One of the most common questions we get from customers is:
Q: “Hello, does the Carter aluminum oil cap fit or replace the oil bath 2188 plastic existing cap on my 2021 10K Dexter trailer axle (part #21-88)?”
A: Yes — the Carter 10K forged aluminum oil cap (part number KC21-302) threads directly into place as a perfect replacement for the Dexter 21-88 plastic oil cap.
Why Upgrade From Dexter’s 21-88 Plastic Cap?
Dexter’s plastic oil bath cap (21-88) works fine when new, but over time heat, pressure, and vibration cause the plastic to crack, warp, or leak. That’s when problems start.
The Carter forged aluminum oil cap is built to handle real-world hauling:
- Forged aluminum construction – stronger than plastic and far more resistant to heat cycles and road abuse.
- Screw-in design – threads right into the hub just like the original Dexter 21-88 plastic cap.
- Better sealing – includes the O-ring and plug for a tight, leak-free fit.
- Cross-brand compatibility – fully interchangeable with Dexter Fortress aluminum caps and Valcrum caps.
The Correct Replacement Part Number
If you’re replacing a Dexter 21-88 plastic cap, the part you need is:
Carter KC21-302 Forged Aluminum Oil Cap
Designed for:
- Dexter 9K-10K trailer axles
- Carter 10K trailer axles
- Direct replacement for Dexter Fortress and Valcrum aluminum screw-in caps
Click here to order the Carter KC21-302 Aluminum Oil Hub Cap
Why Carter Oil Caps?
At Trailer Parts Unlimited, we recommend Carter because you get the same fit and interchangeability as Dexter or Valcrum without paying the inflated prices. These forged aluminum caps protect your hubs better, last longer, and won’t crack like plastic.
Final Takeaway
If you’ve got a Dexter 10K axle with a 21-88 plastic screw-in oil cap, upgrading to the Carter KC21-302 forged aluminum oil cap is the best solution. It threads in easily, seals tight, and keeps your hubs protected from leaks and damage.
Available for shipping or in-store pickup at:
Trailer Parts Unlimited
631 TX 75 N, Huntsville, TX 77320 (Exit 118 off I-45, next to Pilot and Chicken Express)
Call us at 844-898-8687 or shop online anytime at TrailerPartsUnlimited.com.
