Usage:
NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
NOTE: This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS4827" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
NOTE: Some of the Affected Product fall into more than one group. Do all applicable portions of this Service Letter at the same time.
Termination Date
June 30, 1993Problem
The parking brake on certain D25D, D30D, and D350D Articulated Trucks may not have as long a service life as desired due to operators "driving thru the brake." A category three EMS warning can be installed which will sound an action alarm when the parking brake is engaged and the operator selects a gear.
Also, a new pressure switch has been introduced which will give earlier indication of low air pressure. Operation with low air pressure may result in parking brake drag. The improved pressure switch was introduced ahead of the moving off alarm, on the D25D and D350D Articulated Trucks. Therefore, some of the Affected Product which qualify for the moving off alarm will not need the air pressure switch modification.
Affected Product
Model & Identification Number
Group 1 - Low Air Pressure Switch
D25D (1HK1-262)
D30D (3AJ1-304; 1PK1-34)
D350D (9RF1-385)
Group 2 Moving Off Alarm
D25D (1HK1-310)
D30D (3AJ1-304; 1PK1-34)
D350D (9RF1-455)
Parts Needed
Group 1 - Low Air Pressure Switch
- 1 - 8T9792 Switch Assembly
Group 2 - Moving Off Alarm
- 2 - 2L8076 Terminal
- 1 - 5P5623 Wire (6 dm long) (2 feet of #16 wire - any color)
- 1 - 5P6001 Tube (1.5 dm long) (6 inches of .375" shrink tubing)
- 2 - 8S4626 Splice
- 1 - 2U6480 Shaft
- 1 - 2U6483 Bracket
- 1 - 2U6484 Bracket
- 2 - 9X0023 Switch
- 1 - 5P5623 Wire (6 dm long) (2 feet of #16 wire - any color)
Action Required
See the attached procedure.
NOTE: A 9S9150 Electrical Terminal Crimping Tool, a soldering iron, and solder will be required to complete this program.
Service Claim Allowances
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Attach. (1-Rework Procedure)
Rework Procedure
Group 1 - Low Air Pressure Switch
1. Remove the existing 6T1546 Switch Assembly and 6V9601 Adapter.
2. Install a new 8T9792 Switch Assembly in place of the 6T1546 Switch Assembly and 6V9601 Adapter that was removed.
Illustration - Installation of switch.
Group 2 - Moving Off Alarm
1. Park the truck on level ground and block the trailer wheels. Tilt the cab.
NOTE: Refer to Illustration 2 for Steps 2 through 6.
2. Disconnect the wires from reverse switch (1) and remove bracket (2) complete with the switch.
3. Remove cotter pin (4) and pin (5) to release clevis (3).
4. Remove the transmission control console cover and remove bolt (10) and washer (11).
5. Remove nuts (6.), bolts (7), and washers (8). Remove strip (9) complete with plate (12).
6. Remove (drive out) the existing shaft (13). This shaft will not be reused.
NOTE: Refer to Illustration 3 for Steps 7 through 20.
7. Put brackets (15) and (16) in position and install the bolts and washers that were used to hold the former bracket. (Bolts A and B) Do not tighten the bolts at this time.
8. Install new shaft (14), plate (12), strip (9), and the associated hardware. Make sure that plate (12) is correctly located on pin (19).
9. Install switches (17) and (18). Connect the wires that were disconnected in Step (2) to reverse switch (18).
10. Locate spare wires 409-Orange and 201-Black that are soldered and taped together within the insulating tubing used on the existing reverse switch wires. Cut away the solder joint and lengthen the two wires using 16 gauge wire. The preferred method to lengthen the wires is to strip the ends, solder, and protect the joint with shrink tubing. Alternately, a butt splice joint protected with shrink tubing can be used. Cut the added wire to enable connection of the wires to the Moving-Off Alarm switch. Install the ring terminals to the ends of the wires using the 9S9150 Crimping Tool. Connect these wires to the Moving-Off Alarm switch terminals.
11. Connect clevis (3) to shaft (14) using pin (5) and cotter pin (4).
12. Move the gear selector to first speed forward and check that switch (18) is properly engaged. Adjust the position of bracket (15) if necessary. When the bracket is properly adjusted, tighten bolt (A) that was installed in Step (7).
13. Move the gear selector to first speed forward and check that switch (17) is properly engaged. Adjust the position of bracket (16) if necessary. When the bracket is properly adjusted, tighten bolt (B) that was installed in Step (7).
Functional/Operational Check
14. With the parking brake engaged and the transmission in neutral, start the engine.
15. With the engine operating at low idle, move the gear selector to first speed forward. The EMS must give a stage 3 warning. (The parking brake indicator must be illuminated, the fault light must be illuminated, and the fault alarm must sound.)
16. Release the parking brake. The EMS warning must stop.
17. Engage the parking brake. The EMS warning must start again. Move the gear selector to neutral. The EMS stage 3 warning must stop.
18. Repeat the test for first speed reverse.
19. Move the gear selector to neutral, engage the parking brake, and stop the engine. Turn the electrical circuits on.
20. Move the gear selector to first speed reverse. The back-up alarm must sound and the reverse light must illuminate.
21. Move the gear selector to neutral. The back-up alarm must stop and the reverse light must go out. If necessary, make further adjustments to the positions of brackets (15) and (16). Adjust bracket (15) first and tighten bolt (A), then adjust bracket (16) and tighten bolt (B).
22. Ensure that the parking brake is engaged, the transmission is in neutral, and the engine is stopped before removing the wheel blocks.
Illustration 2 - Existing Parts
Illustration 3 - New Parts