What Dexter Fortress Threaded Aluminum Oil Cap do I Need for My 10k AL-KO Axles?

Updated 10/28/2025 | Published 03/16/2025

Question:

I have a 2005 Top Hat Industries gooseneck with 10k AL-KO axles. I am looking for a set of new oil caps for the axles. Do the Dexter Fortress Threaded Aluminum Oil Cap for 10K to 16K Axles fit my axles? I have had trouble finding a set that will seal due to the tappered inside of the hub.

asked by: Ethen K

Expert Reply:

Hello Ethen,

I am happy to make sure we get you the right cap. The Dexter Fortress Threaded Aluminum Oil Cap # DX59CR is made specifically for Dexter 10K to 16K axles, and while it might thread into your 2005 Top Hat's 10K AL-KO axles, it likely won’t seal properly. The issue comes down to the inside of the hub, Dexter hubs typically have a straight bore where the oil cap seals, but many AL-KO hubs from that era have a tapered seating surface inside. That taper can prevent the o-ring on the Dexter cap from making full contact, which means you could end up with leaks even if the cap seems to fit.

So while it might technically screw in, it’s not a guaranteed match due to that taper. The better route would be to look for an oil cap designed specifically for AL-KO 10K axles. Can you please respond back to the email with a picture of your axle tag so I can reach out to our friends at Dexter so we can find you the right fit?

expert reply by: Kate F

Example of AL-KO Axle Tag
(click to enlarge)

Kate F.

10/27/2025

Hey Ethen, were you able to track down an oil cap that seals properly on your AL-KO 10K axles? Knowing what ended up fitting could help others with the same tapered hub issue.