The driving mode of the car is greatly influenced by the state of the clutch assembly, which serves to instantly disconnect the engine from the transmission mechanisms when changing gears, braking and stopping the car. In addition, the clutch serves to smoothly connect the engine with the transmission mechanisms when starting the car and after changing gears. In the event of sudden braking, the clutch protects the engine and transmission mechanisms from overload.
The average service life of a clutch in foreign cars corresponds to 1000–1200 thousand kilometers. Wear depends on the load and the driver's compliance with the correct driving mode. The clutch of modern domestic and foreign cars, in principle, does not require special maintenance, with the exception of adjusting the travel of the clutch pedal, and in some cars even the clutch clearance is adjusted automatically. As the pedal wears, it moves up toward the driver. In older vehicles, the fluid level in the clutch reservoir should be checked during maintenance.
When servicing a vehicle, it is necessary to check the functionality of the clutch every day before leaving and check the fluid level in the reservoir for hydraulic clutches. Every 15 thousand kilometers or as necessary, you need to check and adjust the clutch drive. After 30 thousand kilometers or after two years of operation, the brake fluid in the clutch hydraulic drive should be changed. After five years or after 150 thousand kilometers, it is necessary to replace the protective rubber covers and dampers that are used in the clutch cable drive, regardless of their technical condition.
Typical clutch malfunctions are:
clutch slipping (cause - lack of free play of the pedal or clutch release fork lever);
clutch slipping during normal free movement (reasons - oiling of the friction linings of the driven disk, flywheel and pressure plate surfaces, increased wear or burning of the friction linings of the driven disk, clogging or blocking of the sealing ring edge of the compression hole of the master cylinder, swelling of the cuffs of the master and working cylinders due to use of the wrong type of brake fluid or its contamination);
incomplete disengagement of the clutch, accompanied by noise in the gearbox (reasons: insufficient travel of the clutch pedal to engage the clutch with a backlash-free drive, increased pedal free play, air getting into the hydraulic line, air leakage from the hydraulic line system);
jerking when moving away (reasons: wear of the driven disk, jamming of the release clutch on the guide sleeve, breakage of damper springs, wear of the splines of the driven disk hub or input shaft, oiling of the friction linings of the driven disk, flywheel surfaces and pressure disk);
noise when the clutch is engaged (reasons: breakage or loss of elasticity of the damper springs, insufficient free play of the clutch pedal, breakage or loss of elasticity, or jumping off of the release spring of the clutch release fork);
sticking of the clutch pedal in the pressed position (reasons: breakage or disconnection of the release spring, clogging of the holes in the reservoir cover, jamming of the driven disk hub on the splines of the input shaft of the gearbox, breakage of the friction lining of the driven disk or loosening of the rivets, warping of the driven disk, malfunction of the clutch drive) .
The gearbox serves to change the traction force on the drive wheels of the car, and also ensures the vehicle's reverse and disconnects the engine and clutch from other transmission units when the box is switched to the neutral position. The transmission is characterized by two types: manual and automatic, and most modern cars are produced with an automatic transmission, the use of which provides reduced fuel consumption, higher quality gear shifting, and a large selection of driving modes, for example, winter, sport, economical.
When servicing an automatic transmission, the oil level must be checked at least every 15 thousand kilometers. The oil is changed every three years, but no later than after 45–50 thousand kilometers. If the car is used in rural areas or as a taxi, the oil is changed after 35 thousand km. For automatic transmissions, only special oil is used.
When servicing the drive axle and manual transmission, every day before leaving, you need to make sure that there are no oil leaks in spots in the parking area from the gearbox and drive axle, noise on the operating gearbox, and the ease of gear shifting. After 15–30 thousand kilometers, it is necessary to check the oil level in the cooled box and drive axle and, if necessary, top it up. Around the same time, it is necessary to clean the transmission breather on front-wheel drive cars or the rear axle housing on a car with a classic layout. After 70–100 thousand kilometers, the oil in the gearbox and drive axle should be replaced.
When checking, there should be no cracks on the crankcase, and no wear or damage on the surface of the bearing seats. There should also be no damage on the mating surfaces of the clutch housing and the cover that could cause divergence of the axles and insufficient tightness, which could lead to oil leakage. There should be no damage or unevenness on the working edges of the oil seals. Allowable wear of the working edge width is not more than 1 mm. Seals should be replaced even if there is minor damage or loss of elasticity, but it is best to use new ones when assembling the gearbox.
Damage and excessive wear are not allowed on the working surfaces of the driven shaft splines. There should be no visible irregularities on the bearing race surface at the front end of the driven shaft and in the drive shaft bore. The intermediate shaft teeth must not be discolored or excessively worn. The splines and grooves of the shafts must be free of dents, burrs and wear to ensure a backlash-free fit of the synchronizers. The surface of the reverse gear axis should be smooth, without any signs of binding. In case of major damage and deformation, the shaft is replaced with a new one.
