2006/08/28 Caterpillar

Work Tool:

T15B (S/N: SLW1-UP)

T6B (S/N: KSK1-UP)

T9B (S/N: JAJ1-UP)

Service Magazine, SEPD0861, 30 10 2006, "The Idler Assembly for the Trencher Has Been Updated". Disregard this article. See the replacement article that follows.Service Magazine, SEPD0852, 28 08 2006, "The Idler Assembly for the Trencher Has Been Updated". Disregard this article. See the replacement article that follows.

Description of Change: In order to improve the function of the trencher, shims have been added to the idler group and cross-tubes on the idler assembly have been shortened.

Adaptable To: The updated idler group has become effective in production. The improvement is adaptable to all earlier trenchers. Use the following information and the procedure in order to upgrade the shaft assembly on earlier machines.

Table 1

Model	Adaptability	Effectivity
T6B	S/N:KSK1-461	S/N:KSK462-UP
T9B	S/N:JAJ1-1551	S/N:JAJ1552-UP
T15B	S/N:SLW1-557	S/N:SLW558-UP

Procedure to Modify the Trencher

1. Remove the pin from the master link in the chain. Pull apart the chain. Remove the chain from the idler pulley.

   Note: It is not necessary to fully remove the chain from the trencher.

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Illustration 1	g01299068
(1) Idler assembly

2. Remove the idler assembly (1) from the trencher's boom.

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Illustration 2	g01297823
(2) Bolt tubes (3) 291-2823 Shims (4) Side plates (5) Washers (6) Bolts (7) Nuts

3. Inspect the idler assembly and grind four bolt tubes (2) flush with the surface on each side. Paint the ground surfaces.

4. Clean all contact surfaces of the idler assembly.

5. Reassemble the idler into the boom with shims (3). Insert the shims inside the trencher's boom between the internal wall of the boom and the outside surface of the idler assembly. Use as many shims as necessary. Distribute the shims evenly to each side. A quantity of 0 to 6 shims may be necessary. Maintain a loose fit for adjustments.

6. Replace side plates (4), bolts (6), washers (5) and nuts (7). Carefully guide the bolts through the shims. Do not tighten.

7. Reassemble the chain.

8. Check the tension of the chain. The proper distance from the bottom surface of the boom tube to the top of the chain is 38 mm (1.5 inch) with a tolerance of +19 mm to - 6.5 mm (+.75 inch to -.25 inch). It may be necessary to use a grease gun to tension the chain using the grease cylinder inside of the trencher boom. Refer to Operation and Maintenance Manual, SEBU7757, "Chain - Inspect/Adjust".

9. Slide the side plates toward the front of the boom while tightening the bolts in order to take up the clearance in the bolt hole within the idler assembly tubes.

10. Torque the bolts to 100 N·m (74 lb ft) in a cross pattern. Repeated tightening may be necessary. Refer to Operation and Maintenance Manual, SEBU7757, "Chain - Inspect/Adjust".

11. Rotate the chain at least three times by using the host machine to operate the trencher.

12. Confirm proper chain tension before using the trencher.

    Note: The chain will stretch over time.