Timing gear1/8/2024 "Flowchart for Repair or Replacement of Gear Train and Engine Timing - Part 1 of 3"įigure 7. To determine if repair is possible or replacement is necessary, perform the following procedure. Repair or Replacement of Gear Train and Engine Timing See FigureĪn "out of time" engine may result in valve-to-piston dome contact, a no-start condition or loss of power. Section 1.24.1 Therefore, when the engine is properly timed, the timing marks on the various gears will match. The crankshaft and camshaft gears can only be mounted in one position as they are both keyed to their mating parts. The correct relationship between the crankshaft and the camshaft must be maintained to properly control the opening and closing of the intake and exhaust valves, and the operation of the fuel injectors and to help maintain engine balance. The hole in the engine block is connected to the main oil gallery. The adjustable idler gear assembly is pressure-fed by an oil gallery in the gear case that indexes with a hole in the engine block. These two holes are connected to the main oil gallery. Gear Train Lubricating Oil Hole Locations "Gear Train Lubricating Oil Hole Locations"įigure 4. The bull gear and camshaft idler gear are pressure-fed lubricating oil through two holes in the bull gear recess area of the engine block. The gear train is lubricated by oil splash. A rattling noise usually indicates excessive gear lash whereas a whining noise indicates too little gear lash. Therefore, when noise develops in a gear train, the gear case cover should be removed and the gear train and its bearings inspected. Gear train noise is usually an indication of excessive gear lash, chipped, pitted or burred gear teeth or excessive bearing wear. The backlash between the various mating gears in the gear train should be 0.051 - 0.229 mm (0.002 - 0.009 in.) and should not exceed 0.305 mm (0.012 in.) backlash between worn gears. Therefore, it is not necessary to align these gears in any particular position during their installation. There are no timing marks on the drive gears for the fuel pump, air compressor and power steering pump, water pump or accessory drive pulley. When assembling the engine, work from the crankshaft timing gear to the camshaft drive gear and line up the appropriate symbols on the gears as each gear assembly is installed on the engine. The symbol system of marking the gears makes gear train timing a comparatively easy operation.
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