Two - Billet Aluminum Trailer Oil Bath Caps 4"-12 Thread with Wrench
Two-cap billet aluminum oil bath cap kit for compatible 4"-12 threaded hub cap applications. Includes matching center plugs, O-rings, and a billet wrench for installation and removal.
Key Measurements & Specs
| Specification | Detail |
|---|---|
| Part Number / SKU | 21-36-BILLET-WRENCH-KITX2 |
| Selling Brand | R&P Carriages curated service kit |
| Product Type | Billet aluminum oil bath cap kit |
| Thread Specification | 4"-12 threaded oil cap application |
| Material | Billet aluminum cap construction |
| Quantity Included | 2 oil bath caps, 2 center plugs, 2 O-rings, and 1 billet wrench |
Fitment / Application
| Category | Details |
|---|---|
| System | Trailer oil bath hub cap applications |
| Primary Fit | 21-36 style 4"-12 threaded oil cap applications |
| Compatible Drum References | 9-44, 9-27, and 9-28 where the original cap thread and sealing setup match |
| Fitment Method | Verify existing cap number, thread size, cap opening, O-ring style, and plug style before ordering |
| Important Note | Will not fit hubs using a different oil cap diameter, thread pitch, plug style, or sealing arrangement |
Top Features
| Feature | Buyer Benefit |
|---|---|
| Billet Aluminum Caps | Durable metal cap construction for compatible oil bath hub service |
| 4"-12 Thread Fit | Matches 21-36 style threaded oil cap applications when measurements confirm fit |
| Sealing Components Included | Includes center plugs and O-rings needed for the listed cap setup |
| Billet Wrench Included | Provides a dedicated tool for cap installation and removal |
Overview
This R&P Carriages billet oil bath cap kit is built for compatible 21-36 style 4"-12 threaded hub cap applications. The kit includes two billet aluminum oil bath caps, two center plugs, two O-rings, and one billet wrench, making it a practical service set when replacing a pair of oil bath caps on matching trailer hubs.
R&P Service Insight
Oil bath caps are small parts, but they are critical to keeping lubricant inside the hub and contamination out of the bearing cavity. Confirm the cap thread and sealing style before installation.
- Thread Match: Verify the hub uses a 4"-12 threaded oil cap before ordering.
- Seal Surface: Inspect the hub face and O-ring contact area for burrs, corrosion, or old gasket material.
- Plug Style: Match the center plug style to the cap opening before filling or returning the trailer to service.
R&P Knowledge Hub
Compatibility: This kit is intended for 21-36 style 4"-12 threaded oil bath cap applications. Drum references 9-44, 9-27, and 9-28 are application references only and should be verified against the actual hub and cap dimensions.
Trailer / System Fit: Designed for compatible trailer oil bath hubs where a threaded cap, O-ring, and center plug are used to retain hub oil.
Installation Notes: Clean the cap threads, inspect the O-ring seat, lubricate the O-ring as appropriate, and thread the cap carefully to avoid cross-threading.
Performance Insight: A properly sealed oil bath cap helps maintain hub lubrication and protects the bearing cavity from leaks, water intrusion, and road contamination.
Brand & Fitment Note
Selling Brand: R&P Carriages curated billet service kit.
Application Reference: 21-36, 9-44, 9-27, and 9-28 are used as compatibility and application references only.
What This Means: This listing is for an R&P Carriages billet oil bath cap kit, not a guaranteed OEM-branded item unless specifically stated on the product packaging or invoice.
Before Ordering: Verify the existing cap number, thread size, hub opening, plug style, O-ring style, and drum or hub application before installation.
R&P Repair Insight
When servicing oil bath hubs, cap fitment should be confirmed before filling the hub with oil. A mismatched cap can leak immediately or fail to seat correctly even when the thread appears close.
- Check the Thread: Confirm 4"-12 thread before replacing the cap.
- Check the O-Ring: Replace damaged, flattened, cut, or swollen O-rings during cap service.
- Check the Cap Body: Do not reuse a cap or sealing component if the threads, plug bore, or sealing surfaces are damaged.
Features
Pair of Billet Oil Bath Caps
Includes two billet aluminum oil bath caps for servicing both matching hub cap positions on compatible trailer applications.
4"-12 Thread Specification
Designed for 21-36 style oil cap applications using a 4"-12 threaded fitment.
Center Plugs and O-Rings Included
Comes with two 046-032-00 center plugs and two 010-050-00 O-rings for the listed cap setup.
Installation Wrench Included
Includes one Billet-Wrench-2.5 tool for installation and removal of compatible billet cap hex profiles.
Included Components
| Part Number | Quantity | Description |
|---|---|---|
| 21-36 | 2 | Billet aluminum oil bath cap for 4"-12 threaded applications |
| 046-032-00 | 2 | Center plug |
| 010-050-00 | 2 | O-ring |
| Billet-Wrench-2.5 | 1 | Billet aluminum wrench for compatible 2.5" hex cap service |
