Velvet Drive 5-Inch Output Coupling A4547HA | 10-Tooth Coarse Spline

Velvet Drive 5-Inch Output Coupling A4547HA — 10-Tooth Coarse Spline

Overview

The A4547HA is a marine transmission output coupling for early-style BorgWarner / Velvet Drive transmissions. It mounts to the transmission output shaft via a 10-tooth coarse spline and connects to the vessel’s propeller-shaft coupling flange. The 5-inch flange diameter and 4.25-inch bolt-circle are the key dimensional identifiers for this coupling position. A correct-fitting output coupling is critical for maintaining propeller-shaft alignment and preventing driveline vibration and seal wear.

Compatible Applications

• BorgWarner / Velvet Drive 71-series marine transmissions
• BorgWarner / Velvet Drive 72-series marine transmissions
• 72-series direct-drive transmissions
• Early-style Velvet Drive reduction transmissions using the 5-inch coarse-spline coupling configuration

Fitment note: Velvet Drive transmissions were also fitted with 4-inch coarse-spline output couplings in some configurations. Spline count alone does not confirm the correct coupling — verify the flange diameter, bolt-circle, and transmission identification tag before ordering.

Dimensions

• Flange diameter: 5.00 in.
• Spline: 10-tooth coarse spline
• Bolt-circle diameter: approx. 4.25 in.

Kit Contents

• 1 × A4547HA output coupling assembly
• Mounting hardware not included — reuse existing coupling hardware or source separately

Service Interval

Inspect the output coupling at every major drivetrain service or when vibration increases. Replace when inspection shows any of the following:

• Visible spline wear or damage on the internal bore
• Excessive shaft play at the coupling
• Damaged, distorted, or cracked flange faces
• Elongated bolt holes
• Corrosion affecting structural integrity
• Driveline vibration traced to the coupling

Installation Notes

• Inspect the transmission output-shaft splines for wear before fitting the new coupling
• Verify full spline engagement before torquing
• Clean both mating flange faces before assembly
• Check the propeller-shaft coupling face for damage or distortion
• Use the specified coupling hardware at the correct torque
• Perform a proper shaft-to-transmission alignment check after installation
• An improperly aligned coupling will cause vibration, accelerated bearing wear, shaft seal failure, and potential transmission damage

Cross-Reference / Alternate Part Numbers

• A4547HA — SKU as supplied
• BorgWarner / Velvet Drive 4547AY — documented 5-inch, 10-tooth coarse-spline coupling (confirm physical match before substituting)
• ALT23323 — aftermarket reference for the 4547AY configuration

Note on 4547BA: The 4547BA is a related but different Velvet Drive coupling associated with the 10-17 direct-drive transmission. It is not interchangeable with the 5-inch 4547AY / A4547HA configuration — do not substitute without confirming the transmission model and output-shaft spline.

Related Parts

• Borg Warner Output Flange
• BorgWarner Output Flange — 4-Inch Coarse Spline 10-Tooth (related smaller-diameter variant)
• Borg-Warner Output Nut 4775L
• Borg Warner Shift Spool O-Ring — Velvet Drive 71C / 72C | 4804H
• Borg Warner Velvet Drive Oil Pump — 71C / 72C Series | 71C-A60
• Browse all Couplings & Drive Components
• Browse all Transmission Parts & Components

Technical FAQ

Is A4547HA the same as BorgWarner 4547AY?

The A4547HA SKU strongly matches the documented BorgWarner / Velvet Drive 4547AY 5-inch, 10-tooth coarse-spline coupling based on dimensional and application data. However, A4547HA has not been confirmed in publicly indexed manufacturer catalogs under that exact number. Verify the physical part, packaging, or supplier cross-reference before treating them as identical.

How do I confirm the correct output coupling for my transmission?

Locate the transmission identification tag and record the model number. Measure the existing coupling’s flange diameter and bolt-circle, and count the spline teeth on the output shaft. Confirm all three — diameter, bolt-circle, and spline count — match this coupling before ordering.

What is the difference between the 5-inch and 4-inch coarse-spline couplings?

Both use a 10-tooth coarse spline but have different flange diameters and bolt-circles. The 5-inch version (A4547HA / 4547AY) is used on 71 and 72-series transmissions in certain configurations; the 4-inch version is used in others. Spline count alone does not determine which coupling your transmission requires — flange diameter is a critical identifier.

Can I use 4547BA instead of A4547HA?

No. The 4547BA is associated with the 10-17 direct-drive transmission and is not the same configuration as the 5-inch A4547HA / 4547AY coupling. Do not substitute without confirming your transmission model and output-shaft dimensions.

Do I need to re-align the shaft after replacing the coupling?

Yes. Propeller-shaft alignment should always be verified after any output coupling replacement. Even a small misalignment will cause vibration, accelerated seal and bearing wear, and potential transmission damage over time.

Parts Desk Insights

Best use case: The A4547HA is the correct coupling for Velvet Drive 71 and 72-series installations that use the 5-inch, 10-tooth coarse-spline output configuration. It’s a high-value driveline component — at this price point, customers are typically doing a full drivetrain overhaul or replacing a damaged coupling after a hard impact or prolonged vibration damage. The related Borg Warner Output Flange and output nut are natural add-ons for a complete service.

Common customer questions: The most frequent issue is customers confusing the 5-inch and 4-inch coarse-spline versions — both are 10-tooth, so spline count alone does not resolve the order. Always ask for the transmission model number and the existing coupling’s flange diameter. The second common issue is uncertainty about whether A4547HA equals 4547AY — advise customers to confirm the cross-reference from their supplier invoice or the physical part number before completing the order. Shaft alignment after installation is frequently skipped by DIY customers and should be flagged proactively.