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Main Pump: Inspection

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  1. Measure depth of main pump body gear cavity at location shown (dimension "A"). See Fig 1. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If dimension is exceeded, replace main pump body.
  2. Measure inside diameter of main pump body gear cavity (dimension "B") at several locations. See Fig 1. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If specification is exceeded, replace main pump body.
  3. Measure outside diameter of the driven gear at several locations. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If minimum specification is not met, replace driven gear.
  4. Measure distance between flats of the drive gear as shown (dimension "A"). See Fig 2. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If maximum specification is exceeded, replace drive gear.
  5. Align the drive gear and driven gear with the main pump, so punch marks are in the same position as when removed. Install gears into main pump body. Using a feeler gauge, measure clearance between driven gear outer edge and main pump body. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If maximum specification is exceeded, replace drive gear, driven gear and main pump body.
  6. Using a feeler gauge, measure clearance between driven gear inner edge and main pump body crescent. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. Hold a straightedge across main pump body and drive gear. Measure clearance between the drive gear and the straightedge. Compare measurement to specifications. If maximum specification is exceeded, replace drive gear, driven gear and main pump body.
  7. Remove drive gear and driven gear from main pump body. Invert pump body and check bushing for damage or wear. Measure inside diameter of bushing. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If bushing is worn or damaged, or if inside diameter exceeds specification, replace main pump assembly.
  8. If dowel pins are damaged, remove dowel pin from main pump body using gentle tapping pressure. Using a Dowel Pin Installer (J-43779) or equivalent, gently tap NEW dowel pin into place. Use care to avoid marring machined surface of main pump body. Dowel pin should be installed to a height of .42-.44" (10.7-11.3 mm).
  9. Inspect wear plate for damage. Wear plate must not be scored, nicked or grooved. Measure thickness of wear plate in gear wear area, using a micrometer. Compare measurement to specifications. See FRONT SUPPORT & MAIN PUMP MODULE SPECIFICATIONS  table under TRANSMISSION SPECIFICATIONS. If thickness is less than specification, replace wear plate.
Fig 1: Measuring Main Pump Body Cavity & Inside Diameter
G00092388Courtesy of GENERAL MOTORS CORP.
Fig 2: Measuring Drive Gear Diameter Between Flats
G00092392Courtesy of GENERAL MOTORS CORP.
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