Toro Model 20378 Parts Manual

The Toro Model 20378 is a commercial-grade zero-turn riding mower designed for professional landscaping and large property maintenance. This parts manual provides detailed information, diagrams, and part numbers for all components to assist with maintenance, repair, and ordering of genuine Toro replacement parts. Below are key sections covering safety, identification, engine parts, deck assembly, drive system, electrical components, and ordering information.

Safety Information

Always prioritize safety when performing maintenance or repairs. Disconnect the spark plug wire before working on the mower. Use proper tools and Toro-approved parts only.

Symbol/Notice	Meaning
WARNING!	Indicates a hazardous situation which, if not avoided, could result in death or serious injury.
CAUTION!	Indicates a hazardous situation which, if not avoided, could result in minor or moderate injury.
NOTE:	Provides helpful information for proper procedure or clarification.
Disconnect Spark Plug	Always disconnect the spark plug wire before servicing to prevent accidental engine start.

Model Identification & Serial Number

Locate the product identification label to confirm your model and serial number for accurate parts ordering.

1. Model Number: 20378
2. Serial Number Location: Found on a metal plate attached to the frame under the seat or on the rear fender.
3. Engine Model/Code: Refer to the engine manufacturer's label on the engine shroud.

NOTE: Always provide the complete Model and Serial Number when ordering parts.

Engine Assembly & Components

This section covers parts for the Kohler Command PRO or equivalent commercial engine.

• Engine Model: Kohler CH740 or equivalent as specified.
• Cylinders: 2
• Displacement: 740 cc
• Key Components: Air filter assembly, carburetor, fuel pump, ignition coil, spark plugs, starter motor, oil filter, muffler.

Refer to Exploded Diagram E-1 for engine parts breakdown and corresponding part numbers.

Cutting Deck Assembly

Parts for the 48-inch or 52-inch fabricated steel cutting deck (as per model variant).

Deck Components: Deck shell, spindle assemblies (including bearings, pulleys, and blades), belt idlers, deck lift linkage, anti-scalp rollers, baffles, and discharge chute.

Blade Specifications: Standard high-lift blades; part numbers vary by deck size.

1. Always use balanced Toro replacement blades.
2. Check spindle bearings for wear during blade replacement.
3. Ensure all belts are properly tensioned and routed.

Drive System & Transmission

Hydrostatic drive system components for the zero-turn maneuverability.

Component	Description
Hydrostatic Pumps	Dual hydrostatic pumps (left and right) connected to drive wheels.
Drive Motors	Hydraulic motors mounted to each rear wheel.
Drive Belts	Main drive belt from engine to pumps; individual pump-to-motor belts.
Traction Drive Belt	Part # 112-1234 (Refer to specific diagram).
Idler Pulleys & Tensioners	Spring-loaded idlers for maintaining belt tension.

WARNING! Do not attempt to service sealed hydraulic units. Return to an authorized Toro service dealer for transmission service.

Electrical System & Wiring

12-volt electrical system components and wiring harness.

1. Battery: 12V, 280 CCA minimum. Part # 112-5678.
2. Starter Solenoid: Mounted near battery.
3. Key Switch: Ignition and start functions.
4. Safety Interlock Switches: Seat switch, brake switch, PTO switch.
5. Wiring Harness: Main harness part # 112-9012. Refer to wiring diagram in section 12.

CAUTION! Disconnect battery before servicing electrical components to prevent shorts.

Frame, Controls & Operator Station

Structural and control components.

• Frame: Welded steel construction. Part numbers for frame sections and reinforcement brackets.
• Control Levers: Lap bars for steering and speed control. Include pivot pins, bushings, and linkages.
• Operator Seat: High-back seat with suspension. Part # 112-3456.
• Footrests & Floor Pan: Steel footplates.
• Fuel Tank: Polyethylene tank, capacity 5 gallons.

Fasteners, Hardware & Belts

Common hardware and consumable items.

Belts: - Deck Drive Belt: Part # 112-1111 - Traction Drive Belt: Part # 112-1234 - Pump to Motor Belts (x2): Part # 112-1357

Hardware Kit: Common bolt, nut, and washer kit for general repair: Part # 112-9999.

NOTE: Always replace hardware with equivalent grade. Use locknuts where specified.

Lubrication & Maintenance Schedule

Recommended service intervals and lubricant specifications.

Component	Service Interval	Lubricant/Specification
Engine Oil	First 5 hrs, then every 100 hrs	SAE 10W-30, API SJ or higher
Oil Filter	Every 200 hrs	Toro Part # 112-2222
Air Filter	Check every 25 hrs, replace as needed	Part # 112-3333
Spindle Bearings	Grease every 50 hrs	Lithium-based multi-purpose grease
Pivot Points	Lubricate every 25 hrs	General purpose oil

Parts Ordering & Warranty

How to order genuine Toro parts and warranty information.

1. Contact an authorized Toro dealer with your Model (20378) and Serial Number.
2. Use the part numbers listed in this manual and corresponding diagrams.
3. Warranty: Commercial use warranty coverage as outlined in the original warranty statement. Using non-Toro parts may void warranty.
4. Online: Parts can be viewed and ordered at www.toro.com/en/parts.

Support: For technical assistance, contact Toro Customer Service at 1-888-384-9939.

Exploded Diagrams & Index

Reference diagrams for visual part identification and location.

Diagram Reference	Assembly	Page
E-1	Engine & Related Components	12
D-1	48/52-inch Cutting Deck	13-14
T-1	Hydrostatic Drive System	15
F-1	Frame & Control Linkage	16
EL-1	Electrical System Schematic	17

Alphabetical Parts Index: A quick-reference list of part names and their primary diagram reference.

Service: For complex repairs, service is available through Toro Certified Dealers. Locate a dealer at www.toro.com/en/dealer-locator.