Usage:
D250B, D300B, D25C, D30C, D35C, D350C Trucks
Reference: Service Magazine; February 16, 1987; Page 7; "New Linkage Ensures More Positive Release Of Park Brake."
The articulated dump trucks in the list that follows have a parking brake which is mounted on the output transfer drive. This parking brake is released by means of an air chamber.
- D250B: 5WD1-Up
- D300B: 4SD1-Up
- D25C: 9YC284-Up
- D30C: 7ZC1-Up
- D35C: 2GD76-Up
- D350C: 8XC131-Up
- D300B: 4SD1-Up
During normal operation the brake requires no attention other than a periodic check to ensure that it is not excessively worn. However, it is essential that the brake is correctly set up during initial assembly. If the parking brake is not set up correctly, the rubber diaphragm in the air chamber can be punctured.
There are two parking brake arrangements in service. The former arrangement is shown in Illustration 1. The reference article explains how to update the former parking brake arrangement to the current arrangement. The current arrangement is shown in Illustration 2.
Illustration 1. Former parking brake arrangement.
Parking Brake Adjustment Procedure
Use this procedure to adjust the current parking brake arrangement.
1. With the actuator linkage disconnected, check to ensure the brake plates turn freely. Check dimension (B). There must be 1.0 mm (.04") or more clearance between outermost friction disc (9) and end plate (10).
2. Turn nut (1) until dimension (A) is 12.0 mm (.47"). The nut must be installed with 9S3263 Thread Lock.
3. Screw pull rod (2) into sleeve (7).
4. Screw jam nut (3) and pivot (4) onto the pull rod. Make sure there is full pull rod engagement in the pivot. Tighten the jam nut against the pivot.
5. Apply air pressure to the chamber to fully extend the pull rod.
6. Install bushing (5) in the brake levers. Adjust the length of the pull rod by turning sleeve (7) [use a wrench on flats (8) below nut (1), while holding pivot (4) with a second wrench] until link pin (6) and hole in bushing (5) are in line. This will allow link pin (6) to be installed without force.
7. Complete the assembly.
8. Apply and release the parking brake twice while checking to be sure the linkage movement is free. Check to be sure the discs are free in the "OFF" position.
Illustration 2. Current parking brake arrangement.