When servicing the gear selection and shift mechanisms, check the condition of the gear selection lever, locking brackets, gear selection rod, oil seal and protective ring for securing the gear selection lever. Worn and damaged parts should be replaced. They also check the fit of the gear shift lever in the ball joint, which should turn freely in the support, without jamming, and not have free play. Deformation of the drive rod and damage to the protective cover are not allowed.
When inspecting the reverse locking mechanism, check the axis of the locking mechanism. It should be held tightly on the base, and the lever, after turning it to each of the two extreme positions, should return automatically under the action of a spring to its original middle position. The lever in its original position should not have free play when rocking it by hand.
When servicing the cardan drive, check daily for knocking, increased vibration and noise. The condition of the driveshaft without disassembling it is checked with the car raised or in an inspection ditch. Inspect the driveshaft for nicks, cracks, or bent shaft pipes. If they are found, the shaft should be replaced. To check the clearance in a cardan joint or spline joint, take the shaft near the joint with one hand, try to turn it to the sides or rock it with the other, and also lift each side of the joint. Increased play in the cardan drive and other transmission units can be determined using play meters.
By external inspection, check the condition of the universal joint seals and spline joints. Inspect the front elastic rubber coupling. There should be no damage or swelling of the rubber or splits around the mounting bolts. The presence of oil contamination indicates wear of the rear gearbox oil seal, and on the rear universal joint - wear of the final drive oil seal.
The intermediate support is inspected in the same way. The intermediate support bearing is checked by lifting the shaft. If movement (play) is felt, the bearing must be removed and its condition checked by turning the outer ring by hand. If significant wear occurs, the bearing should be replaced.
Every 10 thousand km, you should check and, if necessary, tighten the bolts and nuts securing the universal joint flanges and the intermediate supports of the propeller shaft. After 40–60 thousand kilometers, the splined joint of the propeller shaft is lubricated with grease. During the inspection, it is also necessary to check the tightness of all mounting blocks.
When servicing the front wheel drive, every 15 thousand km, and when driving on unpaved or gravel country roads, check and clean the protective covers of the joints much more often.
When the rear drive axle is operating, noise, knocking, increased heating, and oil leakage may occur. The main reasons for constant noise and heating during operation of the rear drive axle may be the following: insufficient oil level or the use of the wrong type; incorrect adjustment of the engagement of the bevel gears of the main gear; wear or destruction of drive gear bearings; loosening of the drive gear flange; breakage of gear teeth; wear of the spline connection of the semi-axial gears; deformation of the rear axle beam or axle shafts.
The main causes of noise when accelerating and braking a car by the engine can be: increased clearance in the drive gear bearings, their wear or destruction, incorrect lateral clearance between the teeth of the final drive gears.
The main causes of noise when turning and sudden changes in engine crankshaft speed are: jamming of the journals of the semi-axial gears, jamming of the satellites, loosening of the differential cup bolts, incorrect adjustment of the differential gears, tight rotation of the satellites on the axle.
Noise from the rear wheels can be caused by: loosening of the wheels, wear or destruction of the ball bearing of the axle shaft.
The causes of noise and knocking when the car starts to move can be an increased gap in the splined connection of the drive gear shaft with the flange, wear of the hole for the pinion axis in the differential box, or loosening of the rear suspension torque rod mounting bolts.
The causes of oil leakage are wear or damage to the oil seals, damage to the sealing gaskets, and loosening of the crankcase mounting bolts.
If the driveshaft rotates, but the car does not move, then either the axle shaft keys have broken off or the axle shaft is broken.
Determining the condition of the rear drive axle without disassembling itTo check the performance of the differential, you can hang up the rear wheels of the car by placing the gearbox lever in the neutral position. Rotate one of the rear wheels with your hand and watch the other wheel. If it rotates in the opposite direction without knocking or noise, then the differential is working. Rotation of both wheels in one direction indicates a faulty differential.
One of the common malfunctions of the drive axle is the appearance of noise during various modes of its operation. To determine the causes of noise, the following tests should be carried out.
In the first test, in order to accurately determine the nature of the noise, the car is driven at a speed of about 20 km/h and gradually increased to 90 km/h, listening to different types of noise and noting the speed at which the noise appears and disappears. Then you should release the throttle pedal and, without braking, reduce the engine speed. If noise occurs, then most likely it comes from the gears of the gearbox, since they are loaded. During deceleration, you should monitor the change in noise, as well as the moment when the noise intensifies. The noise usually occurs at the same speeds during both acceleration and deceleration.
In the second test, the car is accelerated to 100 km/h, the gearshift lever is placed in neutral and, with the ignition turned off, the car is allowed to roll freely until it stops. In this case, you should monitor the nature of the noise at different deceleration rates. When turning off the ignition, you should be careful and careful. Do not turn the key more than necessary to turn off the ignition, as further turning to the “Parking” position may trigger the anti-theft device.
The noise observed during this test, which corresponds to the noise during the first test, does not come from the final drive gears, since they cannot cause noise without a load. The noise noted in the second test may come from the differential gears or bearings or the differential.
