Product Support Program For Adjustments Affecting Dual Stage Relief Valve In Transmission Control Group On Certain 785 Trucks, 789 Trucks, and Spare Transmissions Caterpillar

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 "PS4707" 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.

Termination Date

Problem

Some dual-stage relief valves on certain 785 Trucks, 789 Trucks, and spare transmissions may cause erratic operation of the transmission hydraulic control due to incorrect adjustments.

Affected Product
MOdel & Identification Number

785 (8GB1-614,8GB616)

789 (9ZC1-593)

Transmission Arrangements

3T0030 (3YB1-637)

3T0034 (2BE1-1306,2BE1309,2BE1310)

Parts Needed

1 - 8E8908 Spring

1 - 5J2721 Shim (use as required)

2 - 6J3993 Shim (use as required)

2 - 4M1751 Spacer (use as required)

1 - 6T2293 Piston

Action Required

See attached rework procedure.

Service Claim Allowances

NOTE: This is a 2-hour job.

When filing a claim for a spare transmission use the following serial numbers as the vehicle serial number:

NACD Dealers - 99Z21

CACO Dealers - 99Z621

CofA Dealers - 99Z121

CBSA Dealers - 99Z221

CFEL Dealers - 99Z821

COSA Dealers - 99Z421

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Attach.

(1-Rework Procedure)

Rework Procedure

1. Remove the large transmission cover from the top of the transmission.

2. Remove and disassemble the transmission control "D" station. Refer to illustration.

3. Remove the original 3T1437 Load Piston, the original (outer) 9W7410 Spring (light blue), and the original (inner) 7G5453 Spring (yellow).

4. Install a new 8E8908 Spring (orange) and the new 6T2293 Piston. The new arrangement has only one spring in "D" station.

5. Install a shim pack of .050" total thickness in the load piston using a combination of the existing and/or new parts required. This is an initial shim pack and will provide a reduced pressure close to the specification requirement.

6. Adjust the "D" station using the relief valve adjustment procedure shown in Service Magazine, March 4, 1991. The main relief valve pressure must be checked and adjusted, if necessary, before any adjustments are made to the dual stage relief valve setting at reduced pressure ("D" station). All pressure checks must be done with the engine at high idle and with transmission oil as close to operating temperature as possible.