How do Warn hubs work?

[redlump]

Hi,

Eighteen months ago, a Kia dealership replaced the broken 4wd front vacuum hubs on my 2000. They just quit again.
(I ran brand new vacuum lines to both hubs yesterday, verified a vacuum was present, and still no lock.)

Anyway, I have just ordered the Warn Automechanical (61918) locking hubs.

Can anyone explain how these work? With no input from a vacuum line or an electrical signal, what prompts them to lock automatically?
(I have found installation instructions online, but nothing to explain how they work.)

Thanks!

Rob

[mgbgt1972]

Should have ordered the manual lockers, they hold up much better. If your vaccum hoses have gone, you may want to change the front bearings when you change the hubs!

The warn auto lockers use a cam to engage, and in canada the kia vaccum units were replaced in a recall with re-badged warns cam units.

[redlump]

Yeah...Cam.
Presumably once the drive shafts have power and start spinning, the cam locks the hubs? That's the part I don't get.

And is it necessary to back up a few feet to disengage them?

Installation turned out to be more than a 10 minute job.
On both wheels the old hub was rusted onto the wheel, and when I got over that, I had to drill out the screws holding the set plate on.
Shouldn't have been surprised. Every single fitting on that vehicle has already rusted to failure, or failure is imminent.