To perform the third test, with the car stationary and braked, start the engine and, gradually increasing the speed of its crankshaft, compare the resulting noises with those noted in previous tests. Noises similar to those encountered during the first test indicate that they do not come from the gearbox, but are caused by other components. To confirm that the noise is coming from the gearbox, raise the rear wheels, start the engine and engage high gear. In this case, you can make sure that the noise really comes from the gearbox and not from other components, such as the suspension or body.
More accurate data can be obtained by testing the drive axle using appropriate equipment.
We will provide maintenance and transmission repairs at the highest level, after which the car’s performance on the road will be much better.
Failures in transmission elements most often occur gradually. The car can be used, but when changing gears or pressing the clutch, problems sometimes begin to occur. In such a situation, maintenance and repair of the car transmission will be the least expensive for the car owner, since there will be no need to change expensive elements.
In our workshop, the price for transmission service and repair is one of the most affordable in Moscow. Our clients receive services from true professionals with many years of experience. Our technicians carry out diagnostics and troubleshooting using the best modern equipment, which allows us to achieve high quality repair work. If you contact us, the transmission will work stably.
How to identify transmission malfunctions?
Transmission maintenance means quite complex repair operations that only professional craftsmen can handle. During prolonged use, such an important vehicle system is subjected to significant loads that cannot pass without leaving a trace. It is in such situations that diagnostics and transmission repair are required, which is carried out using specialized equipment.
Prompt technical repairs of the transmission should be carried out in the following cases:
- If difficulties arise during gear shifting.
- When vibrations, rattles and various extraneous noises appear while driving.
- If significant jerks occur at the beginning of the movement.
- In case of excessive oil leakage.
If at least one of the listed phenomena occurs, you should immediately contact a car service. After conducting a detailed diagnosis, experienced technicians will very quickly identify the cause of the breakdown and take all necessary actions to effectively eliminate it. High-quality transmission repairs, the prices of which are very affordable, will ensure a safe and very comfortable ride.
Daily maintenance.
Check the oil level in the hydromechanical gearbox. When starting off and while driving, check the operation of the clutch, gearbox, cardan and main gears. Make sure there are no oil leaks from the crankcases of the units.
First maintenance.
Check the fastening of the clutch housing to the cylinder block, the condition of the clutch release and auxiliary springs, the fluid level in the master cylinder, the free and full travel of the clutch pedal, the fastenings of the mechanical or hydromechanical box. After one TO-1, check the correctness of the automatic gear shift modes, the operation of the starter lock, the automatic neutral switch and tighten all the terminal connections of the electric drive of the LiAZ-677 hydromechanical gearbox. Check and tighten the loose bolts securing the support plates of the needle bearings, propeller shaft flanges and intermediate supports: check the condition of the cardan shafts.
Check the fastening of the gearbox cover and housing and the absence of leakage at the connectors and connections; lubricate the gear shift control roller and the clutch pedal roller with grease (on the LAZ-695 bus).
Lubricate the intermediate supports of the cardan shafts with grease; needle bearings of cardan joints - with TAp-15 or TAp-10 oil; bearings of the front support of the hydromechanical transmission - lubricated.
Check the oil level in the rear axle housing and wheel drive and, if necessary, add oil DP-14, DP-11 or all-season TAp-15, and pour TS-14.5 oil with Chloref-40 additive into the PAZ-672 rear axle housing.
Second maintenance.
Check the condition and fastening of the clutch release lever spring, the fastening of the clutch hydraulic cylinders, the condition of the clutch release bearing and the gap between the bearing and the clutch release levers.
Check the condition and fastening of the gearbox covers, the gearshift lever bracket and the operation of the remote gearshift drive (on the LAZ-695N bus).
Check the adjustment of the peripheral spool control mechanism and the fastening of the bearing caps. Once a year, check the serviceability of the oil temperature warning lamp sensor in the automatic transmission system and the operation of the electromagnets. After 15 thousand kilometers, change the oil in the automatic transmission. After one TO-2, check the tightness of the flange nut of the main gear drive bevel gear. Once a year, check the tightness of the final drive ring gear support nuts, the tightness of the differential cup mounting bolts, and the engagement of the final drive gears.
Adjusting the clutch pedal free play of the LAZ-695N and Ikarus-260 buses. The free play of the clutch pedal of LAZ-695N and LAZ-695M buses consists of two gaps. The first gap between the pusher and the master cylinder piston is equal to 0.5 mm, which corresponds to a pedal free travel of 6-12 mm, and the second gap between the clutch bearing and the release levers, which should be 3-4 mm, which corresponds to a pedal free travel of 35- 40 mm.
To adjust the first gap, it is necessary to remove the release spring, disconnect the shield from the pedal lever, unscrew the lock nut, holding the rod from turning with a wrench, and, turning the rod fork, set the pedal free play to 10 mm until the rod stops in the piston of the main cylinder, tighten with the lock nut and assemble the entire assembly .
