Disassembly Of Blower Drive Gear and Support Assembly For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

October 28, 2024

The blower drive gear and support assembly are responsible for driving the blower, ensuring that the proper amount of air is delivered to the engine for combustion. The drive gear and support must be carefully disassembled and inspected to maintain the efficiency and reliability of the engine’s air system. Disassembling this component involves working with precision gears, so care must be taken to prevent damage to the gear teeth and the support structure.


Safety Precautions:


  • Disconnect the Battery: As with any engine disassembly, ensure the battery is disconnected before working on the blower drive gear to prevent accidental engine start-up or electrical hazards.
  • Wear Protective Gear: Wear gloves and safety goggles to protect yourself from oil, grease, and debris that may be present during disassembly.
  • Ensure the Engine is Cool: Make sure the engine has fully cooled before starting disassembly to avoid burns from residual heat.

Disassembly Steps For The 71 Series Inline Blower Gear Drive (271, 371, 471, 671)


1. Remove the Blower (If Not Already Removed)


Before disassembling the blower drive gear, the blower itself must be removed from the engine.


  • Refer to Blower Disassembly Guide for detailed steps on removing the blower. Ensure the blower is fully disconnected from the drive system before proceeding to the drive gear.

2. Access the Blower Drive Gear Housing


The blower drive gear is typically housed behind a cover, which needs to be removed to access the gear and support assembly.


  • Remove the Drive Gear Cover:

    • Use a socket wrench to loosen and remove the bolts securing the blower drive gear cover to the engine. Carefully remove the cover to expose the drive gear.
    • Inspect the cover for signs of wear or damage. If the cover is warped or damaged, it may need to be replaced.

3. Disconnect the Blower Drive Gear


With the cover removed, the blower drive gear is now accessible for disassembly.


  • Mark the Gear Alignment:

    • Before removing the blower drive gear, mark its alignment with the other gears in the system. This will help ensure proper reinstallation and prevent timing issues when the engine is reassembled.

  • Loosen and Remove the Gear:

    • Use a gear puller or a socket wrench to carefully loosen and remove the blower drive gear from its shaft. Take care not to damage the gear teeth during removal.
    • If the gear is stuck due to age or heat, apply penetrating oil to help free it. Avoid using excessive force, as this can damage the gear teeth or shaft.

4. Remove the Blower Drive Support Assembly


Once the drive gear is removed, the support assembly can be detached from the engine block.


  • Remove the Mounting Bolts:

    • The blower drive support assembly is secured to the engine with a series of mounting bolts. Loosen these bolts using a socket wrench, and support the assembly as you remove the final bolts to prevent it from falling.

  • Carefully Remove the Support Assembly:

    • Lift the support assembly off the engine block, taking care not to disturb any adjacent components or drive mechanisms. Inspect the support for signs of wear, cracks, or damage.

5. Inspect the Drive Gear and Support Assembly


Once the blower drive gear and support assembly have been removed, it’s essential to inspect both components for wear and damage.


  • Inspect the Gear Teeth:

    • Carefully inspect the teeth of the blower drive gear for signs of wear, chipping, or misalignment. Damaged gear teeth can result in improper meshing with the other gears, leading to reduced blower performance.

  • Inspect the Support Assembly:
    • Check the blower drive support for cracks, wear at the mounting points, and any signs of misalignment. Replace or repair the support assembly if necessary to ensure proper blower operation.

  • Inspect Bearings and Bushings:
    • If the blower drive support contains bearings or bushings, inspect them for wear or damage. Worn bearings can lead to excessive play in the drive mechanism, reducing the efficiency of the blower system.

Reassembly Notes:


  1. Align the Drive Gear Properly:
    • When reinstalling the blower drive gear, ensure it is properly aligned with the marks you made during disassembly. Proper alignment is critical for ensuring that the blower is timed correctly with the engine.
    • Use a torque wrench to tighten the drive gear to the manufacturer’s specified torque settings.

  2. Secure the Support Assembly:
    • Reinstall the blower drive support assembly by aligning it with the mounting points on the engine block. Insert the mounting bolts and tighten them evenly to prevent misalignment.
    • If the support contains bearings or bushings, ensure they are lubricated and seated properly before reinstallation.

  3. Reinstall the Drive Gear Cover:
    • After the blower drive gear and support are secured, reinstall the drive gear cover. Ensure the cover is properly seated and that the bolts are tightened to the correct torque specification.

  4. Reinstall the Blower:
    • After the drive gear and support assembly are in place, follow the steps outlined in the blower reassembly section to reinstall the blower.

  5. Test the Drive System:
    • Once everything is reassembled, manually rotate the drive gear to ensure smooth operation without binding or noise. When running the engine, monitor the blower system for proper function and listen for any abnormal noises that could indicate misalignment or gear wear.

Inspection Tips:


  • Check Gear Alignment: Proper gear alignment is critical for ensuring smooth blower operation. After reassembly, verify that the gears are correctly meshed and that there is no excessive play or misalignment.

  • Look for Wear on Bearings and Bushings: If the blower drive support assembly contains bearings or bushings, inspect them regularly for signs of wear. Worn bearings can cause excessive vibration and reduce the efficiency of the blower system.

  • Monitor for Oil Leaks: Check around the drive gear cover for any signs of oil leaks. If leaks are present, they could indicate a problem with the gaskets or seals, which should be replaced immediately to prevent further issues.

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