Cards

Replacing replacement of parts for Kubota

Upload a Design

Product

GEARBOX

Buy now and get a discounted price.

Get Up To 10% OFF

Get Notified
PRR TRACTOR PART LIMITED PARTNERSHIP Email: [email protected]

Heavy-Duty Agricultural Gearboxes

Specialized replacement solutions for Kubota and global tractor implements. Engineered for durability, precision, and seamless power transmission.

Technical Specifications

Based on standard Kubota M/L/B Series Implement Requirements

Parameter Specification Data / Standard
Applicable HP Range 35 HP - 85 HP (Continuous Duty)
Input Shaft Speed (PTO) 540 RPM (Standard) / 1000 RPM (Optional)
Gear Ratio Availability 1:1.46 (Increaser) / 1:1.93 (Increaser) / 1.5:1 (Reducer)
Input Spline Type 1-3/8" - 6 Spline (Standard SAE J1170)
Output Shaft Design Tapered Spline with Castle Nut / 12-Spline / Keyed
Gear Material Hardness HRC 58-62 (Carburized Alloy Steel)
Housing Construction Ductile Iron QT450-10 (High Shock Resistance)
Lubricant Capacity 1.2 Liters (Recommended SAE 90 / 85W-140)
Noise Level < 85 dB at Full Load
Operating Temperature -20°C to +120°C
Kubota Replacement Gearbox

PRR Advantage: OEM Quality, Better Price

Our aftermarket parts are manufactured to strict ISO standards. We guarantee 100% compatibility with original Kubota mounting points while offering a 40% cost saving compared to dealership prices.

What is an Agricultural Gearbox?

An agricultural gearbox is the critical mechanical interface that transfers power from the tractor to the implement. It connects directly to the PTO Shaft (Power Take-Off), converting the tractor's engine power into the specific torque and speed needed for mowers, rotary tillers, and post-hole diggers.

Key Component Breakdown

1. Input & Output Shafts Typically made from 20CrMnTi steel. The input shaft connects to the PTO driveline, while the output shaft drives the implement's blades or chain.
2. Bevel Gear Set The heart of the box. These precision-cut gears change the direction of power by 90 degrees and determine the speed ratio (speed up or slow down).
3. Bearings High-load tapered roller bearings support the rotating shafts, ensuring stability under the intense vibration of field work.
4. Housing (Casing) A heavy cast iron shell that holds oil for lubrication, dissipates heat, and protects internal parts from dust, mud, and impact.

Working Principle: The Physics of Power

The agricultural gearbox operates on the principle of Torque Conversion and Directional Change. It is not merely a connector; it is a transformer of energy.

  • Power Entry (The Drive): Kinetic energy enters via the PTO shaft at a standardized speed (usually 540 RPM). This rotates the input pinion gear.
  • Transmission (The Mesh): The input pinion meshes with the crown gear (ring gear). Because these gears are bevelled (angled), they transfer the rotation 90 degrees—turning a horizontal shaft rotation into a vertical one (crucial for rotary mowers).
  • Ratio Modulation:
    Speed Increaser: If the input gear is larger than the output gear, the blade spins faster than the tractor engine (e.g., for finishing mowers).
    Speed Reducer: If the input gear is smaller, torque is increased while speed drops (e.g., for rototillers breaking hard soil).
Internal Gear Mechanism

Internal Bevel Gear Configuration

Professional Maintenance & Care Guide

1. Oil Management

Initial Break-in: Change the oil after the first 50 hours of use to remove metallic shavings from gear seating.

Routine: Change every season or 500 hours. Use SAE 90 or 80W-90 Gear Oil. Do not overfill, as pressure build-up can blow out seals.

2. Seal & Breather Check

Seals: Inspect input/output shafts for wetness. Grass or wire wrapping around the shaft is the #1 cause of seal failure—clean this area daily.

Breather Plug: Ensure the breather plug is not clogged with mud. A clogged breather causes internal pressure to rise, forcing oil past the seals.

3. Mounting & PTO

Hardware: Check mounting bolts before every heavy use. Vibration loosens nuts quickly.

PTO Alignment: Ensure the PTO shaft is not too long (bottoming out) or operating at an angle greater than 25 degrees, which destroys gearbox bearings.

How to Select the Right Gearbox

Choosing the wrong gearbox leads to catastrophic failure. Follow this 4-step engineering checklist:

1. Horsepower Rating (HP)

Always choose a gearbox rated higher than your tractor's PTO HP. If your tractor is 40HP, select a 50HP or 60HP gearbox to handle shock loads.

2. Gear Ratio Calculation

Check the implement requirements.
1:1.47 = Output spins faster (Mowers).
1.5:1 = Output spins slower (Tillers/Post Hole Diggers).

3. Shaft Configuration

Measure carefully:
Input: Usually 1-3/8" 6-Spline.
Output: Smooth (keyed) vs. Splined (12-tooth). A mismatch makes installation impossible.

4. Rotation Direction

Stand behind the tractor. Does the implement need to spin Clockwise (CW) or Counter-Clockwise (CCW)? This is determined by internal gear placement.

FAQ

Are your gearboxes shipped pre-filled with oil?

No. For safety and shipping regulations, all gearboxes are shipped dry. You must fill them with the recommended SAE 90 gear oil to the correct level before operation, otherwise catastrophic damage will occur immediately.

How do I check if the gearbox is compatible with my specific Kubota model?

You need to check the bolt mounting pattern (distance between holes) and the shaft type. While we list compatible series (like L or B series), physically measuring your broken unit is the safest method. Contact us for a technical drawing comparison.

What is the difference between a shear bolt and a slip clutch gearbox protection?

A shear bolt is a simple bolt designed to snap if you hit a rock, disconnecting power. A slip clutch uses friction plates to "slip" under load and then re-engage. Gearboxes can be used with either, but the protection is usually on the PTO shaft, not inside the box.

Why is my gearbox leaking oil from the vent plug?

This usually means the gearbox is overfilled. As oil heats up, it expands. If there is no air gap, it forces oil out of the breather. Check the level plug; oil should just barely reach the threads of the check port.

Can I use a higher HP gearbox on a smaller tractor?

Yes, absolutely. Using a 60HP gearbox on a 30HP tractor adds durability and safety factor. However, never do the opposite (using a 30HP gearbox on a 60HP tractor), as the torque will destroy the gears.

Do you sell replacement internal parts like gears and shafts separately?

Yes. Unlike many suppliers who only sell full units, PRR Tractor Part stocks individual bevel gear sets, shafts, and seal kits, making long-term repair economical.

What is the typical lifespan of these replacement gearboxes?

With proper maintenance (oil changes and seal checks), our gearboxes typically last 800-1200 hours of operation, which is comparable to OEM lifespans.

How tight should the mounting bolts be?

For standard M12 or M14 bolts used on these boxes, torque them to 80-100 Nm. We strongly recommend using blue Loctite (thread locker) to prevent vibration from loosening them.

Is this gearbox suitable for reversible operation?

Most standard agricultural gearboxes are designed for one-way rotation. Running them in reverse for long periods can damage the oil seal lip design. Check specific model specs if bi-directional rotation is needed.

What is your warranty policy for international orders?

We provide a 12-month warranty on the main housing and gear set against manufacturing defects. We can ship replacement parts via air freight if a valid defect is confirmed.

gearbox

At PRR TRACTOR PART, we understand that downtime is the enemy of productivity. Our replacement gearbox series for Kubota is engineered to endure, having passed rigorous 1.5x dynamic load testing to ensure peak performance under pressure. Designed for perfect bolt-on compatibility with original mounting points, we empower global distributors to reduce procurement costs by over 40%