When operating a bus, the first gap practically does not change; it is adjusted only when parts are replaced. The gap between the clutch bearing and the clutch release levers decreases due to wear of the friction linings, which leads to clutch slipping. To adjust the second gap, you must: remove the clutch housing cover; disconnect the rod and tension spring from the lever; Unscrew the lock nut, holding the rod nut o with a wrench from turning (which, when adjusting, must be pushed into the cylinder until it stops); By changing the length of the rod, adjust the gap between the clutch bearing. Turn off and release levers, which should be equal to 3-4 mm. After this, assemble the entire assembly. The free play of the clutch pedal of the Ikarue-260 bus is adjusted in the same way. The gap between the working cylinder pusher when the tension spring is removed should be 4-5 mm, and the free play of the pedal should be 20-25 mm. On the PAZ-672 bus, the free play should be 25-30 mm.
On the Ikarus-260 bus, in addition to adjusting the free play of the clutch pedal, the position of the pedal is adjusted using the servo spring pre-compression adjusting bolt. The pedal position is adjusted so that the distance between the extension of the bolt axis and the center of the axis of the master cylinder rod pin is 5-1 mm. The pre-tension of the servo spring is adjusted with a bolt so that when the support pin of the pedal lever passes through the dead center, the coils of the servo spring do not close.
Removing air from the hydraulic clutch of buses LAZ-695, PAZ-672 and Ikarus -260. The presence of air in the clutch hydraulic drive leads to incomplete disengagement of the clutch. To remove air from the clutch hydraulic drive, it is necessary to: fill the master cylinder reservoir with brake fluid to a level 10-15 mm below the upper edge of the reservoir; remove the protective cap from the head of the bypass valve of the working cylinder and put a rubber hose on the head; immerse the free end of the hose in brake fluid poured into a glass half-liter jar, half filled; create pressure in the system by sharply pressing the clutch pedal 4-5 times with an interval of 1-2 s; Keeping the pedal pressed, unscrew the bypass valve of the working cylinder ½-¾ turn. Liquid with air bubbles will escape into the vessel; when air bubbles stop escaping (clean transparent liquid will flow out), close the bypass valve until the liquid level is up to normal, remove the hose and put on the cap.
In the same way, air is removed from the hydraulic clutch of the Ikarus-260 bus. The difference is that the brake fluid is poured into a special reservoir connected by a pipeline to the master cylinder. To remove air, bypass valves are installed in the main and working cylinders.
Adjusting the remote gear shift drive. On the LAZ-695M and 695N buses, the remote drive of the box is adjusted using traction. To adjust, you need to put the lever in a vertical position and, by changing the length of the rod using the adjusting fork, achieve a neutral position of the gears in the gearbox
Preparing for work and checking the serviceability of the hydromechanical gearbox. Check the presence of oil with an oil measuring rod, start the engine, with a small opening of the throttle, brake the bus and turn the controller lever to position A, warm up the oil in the pan to 40°C, put the lever in position H and check the oil level again, move the controller lever to position A and check the operation of the hydromechanical transmission at low engine speed in idle mode. At 450 rpm of the engine shaft, the bus should not move. When the engine speed increases, starting should be smooth. When accelerating the bus and at medium throttle opening, switching to direct transmission should occur at a speed of 18-20 km/h (felt by a slight jolt), and blocking of the transformer should occur at a speed of 28-30 km/h. Unlocking the torque converter should occur at a speed of 23-25 km/h, and switching to a downshift at a speed of 14-16 km/h. When accelerating the bus at full throttle opening, direct transmission should be engaged at a speed of 28-30 km/h, and the torque converter should be locked at a speed of 38-42 km/h, the torque converter should be unlocked when the speed decreases to 35-37 km/h, and the transition in first gear - at a speed of 23-25 km/h. To fill hydromechanical transmissions, grade A oil for automatic transmissions is used. The first oil change is carried out after 1000 km, and the subsequent ones - after 15 thousand km. To drain the oil, you must: clean the pan of the box and torque converter from dirt; install a special tray under the box; unscrew the magnetic plug and drain the oil from the pan; through the hole in the lower part of the crankcase, remove the two pump wheel plugs one by one and drain the oil from the torque converter. When refueling, you must: pour about 10 liters of oil through the hole in the oil measuring rod, start the engine and maintain idle speed for 2-3 minutes. After this, when operating at engine crankshaft speed in idle mode, add up to 5 liters of oil and, after waiting 1 minute, turn off the engine and check the oil level. Top up if necessary. The full filling capacity is 16 liters.
To check and adjust the peripheral valve control mechanism, remove the cover of the peripheral spool switch and move the guide with your finger to the first gear position, towards the engine. Turn on the electromagnet Ml and check the gap between the end of the adjusting screw and the pusher of the electromagnet Ml. The gap should be 0.2 mm. If necessary, make adjustments with the screw. After this, turn off the magnet of the first gear, move the leash to engage the second gear and carry out the same check and adjustment as for the first gear. When adjusting, the peripheral valve should be located opposite the driver. After adjustments, lock the adjustment bolts and close the cover. The contacts of the automatic neutral switch should close when you press the throttle control pedal and move it within 10-15 mm. If adjustment is necessary, loosen the screws securing the switch, adjust it by turning it on at the specified moment and fasten it again.
