ball bearing Reverse gear teeth Cylindrical roller bearingThe teeth for 1st gear, 2nd gear and reverse gear are permanently connected to the input shaft. The needle roller bearing for the 5th gear runs on a sleeve on the shaft side. The needle roller bearings of the 3rd and 4th gears run directly on the input shaft.The synchro-hubs for the 3rd/4th gear and the 5th gear are attached via fine teeth. Circlips keep them in position.The deep-drilled hole and the hollow bore in the output shaft have resulted in a weight reduction of approx. 1 kg.32Output shaft The output shaft is also designed in the classic fixed/loose mounting style. Just like the input shaft it runs on – a cylindrical roller bearing (loose) in the clutch housing and – a grooved ball bearing (fixed) which sits together with the input shaft in the bearing unit in the gearbox housing. The output shaft has a hollow bore to reduce weight.SSP247_041 1st gear sliding gear 5th gear wheel 2nd gear sliding gear 3rd gear wheel 4th gear wheelDrilled hole for weight reductionSSP247_042 Bearing unit with grooved ball bearing Gear teeth to final drive gear wheelCylindrical roller bearingThe gear wheels for the 3rd, 4th and 5th gears and the 1st/2nd gear synchro-hub are attached via fine teeth. Circlips keep them in position.The sliding gears of the 1st and 2nd gears run on needle roller bearings on the output shaft.The grooved ball bearings for the input and the output shafts should only be replaced as a joint bearing assembly.33GearboxDifferential The differential (with flange shafts for the final drive) forms an assembly with the manual gearbox. It runs on two frictionally optimised taper roller bearings in the gearbox and the clutch housing. Sealing rings (different sizes for the left and right hand sides) seal the housing to the outside. The final drive crown wheel is riveted to the differential housing and paired with the output shaft (to lower transmission noise). The sender wheel for the speedometer is an integral part of the differential housing.SSP247_043The differential needs to be adjusted if any components are replaced that affect the play of the taper roller bearings. This is done with a shim in the clutch housing. Please refer to the repair manual for further details.Output shaft Final drive gear wheel Clutch housing Gearbox housing Differential housing ShimSSP247_044Taper roller bearingTaper roller bearing Segments for detection of rotational speedFlange shaft34Double synchronisation1st and 2nd gear are double-synchronised. A second synchroniser ring (inner) is used with an outer ring for this double synchronisation.SSP247_045The double synchronisation improves the smoothness of the gear change from 3rd gear down to 2nd and from 2nd gear down to 1st. Thanks to the almost doubling in size of the tapered frictional surface area, the effectiveness of the synchronisation is improved by approx. 50%, and the gear change effort is reduced by roughly a half.SSP247_046 1st gear sliding gear 2nd gear sliding gearLocking collar with synchro-hub for 1st and 2nd gearThe double synchronisation consists of: – a synchroniser ring (inner) – an outer ring – a synchroniser ring (outer). Synchronisation takes place via the two synchroniser rings and the outer ring.SSP247_047 Sliding gear Synchroniser ring (inner) Outer ring Synchroniser ring (outer) 35GearboxPower flowSSP247_048SSP247_049SSP247_051SSP247_05036SSP247_052SSP247_053Power flow in the gearbox The engine torque is transmitted to the gearbox via the input shaft. Depending on the selected gear, the torque is then transmitted to the appropriate pair of gears on the output shaft, and from here to the final drive gear wheel and the differential. The torque and rotational speed then act on the drive wheels according to the settings of the gearshift mechanism.SSP247_05437GearboxBearing support The grooved roller bearings are not mounted directly onto the gearbox housing, and instead sit in a separate bearing support.Bearing support Input shaft SSP247_055The complete package of shafts and gear wheels for the input shaft and the output shaft is pre-assembled outside the gearbox housing in the bearing support, and can then be easily inserted into the gearbox housing. A disc shape is used to secure the grooved roller bearings in installation position. The disc shape is welded to the bearing support. The grooved roller bearings have their own radial oil seals on both sides that keep any abraded particles suspended in the gear oil away from the bearings. The bearing support is pressed into the gearbox housing with its collar in the shape of a pair of glasses, and is then attached to the gearbox housing with six bolts. The bearing support is replaced as a complete