# 1880 Dunbier H3074 Mackay Hydraulic Union Connection (O/R Coupling and Caliper) | Marine Trailer Part

🔧 Product Description

  

Dunbier Hydraulic Union Connection for Override Coupling and Caliper - Part Number: 1880

  

A brake-system hydraulic fitting used to adapts the brake line to the compatible override coupling or caliper port. The fitting is dimensioned for the Dunbier/Mackay trailer brake-line system and must be matched by thread, flare type and tube size.

  

⚙️ Key Features

  

• Trailer hydraulic brake fitting

• Compatible with the Dunbier/Mackay brake-line family

• Corrosion-resistant brass, plated steel or copper construction as applicable

• Allows service or custom routing of trailer brake plumbing

• Designed for pressure-tight brake-fluid connections

  

📏 Specifications

  

• Mackay reference: H3074

• Brake line size and flare type must match the installed system

• Thread must start by hand without force

• Use sealing gasket only where the fitting is designed for one

  

🔄 Cross Reference & Related Parts

  

• Dunbier: 1880

• Mackay: H3074

• Related braided brake lines: Dunbier 1893-1901

• Related rigid Bundy tubes: Dunbier 1890-1900

  

🚤 Trailer Compatibility & Application

  

• Suits compatible Dunbier hydraulic disc-brake systems

• Not interchangeable with metric, bubble-flare or automotive fittings unless thread and seat are identical

• Inspect mating ports before installation

  

🔌 Function

  

Provides a sealed hydraulic connection that adapts the brake line to the compatible override coupling or caliper port.

  

Common signs of wear or replacement:

  

• Brake fluid weeps at the fitting

• Threads or flare seat are damaged

• Fitting is cracked, rounded or heavily corroded

• Line cannot be tightened without misalignment

• Air repeatedly enters the system at the joint

  

🛠️ Installation & Safety

  

• Use proper flare-nut spanners

• Do not use thread tape on flare-seal fittings

• Replace copper gaskets after disturbance where specified

• Support lines to prevent vibration fatigue

• Pressure-test and bleed the system after service

  

📦 Condition

  

• Genuine Dunbier Marine Products trailer component

• Brand new

• Supplied as one hydraulic brake-line fitting

• Supplied in original or equivalent packaging

## Details

- **Price:** 6.3 AUD
- **Vendor:** Dunbier
- **Tags:** Dunbier Boat Trailers | Marine Trailer Parts & Accessories

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 6.30 AUD | In stock |

## Images

- 1880 Dunbier H3074 Mackay Hydraulic Union Connection (O/R Coupling and Caliper) | Marine Trailer Part
- 1880 Dunbier H3074 Mackay Hydraulic Union Connection (O/R Coupling and Caliper) | Marine Trailer Part
- 1880 Dunbier H3074 Mackay Hydraulic Union Connection (O/R Coupling and Caliper) | Marine Trailer Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/1880-dunbier-hyd-union-connection-o-r-coupling-caliper-mackay-h3074)
> Updated: 2026-08-03