Adjustment of automatic switching moments. transmissions are carried out by a screw on the main spool lever. When the screw is screwed in, the spool moves out of the sleeve. In this case, gear shifting occurs at a higher speed of the bus. When the screw is unscrewed, the spool moves in and the transition to the next gears occurs at lower speeds. Significant unscrewing of the screw is unacceptable, as this may lead to direct transmission being engaged while parked or when starting off.
Checking the level and changing the oil in the main gear. To check the oil level in the crankcases of the main gear and wheel drives, it is necessary to unscrew the control plug of the main gear filler hole and the control plugs of the wheel drives. The oil level should be at the lower edge of each inspection plug hole. To change the oil, it is necessary to unscrew all control plugs when returning the car (bus) from the line. Having prepared the container for the oil, unscrew the drain plug of the main gear and the plugs in each wheel gear. After draining the oil, tighten the drain plugs and pour oil through the control plugs of the wheel drives to the level of the lower edge of each filler hole, then tighten the plugs.
Checking the serviceability of the cardan transmission. Checking the fastening of the flanges is carried out on the bus with the parking brake mechanism released and the gearbox lever in neutral position. If, when rocking the yoke flanges of the cardan transmission, loosening of the flanges is detected, it is necessary to disconnect the corresponding end of the propeller shaft, unscrew the flange mounting nut, and then tighten it until it stops and tighten it. All propeller shaft flange mounting bolts must be carefully tightened. By rocking the cardan shaft around the axis, make sure there is no play in the cardan bearing.
When assembling the propeller shaft or when replacing it on a new car, it is necessary to align the arrows stamped on the shaft pipe and on the sliding fork to prevent imbalance.
Lesson #48
The main transmission units are the clutch, gearbox, rear axle (final drive and differential), and cardan drive. Transmission units account for about 10% of the total technical impact on the car.
When diagnosing transmission mechanisms, first of all, the driver’s information about the operation of its units, vehicle overrun, spontaneous gear shifting or difficulties in turning them on, noise and overheating observed during vehicle operation on the line are taken into account. The results of an external inspection (no leaks, deformations, etc.) and data on mechanical losses in the transmission, determined on a stand with running drums, are also taken into account.
Clutch. Signs of clutch malfunctions are: slipping under load (due to lack of free play, weakening of pressure springs, oiling of the friction linings or their wear); incomplete shutdown (due to increased free play, skewed levers, jamming or warping of the disk); sudden activation (as a result of jamming of the release clutch, breakage of damper springs, wear of the splines of the driven shaft hubs); heating, knocking and noise (due to bearing destruction, loosening of the rivets of the disk lining, violation of the position of the switch levers).
Clutch slipping is checked on a stand with running drums using a stroboscopic gun. A load is created on the driving wheels of the car using the load device of the stand and in the mode of maximum traction force (at a speed of 50 km/h), in direct gear the driveshaft is illuminated with a stroboscopic lamp. If the clutch slips, the driveshaft will appear motionless because it works as one unit with the engine crankshaft. Detected malfunctions of the clutch mechanism are eliminated by adjusting the free play of the clutch pedal or by repairing in the TP zone.
The activation mechanism is diagnosed by the free movement of the pedal, the completeness of the clutch engagement, a certain ease of gear engagement, the absence of slipping when transmitting torque and the smoothness of the engagement.
Rice. 1. Angle playmeter
Gearbox and rear axle.
Signs of a gearbox malfunction are: self-switching off (due to incomplete engagement of gears, misalignment of the drive, wear of bearings, teeth, splines, shafts, clamps); noise when switching (due to incomplete engagement of the clutch or synchronizer malfunction); increased noise, vibration, increased mechanical losses when testing on a stand with running drums.
Signs of rear axle malfunctions may include increased vibrations, noise, heating, play and increased mechanical losses due to wear or breakage of gear teeth, wear of bearings and their seats, loose fastenings, and misalignment of gear pairs.
The vehicle's gearbox and rear axle are diagnosed based on backlash, vibration and thermal condition. For backlash diagnostics, an angular backlash meter is used (Fig. 30.19), which allows you to measure transmission backlash under the influence of a given torque. To perform this operation, tighten the handbrake all the way. The jaw of the dynamometer is placed on the crosspiece of the propeller shaft at the rear axle. Then, turning the drive shaft in one direction with the play meter handle, select the gap and set the scale of the graduated disk so that the liquid level in the semi-ring on the disk coincides with the zero mark of the scale. By turning the playmeter in the other direction, select the gap and determine it by changing the position of the liquid level. The moment of force when choosing the driveline clearance should be within 20-25 Nm.
The next step is to determine the angular clearance in the rear axle. To do this, brake the rear wheels (with a foot brake) and, with the gearbox in neutral, use a backlash meter to determine the total backlash of the rear axle.
The total angular play of the cardan drive should be no more than 4°, the gearbox in first gear - 2.5, second -3.5, third -4, fourth -6 and reverse gear -2.5; rear axle two-stage -45 and single-stage -35°.
