Tractor PTO Spline Shaft | 6 and 21 Spline Options

Product Overview

The spline is where everything starts. Before the cross-bearings absorb angular changes, before the telescoping tubes adjust for distance, the very first mechanical connection between your tractor and PTO driveline happens at the splined interface. Get the spline wrong and nothing else matters. The Tractor PTO Spline Shaft for Agricultural Machinery is built around getting that interface right, with precision-machined spline yokes that fit 6-spline, 21-spline, and metric 8-spline PTO stubs used on tractors sold across the Korean market.  

Why Spline Configuration Matters So Much

The spline transmits all of the tractor's PTO torque through interlocking teeth on the yoke bore and the PTO stub. A 6-spline interface has six teeth distributing the load, while a 21-spline interface spreads the same torque across twenty-one teeth, resulting in lower stress per tooth. This is why higher-HP, 1000-RPM PTO outputs typically use 21-spline connections. Choosing the Tractor PTO Spline Shaft with the correct tooth count and diameter ensures a tight fit that doesn't wear, rattle, or slip during operation.

6-Spline vs. 21-Spline: Quick Reference

Spline Adapters and Configuration Options

Not every tractor-to-implement combination uses the same spline on both ends. That's where adapters come in. The Tractor PTO Spline Shaft for Agricultural Machinery is available in several spline configurations to handle mismatched equipment:

6-Spline Adapter

Connects a 6-spline PTO stub to a 6-spline implement input. This is the most common configuration for 540 RPM applications on tractors under 75 HP. The adapter yoke is zinc-coated for corrosion resistance and designed to withstand external impacts during normal field operation.

21-Spline Adapter

For 1000 RPM PTO outputs. The finer tooth pitch of the 21-spline interface requires tighter manufacturing tolerances, and our CNC-machined spline bores are held to ISO 500 standards. The Tractor PTO Spline Shaft with 21-spline yokes is typically paired with higher-HP implements like large rotary cutters, round balers, and high-output feed mixers.

Metric 8-Spline Options

Japanese-market tractors from Kubota, Yanmar, and Iseki often use metric spline dimensions (8-spline 38x32, 42x36, or 48x42 mm). We stock these alongside the standard inch configurations so Korean operators using Japanese compact tractors don't need separate adapter bushings.

How to Identify Your Spline Configuration

If you're not sure which spline shaft configuration your tractor uses, here are three quick identification methods:

Method 1: Count the Teeth

Look at the tractor PTO stub end-on and count the raised teeth. Six large teeth = 6-spline. Twenty-one fine teeth = 21-spline. This is the fastest way to identify the configuration and it doesn't require any tools.

Method 2: Measure the Diameter

Use a caliper across the outer diameter of the PTO stub. Common readings: 34.9 mm (1-3/8") for both 6 and 21 spline, 44.5 mm (1-3/4") for heavy-duty 6 or 20 spline, or metric sizes like 38 mm for Japanese compact tractors.

Method 3: Check the Tractor Manual

The operator's manual specifies the PTO spline type. If you've lost the manual, our Korean support team can look up the spline configuration by tractor make and model. Send us your tractor details and we'll confirm the correct Tractor PTO Spline Shaft specification within one business day.

Spline Wear: Causes, Signs, and Prevention

Spline wear is the gradual loss of material on the interlocking teeth of the yoke bore and PTO stub. Once wear passes a critical point, the connection develops play that accelerates further damage and can lead to rounding off of the teeth entirely. Here's what to watch for:

• ◉ Clicking or clunking when the PTO engages or disengages, caused by play between worn teeth
• ◉ Difficulty sliding the yoke onto the PTO stub, often from burrs formed on worn tooth edges
• ◉ Visible shiny wear marks on the spline teeth when the yoke is removed
• ◉ Rotational play when you grip the yoke and try to twist it relative to the PTO stub

Prevention is straightforward: apply anti-seize compound to the spline teeth each time you connect or disconnect the Tractor PTO Spline Shaft for Agricultural Machinery. This lubricates the interface and prevents corrosion bonding between the steel surfaces. A thin coat is sufficient. Most operators in Korea skip this step, and most operators in Korea replace yokes more often than they should.

Companion Products

Spline Shaft and Gearbox Interface

The implement end of the Tractor PTO Spline Shaft connects to an agricultural gearbox that converts PTO rotation into the speed and direction the implement needs. The gearbox input shaft also has a splined bore, and it must match the shaft's implement-end yoke. A 6-spline implement gearbox paired with a 21-spline shaft yoke simply won't connect. Always confirm both the tractor-end and implement-end spline configurations when ordering.

