The ROP Shop Electric PTO Clutch for Ariens 4387900, 04387900, Gravely 4387900, 04387900 Lawn

What It Is

The ROP Shop Electric PTO Clutch (part numbers 4387900, 04387900) engages and disengages the mower blades via an electromagnetic coil. It’s a direct replacement for the OEM clutch on select Ariens and Gravely zero-turn and lawn tractors.

Fitment & Compatibility

Before buying, confirm your machine uses a 12V electric PTO clutch with a 1-inch shaft and three-bolt mounting pattern (bolt circle diameter ~3.25 inches). This clutch fits Ariens and Gravely models that originally used OEM part 4387900 or 04387900, including many Zoom and ZT series zero-turns. Check your deck size (typically 42–60 inches) and engine horsepower (20–27 HP) – it’s not for smaller push mowers or older mechanical PTOs. Measure your existing clutch’s outside diameter (should be about 6 inches) and pulley width (approx. 2 inches) to verify. Always cross-reference with your mower’s model number and serial number on the manufacturer’s parts diagram.

Key Things to Know

• Quality: Aftermarket unit; reviews are limited (4 ratings, 5.0 stars) but positive. Expect similar lifespan to OEM if properly installed, but no warranty beyond basic return policy.
• Installation: Moderate difficulty – requires removing the mower deck, disconnecting wiring, and unbolting the old clutch. You’ll need a puller tool to remove the clutch from the crankshaft; don’t pry it off. Torque the center bolt to 40–50 ft-lbs.
• Common gotchas: The air gap (0.012–0.020 inches between rotor and armature) may need adjustment after installation. If the clutch doesn’t engage, check for a blown fuse or loose ground wire. Wiring colors may differ from OEM – note polarity before connecting.
• Noise: Some users report a slight whine during engagement; this is normal for aftermarket clutches and doesn’t affect performance.

Should You Buy It

If you need a budget-friendly replacement for an Ariens/Gravely 4387900 clutch and you’re comfortable with basic mechanical work (or have a shop install it), this is a solid choice. Skip it if you want OEM peace of mind or need a clutch for a different brand – fitment is narrow.