How to Replace the Gear Case on a DeWALT Angle Grinder (Model D28402)

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The gear case assembly consists of the front gear housing, the gearing, the spindle, the spindle bearing, and the lock button. The bad news? The case is factory-assembled as a single unit, which means, if any of the individual components fail, the entire assembly must be replaced.

The good news is that replacing the entire gear case assembly is very easy to do, especially when you follow these step-by-step instructions. This article will show you how to replace the gear case assembly on a DeWALT D28402 angle grinder.

Let's get started.

  REMOVING THE GEAR CASE [top] 1. Remove the side handle.

Unscrew and detach the side handle from the grinder.

  2. Remove the guard.

Raise the guard latch.

Rotate the guard until the lugs disengage.

Remove the guard from the grinder.

  3. Remove the top half of the handle assembly.

Remove the (5) retaining screws.

Remove the top half of the handle assembly.

  4. Separate the handle from the field case.

Remove the paddle assembly.

Remove the lock-on button assembly.

Separate the handle from the field case.

  5. Disengage the motor brushes.

Use long-nosed pliers to detach the brush wire from the terminal.

Use long-nosed pliers to lift the brush spring away from the brush arm.

Lift (rotate) the brush arm assembly away from the armature.

Repeat this step to disengage the second motor brush (on the opposite side of the grinder).

  6. Remove the separator/fan.

Press and hold the spindle-lock button (on the gear case) to prevent the motor from spinning.

The separator fan is REVERSE-THREADED; rotate the fan in a CLOCKWISE direction to loosen it.

Remove the fan from the armature shaft.

  7. Remove the gear case assembly.

Remove the (4) gear case retaining screws.

Using a flat-blade screwdriver, gently pry the gear case assembly away from the field case.

Slide the gear case assembly (and armature) out of the field case.

  8. Detach the armature from the gear case.

SPECIFIX: During factory assembly, the armature is pressed into a bearing within the gear case assembly. The two components can generally be separated by hand. However, particularly "stubborn" connections may be broken by tapping the rear shaft of the armature with a rubber mallet.

Firmly grasp the components on each side of the connection (one hand on the armature; one hand on the gear case).

Apply slight outward pressure (as if breaking a wooden branch) while pulling the two components away from each other.

Detach the armature assembly from the gear case.

  INSTALLING THE NEW GEAR CASE [top] 9. Attach the armature to the new gear case.

Insert the armature assembly into the new gear case (rotate the assembly until the pinion gear engages the bevel gear).

Align the tabs on retainer plate with the slots on the gear case.

Tap the rear shaft of the armature with a rubber mallet (as-needed) to seat the bearing into the gear case.

  10. Transfer the gear case cover.

Remove the (4) retaining screws from the gear case cover (on the old gear case assembly).

Remove the gear case cover from the old gear case assembly.

Inspect the gasket in the gear case cover; replace as necessary.

Liberally apply grease to the exposed gears (in the new assembly).

Install the gear case cover onto the new gear case assembly.

Secure the gear case cover with the screws.

  REASSEMBLING THE UNIT [top] 11. Reinstall the gear case (and armature) assembly into the field case.

Slide the gear case (and armature) assembly into the field case.

Secure the gear case with the (4) screws.

  12. Reinstall the separator/fan.

Press and hold the spindle-lock button (on the gear case) to prevent the motor from spinning.

The separator/fan is REVERSE-THREADED; rotate the fan in a COUNTERCLOCKWISE direction to secure it to the armature.

  13. Re-engage the motor brushes.

Lower (rotate) the brush arm assembly into position above the armature.

Use long-nosed pliers to re-engage the brush spring.

Reattach the brush wire.

Repeat this step to re-engage the second motor brush (on the opposite side of the grinder).

  14. Reattach the handle assembly to the field case.

Connect the lower half of the handle to the field case (when properly aligned, the two components should “snap” together).

Tuck the wires into the designated channels inside the handle.

  15. Reinstall the lock-on button.

One side of the lock-on button contains a small tab. This tab should be installed facing the armature.

Install the lock-on button into the handle.

  16. Reinstall the paddle assembly.

Install the paddle assembly into the handle; ensure that the “tail” is positioned above the switch button, and the “fulcrum” is seated within the recess in the handle.

  17. Reinstall the top half of the handle assembly.

Partially install the top half of the handle assembly.

Align the posts (on the paddle and the lock-on button) with the recesses in the top of the handle.

Before securing the handle with the screws, test the paddle and the lock-on button for proper functionality.

Secure the handle with the screws.

  18. Reinstall the guard.

Install the guard onto the grinder.

Press and rotate the guard to engage the lugs.

Lower the latch to secure the guard.

    19. Reinstall the side handle.

Thread the side handle onto the gear case assembly.

You can't place a value on a job well done, unless you did it yourself. (Which you did.) Now you can place that value back into your own pocket. (Or into your business.) Not only did you refine your grinder at a fraction of the cost of replacement; you have expanded your skills far beyond the daily grind.

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