my ryobi reciprocating saw is making a really loud grinding noise when i pull the trigger, sounds awful

Diagnosis

The loud, metallic grinding noise occurring immediately upon trigger pull on the Ryobi P519 is typically caused by the failure of the pinion gear or the drive gear assembly. In this specific reciprocating saw model, the motor rotates a small pinion gear that engages with a larger gear to drive the eccentric wobble plate. When the saw is pushed beyond its limits—specifically when using dull blades that cause the tool to bind or when cutting through dense materials without sufficient lubrication—the hardened teeth on these gears can chip, flatten, or shear off entirely. When the teeth are damaged, they no longer mesh smoothly. Instead, they "skip" or slide across each other at high RPMs, creating a violent grinding sound. If the noise is accompanied by a lack of blade movement (the motor spins but the blade doesn't move), the pinion gear has likely stripped completely. If the blade still moves but screams, you are dealing with partial tooth failure or a collapsed bearing in the gear housing that is allowing the shaft to oscillate off-center, causing the gears to clash unevenly.

How to Fix It

To resolve this, you must disassemble the gear housing to inspect and replace the damaged components. You will need a Phillips #2 screwdriver, a small flat-head screwdriver, and a set of needle-nose pliers.

1. Safety First: Remove the ONE+ 18V battery pack and ensure no blade is installed in the chuck to prevent accidental injury.
2. Case Disassembly: Remove the four long Phillips head screws located on the main body. Two are situated near the blade clamp assembly, and two are located toward the rear of the handle grip. Keep these screws organized, as they vary slightly in length.
3. Housing Separation: Carefully pry the two halves of the plastic housing apart. Be cautious not to snap the plastic alignment tabs. Lift the top shell slowly to avoid pulling the trigger switch wiring out of its socket.
4. Gear Inspection: Locate the motor shaft where it meets the gear assembly. Slide the gear housing assembly away from the motor. Inspect the small pinion gear on the end of the motor shaft and the larger drive gear. Look for "silvering" (worn-down metal), missing teeth, or metal shavings in the grease.
5. Component Replacement: If the pinion gear is stripped, slide it off the shaft. Install a replacement pinion gear, ensuring it is seated fully against the motor shoulder.
6. Lubrication: Clean out all old, contaminated grease and metal shards using a rag. Apply a generous amount of high-temperature lithium-based gear grease to the teeth of both the pinion and the drive gear. Do not overfill, as this can cause the housing to leak grease during operation.
7. Reassembly: Align the gear assembly back onto the motor shaft, snap the housing shells back together, and tighten the four long screws firmly, but do not over-torque them or you will strip the plastic threads.

If That Didn't Work

• Check the Eccentric Wobble Plate: If the gears look fine, the grinding may be coming from the wobble plate (the part that converts rotation to linear motion). If the bearing inside the wobble plate has failed, it will create a rhythmic grinding sound. You will need to replace the entire drive linkage assembly.
• Inspect the Motor Brushes: While the P519 is designed for longevity, worn carbon brushes can sometimes create a high-pitched electrical "screech" or grinding sound if they are sparking excessively against the commutator. Check the brushes for uneven wear or pitting.
• Verify Blade Clamp Tension: Check if the blade clamp mechanism is seized or grinding against the shoe. Spray the clamp area with a dry silicone lubricant to see if the noise persists without a blade installed; if the noise stops, the issue is external to the gearbox.
• Motor Bearing Failure: If the noise is coming from the rear of the tool rather than the front gear box, the motor's armature bearings have likely collapsed. This requires a full motor replacement, as the bearings on this specific model are not easily serviceable.

Heads Up

• Blade Quality: Always use high-TPI (teeth per inch) blades for thin metal and low-TPI for thick wood. Using a wood blade on metal causes extreme vibration that accelerates gear wear.
• Avoid "Forcing" the Cut: Let the tool do the work. If you have to lean your entire body weight into the saw to make it cut, your blade is dull. This pressure puts immense torque on the pinion gear, leading to the exact failure described above.
• Clear the Dust: Use compressed air to blow out the vents near the motor every few projects. Sawdust buildup inside the housing traps heat, which thins the gear grease and leads to premature metal-on-metal wear.
• Battery Heat: If the tool feels excessively hot near the handle, stop immediately. Overheating the motor can warp the shaft, causing the gears to misalign and grind.