TUBE AS 7C7234 - Caterpillar

Introduction
This Special Instruction provides the necessary information required to add additional bolts to the cover/case of the pump drive assembly to minimize oil leaking and bolt loosening.Additional bolts will increase the clamping force of the joint and help prevent oil seepage. Care must be taken to properly position the bolts so that they are located in area with adequate material. It is important that the bolts do not extend through the flange of the cover and case or enter the internal reservoir of the pump drive.Two machining options are available for making the modification. The options are to use a milling machine or a radial arm drill press for drilling, counter boring, spot facing, and tapping for the extra bolts.Reference: Service Manual, Parts Manual, and Service Magazine Article entitled New Lines Bracket Prevents Bolts Loosening In Pump Drive in the January 27, 1992 issue.Installation
1. Disconnect and remove the hydraulic lines and pumps from the pump drive. Refer to the Service Manual for the procedure to use.2. Remove the pump drive from the excavator. Refer to the Service Manual for the procedure to use.3. Decide on the machining method to be used. For milling operations use the procedure called Milling. For drilling, use the procedure called Radial Drilling.Milling
1. Locate the pump drive on the milling machine table and clamp in position. Block the assembly between the case and the table to clear the spider retaining bolt and plate before clamping. Use parallel blocks between the machined mounting surface of the case and table.
Fig. 1.2. Locate the new bolt holes in the case and cover as shown in Fig. 1.3. Center drill each new hole location to a starting depth.4. Tap drill the eight new holes with a 8.20 mm (.323 in) diameter drill to a depth of 28.0 mm (1.10 in).5. Counterbore the cover using a 10.50 mm (.413 in) diameter drill to a depth of 16.0 mm (.63 in).6. Tap the eight case holes 3/8-16-2B to a depth of 21.0 mm (.83 in).7. Spotface the cover 21.0 mm (.83 in) diameter to a clean up depth.8. Clean all bolt holes thoroughly with low pressure compressed air.9. Install eight (new) 0S1588 Bolts and 5M2894 Washers into the housing and tighten to 57 7 N m (42 5 lb ft).10. Install the pump drive, pumps and piping onto the machine. Refer to the Service Manual for the procedure to use.Radial Drilling
1. Locate the pump drive assembly on the table of the radial arm drill press. Block the assembly between the case and the table to clear the spider retaining bolt and plate assembly before clamping to the table. Use parallel blocks between the machined mounting surface of the case and table. 2. Apply bluing (dye) to the flange area to be layed out.
Fig. 2. 3. Use a Vernier caliper to scribe a line 12.70 mm (.500 in) from the outer edge of the flange. 4. Use a Vernier caliper to scribe an intersecting line located from the existing