AD-21-6A Male Female Adapter 1.375" 21 Inner Spline 1.75" 6 Outer Spline for PTO
Technical Data
The AD-21-6A Male Female Adapter is engineered to bridge different PTO shaft configurations with precision and reliability. Featuring a 1.375" (1 3/8") inner bore with 21 splines and a 1.75" (1 3/4") outer shaft with 6 splines, it ensures smooth power transfer between mismatched driveline components. Built from high-strength steel and treated with a corrosion-resistant finish, this adapter provides long-lasting durability even in harsh agricultural and industrial environments. Its secure, easy-to-install design makes it the perfect choice for adapting PTO systems and extending equipment versatility.
Adapt your PTO system with confidence — the AD-21-6A ensures smooth power transfer between 21-spline and 6-spline shafts with unmatched durability.
Features and Benefits
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Converts 1.375" (21-spline female) to 1.75" (6-spline male) PTO connection
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Heavy-duty steel construction for superior strength
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Corrosion-resistant finish for long service life
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Designed for tractors, farm implements, and industrial equipment
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Ensures smooth and efficient torque transfer
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Quick and secure installation for reliable use
Technical Specifications
| Specification | Value |
|---|---|
| Part Number | AD-21-6A |
| Brand | Aftermarket |
| Part Type | Male-Female PTO Adapter |
| Inner Splines Count | 21 |
| Inner Spline Diameter | 1.375 in (34.9 mm) |
| Outer Splines Count | 6 |
| Outer Spline Diameter | 1.75 in (44.4 mm) |
| Length | 6.81 in (173 mm) |
| Female End | 1.375 in (21 splines) |
| Male End | 1.75 in (6 splines) |
| Material | Steel |
| Warranty | 1 Year |
Vehicle Compatibility
| Equipment Type | Application |
|---|---|
| Tractors | PTO driveline conversion (21-spline to 6-spline) |
| Agricultural Equipment | Farm implements, mowers, balers, harvesters |
| Industrial Equipment | PTO-driven machinery with mismatched shaft sizes |
| General PTO Systems | Adapts between 1 3/8" 21-spline female and 1 3/4" 6-spline male shafts |
What's Included
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1x AD-21-6A Male-Female PTO Adapter (21 inner spline x 6 outer spline)
REVIEWS
Exactly what I needed for my tractor PTO conversion. Fits perfectly and feels very solid. Made connecting my mower a breeze.
John D.
Boise, ID
Great quality adapter. Installed in minutes and has been holding up well under heavy use on my baler. Highly recommend.
Steve M.
Lexington, KY
Specifications
Fitment Data
• Engineered for precision compatibility with high-performance builds.
• Tested under extreme mechanical stress for guaranteed structural integrity.
Use the Riot Vehicle Finder to verify exact sub-model compatibility.
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