2009/02/23 Caterpillar

Excavator:

385B (S/N: RCD1-UP; BKF1-UP; CLS1-UP; BKX1-UP)

385B L (S/N: MYA1-UP; FDL1-UP; ANS1-UP; BLY1-UP)

385C (S/N: KBC1-UP; KKK1-UP; JCM1-UP; MNZ1-UP)

385C L (S/N: EDA1-UP; KGB1-UP; SBE1-UP; T2E1-UP)

385C L MH (S/N: WAW1-UP)

385C FS (S/N: MMA1-UP; T2F1-UP; EAM1-UP)

5090B (S/N: CLD1-UP; SJY1-UP)

Mobile Hydraulic Power Unit:

385C MHPU (S/N: MSF1-UP; 0EM1-UP)

ReferenceRefer to Service Magazine, SEPD0851, 21 August 2006, "The Support May Crack in the Recoil Spring Gp" for additional information. Also refer to the Disassembly and Assembly Manual that is appropriate for your machine.

The new nonserviceable item 248-7308 Recoil Spring Gp is available for the replacement of the former nonserviceable item 297-9125 Front Idler Gp in the models that are listed. The serviceable components in the new recoil spring gp are listed in Table 1. The locations of the serviceable components are shown in Illustration 2.

The length of the stroke is increased for the spring in the new recoil spring gp. The longer stroke will absorb the force that is created by the tension of the track. The improved recoil spring gp prevents the failures of the support in the front idler group.

A chamfer has also been added on the edge of the plate for the track frame. The chamfer prevents interference between the idler group and the track frame, if the idler is in the full stroke position.

Install a new recoil spring gp, if the former recoil spring gp fails. Grind a chamfer on the edge of the plate in the track frame if a new recoil spring gp is installed. Refer to the following information.

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The recoil spring is located inside the track roller frame. This spring is compressed to a force of approximately 54000 kg (119000 lb). It is possible that the cracked section of the support will separate from the recoil assembly and cause severe injury or possible death. Make sure that the following procedure is thoroughly understood before any work is done.

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The spring of the recoil spring assembly is compressed under several tons of force. Do not attempt to compress or release the tension of the spring with the nut on the end of the retaining rod. Damaged threads on the retaining rod or nut can cause the assembly to come apart with force, resulting in injury or death.

Illustration 1	g01600153
Recoil Spring Gp And Front Idler Gp (A) Support (B) Front idler gp (C) Recoil spring gp

Illustration 2	g01600156
248-7308 Recoil Spring Gp (1) 168-6740 Washer (2) 168-6742 Plate (3) 248-7161 Rod (4) 248-7163 Spring (5) 297-9120 Support As (6) 297-9121 Support (7) 168-6741 Nut (8) 8T-6594 Bolt (D) 81 mm (3.2 inch) Reference dimension for the increased stroke (X) 1194.0 ± 1.0 mm (47.0 ± 0.04 inch)

Illustration 3	g01611513
Detail W From Illustration 2 (X) 1194.0 ± 1.0 mm (47.0 ± 0.04 inch)

Illustration 4	g01600233
Full Stroke Position (E) A chamfer is required.

Illustration 5	g01600253
View F-F From Illustration 4 (J) 125 mm (4.9 inch) (K) 35 mm (1.4 inch) (L) 42 mm (1.7 inch) (M) 145 mm (5.7 inch)

Illustration 6	g01600275
Section G-G And Section H-H From Illustration 5 (R) 8 mm (0.3 inch) (S) 5 mm (0.2 inch) (T) 8 mm (0.3 inch) by 16 mm (0.6 inch) Chamfer (U) 5 mm (0.2 inch) by 10 mm (0.4 inch) Chamfer

Grind chamfer (T) between point (D) and point (E). Grind chamfer (U) between point (B) and point (C). Also grind chamfer (U) between point (F) and point (G) .

Note: Finish grind all of the surfaces of the chamfers smoothly. The surfaces should not have any notches.

The assembled length of the recoil spring must be 1194.0 ± 1.0 mm (47.0 ± 0.04 inch). Refer to Illustration 2 and Illustration 3.