Individual Spline Yokes and Parts

If only the yoke is worn (spline teeth rounded but shaft tubes and cross-bearings are still good), you can order just the yoke as a replacement part. We stock 6-spline, 21-spline, and metric 8-spline yokes individually. Cross-bearing kits, safety shields, and tube pairs are also available separately from our Korea product catalog.

Why This Spline Shaft

• ✶ CNC-machined spline bores held to ISO 500 tolerances for a precision fit with no play
• ✶ Full range: 6-spline, 21-spline, 20-spline, and metric 8-spline yokes in stock
• ✶ Forged 40Cr yokes with aligned grain structure for long fatigue life
• ✶ Compatible with Kubota, Yanmar, Iseki, John Deere, Massey Ferguson, and other tractor brands
• ✶ CE, ISO 9001, TS/16949 certified production with batch-traceable material records
• ✶ Korean-speaking technical team confirms spline compatibility before each order ships
• ✶ Pricing 30 to 45 percent below OEM for equivalent 6 and 21 spline shaft specifications

Frequently Asked Questions

How do I know if I need a 6-spline or 21-spline Tractor PTO Spline Shaft?

Count the teeth on your tractor PTO stub. Six large teeth = 6-spline (usually 540 RPM). Twenty-one fine teeth = 21-spline (usually 1000 RPM). If your tractor has a dual-speed PTO with a selector, you may have a switchable stub or separate stubs for each speed.

Can I use a 6-spline shaft on a 1000 RPM PTO?

Only if your tractor has a 6-spline 1000 RPM stub, which some older models do (1-3/4" diameter, 6 splines). Don't try to run a 6-spline yoke on a 21-spline stub. The teeth won't engage and the shaft will spin freely without transmitting torque.

My Kubota has a metric spline. Do you stock that configuration?

Yes. We carry 8-spline yokes in 38x32mm, 42x36mm, and 48x42mm for Kubota, Yanmar, and Iseki tractors. These are in stock at our Korea warehouse alongside all inch-series options.

What causes spline teeth to round off prematurely on an agricultural PTO shaft?

Three main causes: operating with a loose-fitting yoke that allows rocking between teeth, failing to apply anti-seize compound which leads to corrosion and fretting wear, and under-specifying the shaft series relative to the tractor HP which overloads the spline interface.

Can I replace just the spline yoke without buying a complete new shaft?

Yes. Individual yokes are available in all spline configurations. If the tubes and cross-bearings are still in good condition, replacing only the worn yoke is the cost-effective repair. Our team can match the yoke to your existing shaft series.

What anti-seize compound do you recommend for the Tractor PTO Spline Shaft?

Any copper-based or nickel-based anti-seize paste rated for steel-on-steel contact. Apply a thin coat to the PTO stub splines each time you connect the shaft. It prevents galvanic corrosion and makes disconnection significantly easier after extended use.

Customer Reviews

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Chung Myung-soo, Kubota Tractor Owner, Gyeonggi-do (spring 2025)

"My Kubota L3560 uses the metric 8-spline 38x32mm PTO stub. Finding replacement shafts with that spline locally was always a problem. Ever-Power had the exact metric yoke in stock. The spline fit is tight with zero play, which is exactly what I wanted."

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Im Jae-hee, Farm Equipment Shop, Cheonan (late 2024)

"I stock both 6-spline and 21-spline versions of this shaft. Customers come in with their old shaft and I match the spline count and diameter on the spot. The CNC-machined bores on these yokes are consistent, which means I can rely on the fit without test-fitting every unit."

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Hong Soo-bin, Dairy Farm, Jeju-do (early 2025)

"Needed a 21-spline shaft for our 85 HP tractor driving a TMR mixer at 1000 RPM. The Tractor PTO Spline Shaft in S8 series arrived with the correct spline, correct length, and the friction clutch I specified. No adapter rings, no shimming. Just bolted on and went to work."

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Yang Dong-ho, Rice Machinery Cooperative, Jeollanam-do (mid 2024)

"Our co-op has twelve tractors from four different brands. Getting the spline right on each replacement shaft used to be a headache. Now we just tell Ever-Power the tractor model and they confirm the spline and ship the right shaft. Haven't had a mismatch yet."

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Min Ye-na, Yanmar Dealer Service, Busan (fall 2024)

"Yanmar tractors in the Korean market use a few different spline variations. I was pleasantly surprised that Ever-Power stocks the less common 42x36mm metric 8-spline for the larger Yanmar EF series. Saved me from having to special-order from Japan."

Packing and Shipping