Due to a lot of questions regarding the verification of clutch components and diagnostic problems, Schaeffler conducts a number of theoretical and practical training and replacement of clutch components with our guidelines. We did such a clutch replacement in a Scania R 450 with a mileage of 595,000 km.
The reported issue was noise from the clutch housing area and a knocking sound when shifting gears. We replaced the clutch at Bosch Q-Serwisie Auto-Bodex from Miastko. Regardless of the verification result, it was decided to replace the complete clutch as a preventive measure at the mileage of about 600,000 km.
Photo No. 1
This vehicle is equipped with a robotic gearbox [ photo 1 ] whose control computer, after replacing the clutch, requires training for the parameters of the new clutch. However, with this Scania tractor unit, the learning curve takes place automatically during the first test drive.
When replacing clutch elements, the condition of the clutch shaft must be verified in order to prevent failure of the new clutch as a result of possible irregularities in the elements of the clutch system or the bearing of the clutch shaft.
The declutching system is responsible, among other things, for the so-called preload, i.e. permanent contact of the thrust bearing with the ends of the clutch pressure plate spring. The lack of proper preload results in the wear of the ends of the disc spring, the auxiliary ring that attaches the thrust bearing to it, which in this case is subject to premature wear.
Photo No. 2
During the disassembly of the gearbox, there was a problem with the inability to remove the thrust bearing from the pressure plate [ photo No. 2 ].
The reason for this was the high tension in the clutch release system caused by the clutch actuator. In this vehicle, the actuator is integrated with the clutch control unit, so we had to unscrew this unit from the gearbox housing [ photo 3 ].
Photo No. 3
After dismantling the gearbox, the clutch elements and parts cooperating with it were verified.
Photo No. 4
The condition of the friction surface of the flywheel had no signs of mechanical or thermal damage or wear [ photo 4 ].
Photo No. 5
The flywheel has only been cleaned and degreased. The linings [photo No. 5] on the clutch disc did not reach full wear and did not bear signs of thermal overload, the torsional vibration damper also did not have excessive play.
Photo No. 6 Such condition of the muffler proves the correct operation of the engine and the correct functioning of the clutch control system. The condition of the splines in the disc hub [ photo No. 5 ] and on the clutch shaft [ photo No. 6 ] had no signs of excessive wear.
Photo No. 7
In addition, no play was found on the bearing of the clutch shaft in the gearbox. On the other hand, a slight play (wear) on the internal splines of the clutch disc (connection of the hub with the torsional vibration damper) was verified [ photo 7 ], which confirmed the reported slight clatter during gear shifting.
Photo No. 8
Clutch pressure plate surface without signs of thermal overload and mechanical wear. In the pressure plate, wear of the ends of the disc spring was found [ photo 8 ], which indicated wear of one of the elements of the release system. This problem was indicated by the slightly increased noise of the thrust bearing.
Photo No. 9 After checking the elements of the release system, play was found on the axis of the forks transferring the force to the thrust bearing [ photo No. 9 ]. Due to the above, the pressure plate, clutch release bearing and fork were replaced. The reason for the constantly occurring noise was damage to the clutch shaft support bearing in the flywheel, which had a large play [ photo 10 ].
The clutch shaft support bearing was mounted in the flywheel socket with a sleeve resting on its outer race.
The disc is mounted with a centering pin to facilitate the insertion of the input shaft and prevent stresses in the bearing part of the friction linings and the hub. Until the first clutch actuation, sustained stresses can damage the disc. In addition, the positioning of the disc in the axis of the clutch makes it easier to embed the clutch shaft.
Photo No. 10
In the case of misalignment, the clutch shaft hits the faces of the hub wedges, causing their upsets and, consequently, the lack of smooth movement of the disc on the shaft when the clutch is engaged.
After the assembly of the parts in accordance with the LuK technology (information available on the REPXPERT.pl website) and the vehicle manufacturer's recommendations, a test drive was performed (automatic training in the control computer). No irregularities were found, so the car was approved for further use.