unit with the two grooved roller bearings after repairs. This is done every time the unit is dismantled. Please also refer to the notes in the repair manual.SSP247_056Output shaft38Gear selectionInternal shift mechanism The gear selection movements come into the gearbox from above. The selector shaft is guided in the selector mechanism cover. For gate selection movements it is moved in an axial direction. Two spring-loaded balls prevent the selector shaft from twisting out of the selected gear position.Selector shaftSSP247_057Shift mechanism cover Ball (not visible) Angular contact ball bearing Selector segmentThe bearings for the selector forks for 1st/2nd gear and 3rd/4th gear are angular contact ball bearings. They help to improve the smoothness of gear changes. The selector fork for the 5th gear has a friction bearing. The selector forks and selector plates are loosely coupled to each other. When a gear is selected the selector shaft moves the selector plate with its fixed selector finger, and the selector plate in turn moves the selector fork. The selector segments of the selector forks sit in the locking collar of the corresponding pair of gear wheels.Selector plate3rd/4th gear selector fork Reverse gear selector fork 5th gear selector fork 1st/2nd gear selector fork 39 SSP247_058GearboxAdjusting the selector cables Both the gearshift mechanism housing and the gearshift mechanism cover have been fitted with auxiliary devices that make adjustments to the selector cables a lot easier. No measuring operations or templates for marking positions are required.Gear selector cableGate selector cableThe adjustment always begins with the gearbox in neutral:– Loosen the cables: The securing mechanism on the gear selector cable and the gate selector cable is pulled forwards as far as its stop and then twisted to the left to lock it. The length of the cables can now be adjusted, which is performed automatically when the selector shaft and selector lever are positioned as follows.SSP247_059– Lock the selector shaft: A bracket is attached to the gearshift mechanism cover which can be used to secure the selector shaft in a pre-defined position. To do this, press the selector shaft downwards by hand into the 1st/2nd gear gate, and while pressing down turn the adjusting bracket in the direction of the arrow and press it against the selector shaft. It engages and locks the selector shaft in this position.BracketSSP247_06040R 1 3 5Position of the gear lever during the adjustment process2 4SSP247_061 Locating lugT10027 Guide pin– Lock the gear lever: The gear lever is moved into in the 1st/2nd gear gate with the gearbox in neutral. The gear lever has a fixed locating lug. Guide pin T10027 is inserted through the hole in the lug into the bore in the gearshift mechanism housing which lies underneath.SSP247_062– Securing the cables: Now the securing mechanism on the gate selector cable and the gear selector cable can be twisted back to the right. The spring presses the securing mechanism into the selected position and secures it. Now release the bracket again and take out the guide pin. The gear lever should now be in the 3rd/ 4th gear gate when the gearbox is in neutral.SSP247_063 41GearboxSensors and actuatorsVehicle speed display The speedometer is driven without any mechanical intermediate stages. The information required for the vehicle speed is taken as a rotational speed directly from the differential housing by vehicle speed sender G22. The differential housing has reference markings for this purpose, 7 raised segments and 7 indentations.Reference markings on the differential housing SSP247_064 Sender for speedometer G22The sender operates in accordance with the Hall sender principle. The PWM signal (pulse width modulated) is sent to the combiprocessor in dash panel insert J218.SSP247_065Electrical circuit D +15 G21 G22 J218 Ignition starter switch, terminal 15 Speedometer Vehicle speed sender Combi-processor in the dash panel insertG21J218D +15G2231SSP247_06642Reversing light switch F4 The reversing light switch is bolted to the side of the gearbox housing. When reverse gear is engaged a ramp with a defined slope on the reverse gear selector plate actuates the switch. The electrical circuit to the reversing lights is made.Reversing light switch F4Gearbox housingRamp SSP247_067 Reverse gear selector plateElectrical circuit D +15 F4 M16 M17 Ignition starter switch, terminal 15 Reversing light switch Left reversing light bulb Right reversing light bulb+15 D S7 10AF4M16M17SSP247_06843All rights reserved, including the right to make technical changes. AUDI AG Dept. I/VK-5 D-85045 Ingolstadt Fax 0841/89-36367 040.2810.66.20 Technical status 03/00 Printed in Germany247