OIL CAP KIT, 1 AXLE DEXTER 6K, 8K (9K PRIOR TO 10/89)

What it is

The oil cap kit is a sealed cap assembly that fits onto the end of the wheel hub. It typically includes:

• A transparent or metal cap
• A rubber plug (fill plug)
• Seals or O-rings

Main function

Its job is to contain and protect the lubricating oil inside the hub. That oil keeps the wheel bearings properly lubricated.

What it actually does

• Seals the hub → prevents oil from leaking out
• Keeps contaminants out → blocks dirt, dust, and water from entering
• Allows oil inspection → many caps are clear so you can visually check oil level and condition without disassembly
• Provides access for maintenance → the rubber plug allows you to add or change oil easily

Why it matters

On Dexter 6K–8K axles (commonly used on medium-duty trailers), proper lubrication is critical. Without a functioning oil cap:

• Bearings can lose lubrication
• Contaminants can enter and cause premature wear or failure
• Overheating and hub damage can occur