Billet Aluminum Oil Trailer Bath Cap 4"-12 Thread with Wrench
Complete oil bath cap service kit with one billet aluminum 21-36 style cap, center plug, O-ring, and billet wrench. Designed for compatible 4"-12 threaded oil bath hub applications where the 21-36 cap style and measurements match.
Key Measurements & Specs
| Specification | Detail |
|---|---|
| Part Number / SKU | 21-36-BILLET-WRENCH-KIT |
| Product Type | Billet aluminum oil bath cap kit |
| Cap Application | 21-36 style oil bath cap applications |
| Thread Specification | 4"-12 thread |
| Material | Billet aluminum cap and billet aluminum wrench |
| Quantity Included | One complete cap-and-wrench service kit |
Fitment / Application
| Category | Details |
|---|---|
| System Type | Trailer oil bath hub and drum applications |
| Primary Fit | Compatible with 21-36 style 4"-12 threaded oil bath cap setups |
| Referenced Drums | 9-44, 9-27, and 9-28 applications where the 21-36 cap style is used |
| Fitment Method | Verify cap number, thread size, thread pitch, sealing surface, plug style, and drum/hub application before ordering |
| Important Note | Application references are fitment guides only. Match your existing cap and hub specifications before installation. |
Top Features
| Feature | Buyer Benefit |
|---|---|
| Billet Aluminum Cap | Durable upgrade-style construction for compatible oil bath hub applications |
| 4"-12 Thread | Matches 21-36 style threaded oil bath cap applications where measurements confirm fit |
| Center Plug & O-Ring Included | Provides the key sealing components commonly serviced with the cap |
| Billet Wrench Included | Helps with cap installation and removal without needing to source the wrench separately |
Overview
The 21-36-BILLET-WRENCH-KIT is a curated oil bath cap service kit for compatible trailer hub and drum applications using a 21-36 style 4"-12 threaded oil bath cap. The kit includes the billet aluminum cap, center plug, O-ring, and a billet wrench for 2.5" hex cap service, making it a practical replacement or service option when the existing cap style and thread specification match.
R&P Service Insight
Oil bath cap fitment is measurement-driven. A cap that looks close may still leak or fail to seat correctly if the thread, sealing surface, or plug style does not match the hub.
- Confirm the cap number: Match the existing cap to the 21-36 application before ordering.
- Check the thread: Verify 4"-12 thread compatibility on the hub or drum assembly.
- Inspect the seal area: Replace damaged plugs and O-rings when servicing oil bath caps to help prevent seepage.
R&P Knowledge Hub
Compatibility: This kit is intended for compatible 21-36 style oil bath cap applications using a 4"-12 thread. Verify before ordering if your hub, drum, or axle setup has been changed from its original configuration.
Referenced Drum Applications: Common application references include 9-44, 9-27, and 9-28 where the 21-36 oil bath cap style is used.
Installation Notes: Clean the hub threads and sealing surface before installation. Do not force the cap if the threads do not start cleanly by hand.
Performance Insight: The cap retains oil bath lubrication inside the hub and helps protect the bearing system. Proper cap fit and sealing are essential for oil retention and long-term hub performance.
Brand & Fitment Note
Selling Brand: R&P Carriages curated billet oil bath cap kit
Application Reference: References to 21-36, 9-44, 9-27, and 9-28 are used for compatibility and application identification only.
What This Means: This listing is for a billet aluminum oil bath cap kit assembled for compatible 21-36 style applications. It should not be treated as a guaranteed OEM-branded item unless separately verified.
Before Ordering: Verify cap number, thread size, thread pitch, sealing surface, center plug style, O-ring fit, and drum/hub application before installation.
R&P Repair Insight
Oil bath caps are often replaced because of damaged threads, leaking plugs, worn O-rings, cracked caps, or cap damage from removal. This kit is built to cover the cap and common sealing pieces while also including the matching billet wrench for service.
- Leak check: If oil is present around the cap face, inspect the center plug and O-ring before reusing old sealing parts.
- Thread check: Damaged or crossed threads can prevent proper seating and may cause leaks even with a new cap.
- Tooling check: Use the correct wrench profile for the cap to reduce damage during installation or removal.
Features
Billet Aluminum Construction
Durable billet aluminum cap designed for compatible oil bath hub applications using the 21-36 style cap format.
4"-12 Thread Application
Built for 4"-12 threaded hub cap applications where the existing cap and hub measurements confirm fitment.
Service Components Included
Includes the center plug and O-ring, giving buyers the common sealing pieces needed during cap replacement.
Billet Wrench Included
Comes with a billet aluminum wrench for 2.5" hex caps, helping simplify future installation and removal.
Included Components
| Part Number | Quantity | Item |
|---|---|---|
| 21-36 | 1 | Billet aluminum oil bath cap, 4"-12 thread application |
| 046-032-00 | 1 | Center plug |
| 010-050-00 | 1 | O-ring |
| Billet-Wrench-2.5 | 1 | Billet aluminum wrench for 2.5" hex caps |