Cardan transmission. Signs of driveline drive malfunctions may include noise, vibration and sharp knocking noises in the driveshafts that occur when the car is moving at the moment of changing from one gear to another and with a sharp increase in engine speed (for example, when moving from engine braking to acceleration).
These malfunctions arise due to significant wear of the cardan forks, needle bearings, crosspieces and splined joints of the cardan joint, as a result of which the balancing of the cardan shaft is disrupted and significant shock loads occur on the needle bearings.
Diagnosis of the cardan transmission is performed using a backlash dynamometer. Based on the play of each driveshaft joint, the degree of wear of each driveshaft and spline joints is determined. The total play of the cardan shaft should be no more than 4°, each width should be no more than 1.5°. To determine the runout of the driveshaft, it is necessary to install the car in an inspection ditch, hang its drive wheels and install a clamp with an indicator head on the frame side member (when diagnosing on a stand with running drums, the wheels do not need to be hung) so that the indicator measuring rod comes into contact with the tension 1-2 mm with the middle of the intermediate (main) propeller shaft pipe. Engage the first gear in the gearbox and turn the crankshaft (propeller shaft) one revolution using the starting handle. The driveshaft runout should be no more than 0.6 mm for passenger cars and no more than 1.2 mm for trucks.
Hydromechanical transmission (HMT). Signs of malfunctions of a hydromechanical gearbox are: failure to engage a particular gear when the vehicle is moving due to failure of the electromagnets, jamming of the main spool, failure of the hydraulic valves, destruction of o-rings and seals, misalignment of the automatic gear shift control system; jerks when changing gears due to misadjustment of the peripheral valve spool switch or loosening of the centrifugal regulator and main spool brake; discrepancy between gear shift moments (travel speeds at which gear shifts should occur) and the degree of opening of the engine throttle valve due to a violation of the automatic gear shift moments adjustment or malfunctions in the operation of the power and centrifugal regulators (bent, jammed rods and levers, loose fasteners); low oil pressure in the main line due to wear of oil pump parts or excessive internal oil leaks in the transmission; increased oil temperature at the drain from the torque converter or in the hydraulic transmission sump due to warping or increased wear of the clutch discs.
GMP is diagnosed at post D-2 on the traction qualities test stand (STK). The stand reproduces the necessary control modes for diagnosing GMF - acceleration, coasting, braking, steady motion in each gear. At the same time, in each of the vehicle’s driving modes, a special device is used to measure the current value of the driving speed and record the speed values at the moments of automatic gear shifting.
The moments of automatic activation of a particular gear are recorded using electrical impulses coming from the actuators of the automatic gear shift control system.
Oil pressure in the main line is measured at idle, driving and coasting modes using a sensor installed in the driver's cabin. To measure the oil temperature in the hydraulic transmission unit, a high-speed, low-inertia heat measuring device is used. In addition, using a special feeler gauge, the gaps between the ends of the electromagnet pushers and the adjusting screws of the peripheral valve spool control mechanism are measured. Based on the diagnostic results, the need for adjustments in the automatic gear shift control system is identified and the need to remove the GMT from the vehicle for repair is determined.
It should be noted that the GMF can be used to determine the technical condition of the car engine on which it is installed as a kind of “load”, which makes it possible to check its power indicators in a certain mode.
Maintenance of transmission units. During TO-1, the fastening of the clutch, gearbox, cardan drive, rear axle is checked and, if necessary, the fasteners are tightened.
The free play of the clutch pedal corresponds to the established gap between the release bearing and the clutch release levers (1.5 = 3 mm) and for most domestic trucks it is 30-SO mm, and for cars - 20-40 mm. For cars of the MAZ family, the clutch pedal has free play They check in the same way, but with the air deflated from the pneumatic system.
For cars with a mechanical clutch drive of the ZIL, GAZ, MAZ, LAZ families, free play is adjusted by changing the length of the clutch engagement rod. In the clutch of cars with a hydraulic drive "Volga", "Moskvich", VAZ, the free play of the clutch pedal is adjusted by changing the length of the rod of the working (executive) cylinder.
In a KamAZ vehicle, the clutch release drive is adjusted in two ways: by adjusting the gap between the pusher and the master cylinder piston and by adjusting the free play of the clutch release fork lever. The gap between the master cylinder piston and the piston pusher is adjusted with an eccentric pin on which the upper end of the pusher is fixed. This gap should ensure that the pedal moves within 6 = 12 mm. The free play of the release fork lever is adjusted using the spherical nut of the pneumatic hydraulic piston pusher, by turning which, the free play of the fork lever should be set within 3.7-4.7 mm. As a result, the free play of the clutch pedal should be 30-42 mm.
