there's a bad grinding noise from one rear wheel on my ryobi 40v, and it's hard to push.

Diagnosis

The grinding noise and increased rolling resistance on the RY401018 are typically caused by a failure in the rear wheel assembly, specifically involving the planetary gear set or the braking mechanism. Because this model utilizes a specific drive-train configuration to manage the 40V brushless power, any debris—such as a pebble, thick grass clumps, or a bent axle—can jam the internal gears. When the wheel is hard to push, it indicates a mechanical bind rather than an electrical failure. Another common culprit is the integration of the parking brake system. If the brake cable has stretched or the spring tension has weakened, the brake shoe may remain partially pressed against the wheel hub even when the handle lever is in the "disengaged" position. This creates a constant friction point, leading to the metallic grinding sound and a "heavy" feeling when pushing the mower forward. You can confirm this by lifting the rear of the mower and spinning the wheel; if the wheel stops abruptly or makes a rhythmic scraping sound, the issue is internal to the hub or the brake assembly.

How to Fix It

To resolve the grinding and resistance, follow these steps to inspect and clear the wheel assembly:

1. Safety First: Remove the 40V battery pack immediately to ensure the mower cannot accidentally engage.
2. Elevate and Isolate: Prop the rear of the mower up on a sturdy block or workbench so the problematic wheel is suspended in the air.
3. Clear External Debris: Use a stiff brush or compressed air to clear the gap between the wheel rim and the mower deck. Look for wrapped-up twine, long grass stems, or pebbles lodged in the axle groove.
4. Inspect the Brake Lever: Ensure the red parking brake lever on the handle is pushed completely forward. While holding the lever, check the cable housing near the rear wheel to see if the cable is sliding freely. If the cable is frayed or kinked, it will prevent the brake from releasing.
5. Wheel Removal: Use a socket wrench to remove the center bolt of the noisy wheel. Carefully slide the wheel off the axle.
6. Gearbox Inspection: Inspect the planetary gear teeth on the axle. If you see metal shavings or a chipped tooth, the gear set is compromised. If it is simply dirty, clean the gears with a degreaser and apply a small amount of lithium-based grease.
7. Reassembly: Slide the wheel back on, ensuring the keyway is properly aligned, and tighten the center bolt firmly to prevent the wheel from wobbling and wearing down the axle.

If That Didn't Work

• Replace the Wheel Assembly: If the grinding persists after cleaning, the internal bearings or the planetary gear carrier have likely failed. Since these are sealed units, you cannot easily replace a single bearing. Order a replacement rear wheel assembly specifically for the RY401018 model and swap the entire unit.
• Adjust the Brake Cable: If the brake is partially engaged, the cable may have stretched. Loosen the cable clamp at the wheel end, pull the cable slightly tighter (about 1/8th of an inch), and retighten the clamp to ensure the brake shoe fully retracts.
• Axle Alignment Check: Check if the axle is bent. Place the mower on a perfectly flat surface and spin the wheel slowly. If the wheel "wobbles" or oscillates side-to-side, the axle is bent, which causes the wheel to rub against the chassis, creating a grinding sound. This requires a full axle replacement.
• Lubricate the Hub: In cases of light grinding due to dry friction, spray a high-quality silicone lubricant or WD-40 Specialist Penetrant into the hub assembly. Spin the wheel repeatedly to work the lubricant into the gear teeth.

Heads Up

• Avoid Over-Greasing: Do not pack the wheel hubs with excessive grease, as this attracts dirt and grit, which acts like sandpaper on the plastic and metal gears, accelerating wear.
• Check Tire Pressure: If your model has pneumatic tires, ensure they are inflated to the specified PSI; an under-inflated tire can rub against the frame, mimicking a mechanical grinding noise.
• Seasonal Cleaning: At the end of every mowing season, use a pressure washer or hose to clear the under-deck and wheel axles to prevent organic matter from hardening into "concrete" around the bearings.
• Battery Storage: Always remove the 40V battery before performing any mechanical work on the wheels to prevent accidental activation of the brushless motor.