Repair of a Bevel Gear Case That Has a Damaged 3T-9389 Transmission Cover {3281} Caterpillar

Track-Type Skidder:

527 (S/N: 2RS1-UP; 3DS1-UP; 4NS1-UP; BDW1-UP)

Introduction

This Special Instruction provides the procedure for the replacement of a 3T-9389 transmission cover that has been damaged. The cover is a part of the 7T-6520 case assembly. The cover can be damaged during a failure of a bevel pinion bearing. The damaged 3T-9389 transmission cover should be replaced by a new cover. This procedure will allow you to verify that the bores for the bearings in the new cover are aligned with the bores for the bearings in the case. If the bores are not properly aligned, the cover must be repositioned on the case, and new holes must be machined in the case and in the cover for the dowels. If the bores for the bearings are not properly aligned, the life of the bearings will be reduced.

New bearings are also available. These bearings will provide improved life. A new tube assembly is also available. This will improve the flow of lubricating oil to the bearing that supports the bevel pinion.

Necessary Parts

Procedure for Replacement of Cover

1. Separate the transmission from the bevel gear case. Refer to Disassembly and Assembly, SENR9422, "527 Track-Type Skidder Power Train" for detailed instructions. Remove the gears and the bearings from the case. Clean the case so that the bores for the bearings are free of debris.

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Illustration 1	g00808137

2. Bolt the replacement cover to the transmission case. Use the original two dowels to locate the cover.

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Illustration 2	g00808016
(1) Dial indicator (2) Flat surface of the cover (3) Shaft that is perpendicular to the mounting surface

3. Measure the alignment for each pair of bores for the bearings with a dial indicator. Mount the dial indicator to a shaft that is perpendicular to the mounting surface on the flange of the case.
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   Illustration 3	g00808018

   1. Verify that the shaft is perpendicular to the case. Take a reading from the flat surface of the cover outside one of the bores with the dial indicator. Rotate the shaft that is holding the dial indicator in order to measure face runout (total indicator reading). The face runout must be less than 0.05 mm (0.002 inch). Otherwise, the case must be adjusted so that the case is perpendicular to the shaft.

   2. Position one of the bores in the case so that the bore is at the center of the axis of the shaft by using the dial indicator. Make adjustments until the total indicator reading is less than 0.025 mm (0.001 inch).
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   Illustration 4	g00808019

   3. Move the dial indicator to the corresponding bore in the cover. Measure the total indicator reading of the bore in the cover. The reading should be less than the amount specified in the following table.
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      Table 2

      Maximum Total Indicator Reading Between Opposing Bores
      Upper Transfer Gear ( 133.3 mm (5.248 inch) Bore)	Lower Transfer Gear ( 152 mm (5.984 inch) Bore)
      0.4 mm (0.016 inch) total indicator reading	0.2 mm (0.008 inch) total indicator reading

   4. Repeat steps 3.b and 3.c for the bores for the other transfer gear. If the measurements for the bores are within the specification, the cover does not need to be repositioned. Proceed to step 5.

4. If the total indicator reading for either bore in the cover is outside of the specification, then the cover must be repositioned. New holes for the locating dowels must be machined into the case and into the cover.

   1. Unbolt the cover and remove the two 5H-6202 dowels.

   2. Replace the cover and install four 0S-1585 bolts at equally spaced distances in order to hold the cover.

   3. Measure the total indicator reading by repeating steps 3.b through 3.d. If the measurements are outside of the specification, then loosen the bolts and reposition the cover. Tighten the bolts and measure the total indicator reading again. Repeat this step until the specified measurements are achieved.

   4. Install the remaining 0S-1585 bolts . Tighten the bolts to 105 ± 20 N·m (80 ± 15 lb ft).

   5. Obtain two dowels that are larger than the previous 5H-6202 dowels. The previous dowels are 1/2 inch dowels. The length of the new dowels should be 36 ± 4 mm (1.42 ± 0.16 inch). Machine the two existing holes that are in the case and in the cover for the new dowels. The diameter of the holes should be .04 ± .02 mm (0.002 ± 0.001 inch) smaller than the diameter of the dowels. This will provide the correct press fit. After the new holes are machined, remove the cover and install the two new dowels in the case. Two 5/8 inch 8B-6349 dowels may be used. The diameter of an 8B-6349 dowel is 15.718 mm (0.619 inch). The holes should be machined to 15.678 ± .02 mm (0.617 ± 0.001 inch).

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Illustration 5	g00814496

5. Prior to reassembly, drill and tap two 1/4-20 holes in the 3T-8527 cover . These threaded holes are used for clips that retain the 206-2080 tube assembly. Use illustration 5 in order to make a template. Place the template over the cover. Since the position of the holes in the cover only allow the cover to be correctly installed one way, align the existing 10.5 mm diameter holes. Mark the location of the two threaded holes and drill and tap the holes according to the illustration.

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Illustration 6	g00798977
Routing of the new tube for lubricating oil

6. Reassemble the bevel and transfer gear group. Use the parts that are listed in table 1. Refer to Disassembly and Assembly, SENR9422, "527 Track-Type Skidder Power Train" for detailed instructions. Remove the 6T-6819 tube as and replace the assembly with the 206-2963 tube assembly, the 052-0572 swivel tee , and the 206-2080 tube assembly. Use the bolts, washers, and clips to fasten the 206-2080 tube assembly to the 3T-8527 cover . This new tube will improve the flow of lubricating oil to the bevel pinion bearing.