Lubrication work consists of the following operations: The pedal axle bushings and the clutch release fork of the ZIL-130 car are lubricated through grease nipples with US-1 grease until fresh grease appears, the release bearing is lubricated by turning the grease cap 2=3 turns or through two grease nipples grease-supercharger (cars of the MAZ, KamAZ family), For ZIL-130 cars, the release bearing is not lubricated during operation, since it is filled with lubricant during assembly at the factory,
Monitor and, if necessary, replenish the oil level in the gearbox, rear axle, transfer case, wheel drive of the rear axle (cars of the MAZ family and buses of the LAZ and LiAZ families).
Lubricate the cardan bearings and the intermediate support bearing with Litol-24 or 158 grease until lubricant appears through a special valve on the cardan cross. Check the condition of the seals on the cardan crosses and the rubber covers on the spline joints.
During TO-2, the drive of the gearbox and divider is monitored and, if necessary, adjusted. Clean the breathers of the gearbox and rear axle. Check and, if necessary, adjust the bearings of the drive gear shaft of the vehicle's gearbox by changing the number of adjusting washers that ensure preload of the bearings, and replace the oil.
In case of CO, the oil in the crankcases of transmission units is replaced in accordance with the time of year. When changing the oil, wash the transmission crankcases with diesel fuel and clean the magnetic plugs.
Maintenance of hydromechanical gearbox.
During EO, check and, if necessary, add oil to the GMF,
During TO-1, the fastening of the hydraulic transmission unit to the base of the body, the fastening of the oil pan and the condition of the oil pipelines are checked. Check the fastening of the electrical wires, the correct adjustment of the peripheral spool control mechanism,
During TO-2, they check the fastening of the bearing caps and the torque converter housing to the gearbox housing, the correct adjustment of the automatic gear shift modes, the oil pressure in the system, the serviceability of the oil temperature sensor, the condition and fastening of the speedometer sensor,
Current repairs (TR)
TP is carried out as required and includes the elimination of failures and malfunctions by performing repair operations with partial or complete disassembly of vehicle components and assemblies or replacing them with serviceable ones.
The cardan and final drives are quite durable and after adjustments at the factory during operation do not require additional adjustments, only in rare cases is this necessary.
TR of the cardan transmission begins with thorough cleaning and washing it of dirt. Then it is necessary to mark all mating parts with a core or paint in order to maintain balance. For disassembly and reassembly, special tools and devices must be used (punches made of soft materials, pullers of retaining rings, bearings, presses, etc.). When assembling, pay special attention to the integrity of the seals, the alignment of the marks, the presence of plugs in the sliding forks and the lubrication of parts. For spline joints, use grease Fiol-1, bearings – L3-31, Fiol-2U, grease No. 158. To take into account thermal expansion, the crosspieces must have axial play according to the manufacturer’s recommendations (approximately from 0.04 to 0.2 mm). This is achieved by installing gaskets or the thickness of the retaining rings of the spider bearings. TR of the final drive of passenger cars can be performed in a vice, and of trucks - on special stands. If damage is detected on one of the parts, they are replaced by a mating pair (for example, a drive gear with a driven gear). After replacing the parts, begin assembly and adjustment, connecting the parts according to the marks and lubricating them with transmission oil according to the lubrication chart for this model
Clutch maintenance. At EO check: the clutch action when starting the car and changing gears in driving mode; fluid level in the clutch hydraulic reservoir.
At TO-1 check: the operation of the drive and the free play of the clutch pedal (if necessary, eliminate malfunctions in the clutch drive and adjust the free play of the clutch pedal); tightness of the hydraulic drive of the clutch release mechanism (if necessary, eliminate leaks); fastening the clutch pneumatic booster.
At TO-2 check and, if necessary, tighten the fastenings of the clutch housing and hydraulic clutch cylinders.
Clutch diagnostics. The serviceability of the clutch is checked with the engine running. Depress the clutch pedal and shift gears one by one. If shifting gears is difficult and is accompanied by a grinding noise, then the clutch does not disengage completely (“drives”). The complete engagement of the clutch is checked by applying the handbrake. Then engage the highest gear and smoothly release the clutch pedal while simultaneously pressing the throttle pedal. If the engine stops, then the clutch is working properly. Continued engine operation indicates incomplete engagement (slippage) of the clutch. Slipping also occurs when the car is moving (slow acceleration and insufficient traction of the car with the rated engine power). When checking the clutch, the following malfunctions may be detected: sudden engagement, excessive heating of parts, noise, vibration and jerking when engaged. Clutch diagnostics can be carried out on a stand to check traction and economic indicators using a stroboscopic device.
Clutch adjustments and repairs. Clutch adjustments. During operation, the clutch is adjusted, but before that, the free play of the clutch pedal is checked. To do this, use a ruler with divisions and two sliders. One end of the ruler is installed on the floor of the cabin, and the upper slider is combined with the clutch pedal platform. Then press the pedal until the resistance sharply increases as it moves. This position is marked on the ruler with the second slider, and it corresponds to freewheel selection. The distance between the engines on the ruler will be the value of the free play of the clutch pedal.
At mechanical clutch drive The free play of the pedal is adjusted by changing the length of the main rod, unscrewing or screwing the adjusting nut along the rod (when the nut is unscrewed, the free play of the pedal increases, and when screwed in, it decreases).
