X4(FOUR) 3.5" Oil Bath Cap Trailer Axle Dexter 9K 10K 8-415 430 After 2009
Four complete oil bath cap service assemblies with matching O-rings and rubber center plugs for compatible 3.5" trailer oil bath hub applications.
Overview
This R&P Carriages service kit is a four-pack oil bath cap kit built around the 21-88 style cap assembly. Each service set includes one oil cap, one matching O-ring, and one rubber center plug. The kit is intended for servicing compatible 3.5" oil bath trailer hub systems where the existing cap, plug, or seal has become worn, cracked, contaminated, or started leaking.
R&P Service Insight
Oil bath hub caps should be treated as sealing components, not just covers. If the cap or rubber plug is leaking, the bearing cavity can lose oil and take in dirt or moisture.
- Replace as a Set: Cap, O-ring, and plug should be inspected together when oil leakage is present.
- Check the Hub: Verify that the hub threads and sealing surface are clean and undamaged before installation.
- Confirm Size: Match your original 21-88 cap style and 3.5" oil bath hub application before ordering.
R&P Knowledge Hub
Compatibility: Commonly used with 21-88 / 021-088-00 style oil bath cap applications for compatible 3.5" trailer hub systems.
Axle Reference: Often associated with many Dexter-style 9K, 10K general duty, and #13G axle applications manufactured after July 2009. Always verify your exact hub and axle setup.
Installation Notes: Clean the cap threads and hub sealing surface. Make sure the O-ring seats correctly and the rubber plug is fully seated after oil inspection or filling.
Performance Insight: A leaking oil bath cap can lead to oil loss, hub contamination, bearing wear, overheating, and premature service failure.
Brand & Fitment Note
Selling Brand: R&P Carriages service kit using 21-88 style replacement oil cap components.
Application Reference: 3.5" oil bath hubs using 21-88 style threaded oil caps with 010-163-00 O-rings and 046-032-00 rubber center plugs.
What This Means: This listing includes four oil caps, four O-rings, and four rubber plugs — enough to service four compatible oil bath cap assemblies.
Before Ordering: Compare your original cap number, outside diameter, thread style, hub opening, O-ring, and plug style. Trailer axle and hub configurations can vary.
R&P Repair Insight
If oil is collecting around the hub face, cap threads, or rubber center plug, the cap assembly should be inspected immediately. In many cases, the cap itself may be reusable only if the threads and sealing surfaces are clean and undamaged. When in doubt, replacing the cap, O-ring, and plug together is the cleaner service approach.
- Leak Check: Look for oil residue around the cap shoulder, plug opening, and hub face.
- Seal Check: Replace flattened, brittle, swollen, cut, or missing O-rings.
- Plug Check: Replace rubber plugs that are loose, cracked, hardened, or no longer sealing tightly.
Features
Four Complete Service Sets
Includes four caps, four O-rings, and four center plugs for servicing four compatible oil bath cap assemblies.
21-88 Style Oil Cap
Designed around the 21-88 / 021-088-00 oil bath cap style used on compatible trailer hubs.
Includes Sealing Components
Each cap includes the required O-ring and rubber plug components for a complete cap service assembly.
Oil Bath Hub Maintenance
Useful for replacing cracked, leaking, worn, missing, or contaminated oil cap components during trailer hub service.
Specifications
| Specification | Detail |
|---|---|
| Primary Cap Number | 21-88 / 021-088-00 style |
| Listing SKU | 21-88-KIT-LOTOF4 |
| Brand / Supplier | R&P Carriages service kit |
| Product Type | Oil bath cap kit |
| Quantity Included | X4 complete cap assemblies |
| Application | Compatible 3.5" oil bath hub systems |
| Cap Style | Threaded / screw-in oil bath cap |
| Included Seal | 010-163-00 / 10-163 style O-ring |
| Included Plug | 046-032-00 / 46-32 style rubber center plug |
Fitment / Application
| Category | Details |
|---|---|
| Vehicle / System | Trailer oil bath hub systems |
| Primary Fit | 3.5" oil bath hubs using 21-88 style caps |
| Common Uses | Many Dexter-style 9K, 10K GD, and #13G post-July 2009 axle applications |
| Notes | Verify cap number, hub size, thread style, plug, O-ring, and axle/hub compatibility before ordering. |
Included Components
| Quantity | Item |
|---|---|
| 4 | 21-88 / 021-088-00 style oil bath caps |
| 4 | 010-163-00 / 10-163 style O-rings |
| 4 | 046-032-00 / 46-32 style rubber center plugs |
| Not Included | Hub, drum, bearings, oil, tools, and additional hardware are not included unless shown or stated otherwise. |
