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Damage Analysis Of Rear Cover Of Fast Transmission Caused By Improper Maintenance

September 4, 2008, Our company accepts the rear cover of fast gearbox (model: f99975) accident of early damage. After the gearbox is replaced with the rear cover, the outer ring of the gearbox combined bearing slips and the oil seal leaks oil. Because the customer does not provide all the damaged parts, we can only organize relevant technicians to analyze the cause of the accident according to the rear cover of the gearbox and relevant oral instructions provided by the customer:

Accident Phenomenon Of Fast Transmission:

The combined bearing hole of the rear cover is worn, and the positioning shoulder of the outer bearing outer ring of the combined bearing impacts with the rear cover shell to form grooves and wear areas.

Accident Phenomenon:

Accident Overview

Fast’s double intermediate shaft transmission is favored by vehicle manufacturers and users because of its high reliability, light weight, small size, strong bearing capacity and convenient maintenance. However, in the process of use, if we do not pay attention to the specification of normal use, the selection of spare parts is messy, and only repair instead of maintenance (replace where it is bad), the probability of damage to the transmission is also large.

The auxiliary box of fast double intermediate shaft transmission is also a double intermediate shaft structure. In the maintenance, it should be noted that only visible damaged parts cannot be replaced. The fault source should be found according to its working state and principle for comprehensive maintenance.

The main shaft of the auxiliary box also belongs to the floating shaft (although the 717 / 813 combined bearing can perform axial and radial positioning), but its front part completely depends on the extended intermediate shaft supported by 42037 bearing and 192310 bearing for floating positioning, that is, if these two sets of bearings are worn, the main shaft of the auxiliary box may have positioning deviation (radial runout exceeds the standard).

At the same time, because of the distribution of the gearbox in the vehicle, there is a certain inclination angle between the output shaft of the gearbox and the transmission shaft of the vehicle; The transmission shaft connected with the gearbox has a certain weight and is often doing violent variable load and high speed movement. This requires that the dynamic balance of the transmission shaft is very high, and the matching of the universal joint and flange fork of the transmission shaft is also very high.

It can be seen from accident analysis pictures 3 and 4 that during the rotation of the main shaft of the auxiliary box, the preload of the actual combined bearing has failed to meet the standard. While the main shaft of the auxiliary box rotates, there is also radial runout, which is reflected on the rear end face of the rear cover shell of the transmission. The positioning shoulder of the combined bearing has grooves and impact damage marks on the rear end face of the rear cover shell due to alternating stress; It also causes excessive wear on the contact surface between the reduction gear gasket and the rear cover housing.


Since the customer cannot provide the damage of other relevant parts, we can only make a rough analysis according to the existing damage:


1. When replacing the rear cover, the user did not check the damage of 42307 and 192310 bearings.

2. The user did not check the wear of 19466 (reduction gear gasket) during maintenance.

3. The user did not adjust the dynamic balance of the transmission shaft.

4. The fit clearance between the transmission shaft flange fork and the universal joint spider exceeds the standard.

5. The user replaced the combined bearing of the auxiliary factory.

6. The preload of 717 / 813 combined bearing does not meet the standard.

7. The user did not use the gearbox according to the normal operation after replacing the rear cover.

This accident is not a quality problem of the transmission rear cover.

For the corresponding test report, please contact the manufacturer or relevant technical appraisal organization directly.

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