At hydraulic drive The free play of the clutch pedal consists of free moves and gaps in the mechanical and hydraulic parts of the drive. Before adjustment, measure the full stroke of the working cylinder pusher. If the pusher stroke is less than the required value, this indicates a violation of the pedal free play adjustment or air entering the hydraulic drive system. In this case, it is necessary to bleed the hydraulic drive and then adjust the free play of the clutch pedal. The clutch hydraulic drive is pumped in the following sequence: remove the cap from the head of the bypass valve on the working cylinder, put a rubber hose on the valve, the end of which is lowered into a transparent container with a small amount of brake fluid. The air pump hose is screwed onto the threaded tip of the master cylinder plug and, by unscrewing the bypass valve half a turn, the pump creates pressure inside the master cylinder. Pressure in the system can be created by pressing the clutch pedal. In this case, when you press the pedal, the valve is unscrewed, and when released, it is turned in (this is necessary to avoid air entering the system through the valve). Under the influence of pressure, the liquid begins to flow into the container and air comes out in the form of bubbles along with it. As soon as the release of air bubbles stops, pumping is completed, the bypass valve is screwed on and the cap is put on it.
Next, check and, if necessary, set the required gap between the pusher and the master cylinder piston. Preliminary rough adjustment of the gap is made by changing the length of the rod, final adjustment is made by turning the eccentric bolt. This adjustment is assessed based on the pedal travel, which should be 3.5...10 mm until the pusher stops in the piston. The gap between the release bearing and the release levers is set by changing the length of the working cylinder pusher. With the fork tension spring removed, the stroke of its outer end should be within 4...5 mm, if the adjustment is carried out correctly.
Clutch malfunctions, their causes and solutions. During intensive use of the vehicle, various clutch malfunction. There are malfunctions of the clutch itself and malfunctions of the clutch drive. Clutch malfunctions include: wear and damage to the driven disc linings; deformation of the driven disk; oiling of the driven disk linings; wear of the splines of the driven disk; wear or breakage of damper springs; broken or weakened diaphragm spring; wear or breakage of the clutch release bearing; flywheel surface wear; wear of the pressure plate surface; jamming of the clutch release fork.
The main malfunctions of the mechanical clutch drive include: jamming, elongation or damage to the cable; damage to the lever system. The main malfunctions of the hydraulic clutch drive include: clogging of the hydraulic drive; violation of system tightness ( leakage of working fluid, presence of air in the system); working cylinder malfunction ( cuff damage).
Wear and failure of clutch structural elements occur mainly due to violations of vehicle operating rules: Pulling away at high speeds, foot on the clutch pedal while driving. One of the reasons for breakage or wear may be maximum service life of clutch elements. This applies to a greater extent to the clutch driven disc, which has a limited resource. If the operating rules are followed, this element will serve regularly for over 100 thousand kilometers.
The cause of clutch failure may be low quality components. When purchasing spare parts, preference should be given to original parts. Oiling of the friction linings of the driven disk occurs when oil gets on them due to wear or damage to engine or gearbox seals.
Clutch malfunctions are easily diagnosed by external signs. However, one external sign may correspond to several clutch malfunctions. Therefore, specific clutch malfunctions are usually identified during its disassembly.
Characteristic signs of a clutch malfunction: incomplete engagement (slipping), incomplete disengagement (the clutch “leads”), sudden engagement, jerking when the clutch operates; vibration when engaging the clutch; noise when disengaging the clutch.
Incomplete inclusionclutch characterized by the smell of burning friction linings of the driven disc, insufficient vehicle dynamics, engine overheating, and increased fuel consumption. Clutch slipping can be caused by lack of free play of the clutch pedal, wear, warping or oiling of the friction linings of the driven discs, breakage or weakening of the pressure springs and clutch release spring.
Incomplete shutdown accompanied by difficulty shifting gears while the engine is running, noise, crackling noise when changing gears, and increased free play of the clutch pedal. Incomplete disengagement of the clutch is possible when the free play of the clutch pedal increases, the discs are warped or skewed, the driven discs are stuck, the friction linings are broken, or the release levers are broken. In addition, on vehicles with a hydraulic clutch, incomplete disengagement of the clutch may be caused by air entering the hydraulic system, leakage of working fluid, or destruction of the rubber sealing ring of the master cylinder piston pusher.
Abrupt switching on clutch failure occurs when the clutch release clutch sticks on the drive shaft of the gearbox, loss of elasticity or breakage of pressure springs, wear or scuffing of the working surfaces of the pressure plate or flywheel, wear of the friction linings of the driven disk or weakening of the rivets.
Heating of parts, noise, vibration and jerking occur due to wear, destruction or insufficient lubrication of the release bearing, loosening of the rivets of the driven disk linings, increased clearance in the interface between the driven disk hub and the splines of the drive shaft of the gearbox. The appearance of a high-pitched hissing sound indicates a bearing malfunction.
Table 20 presents the main symptoms and corresponding clutch malfunctions.
Table 20
Main symptoms and corresponding clutch malfunctions.
