It's not necessarily the axle shafts, as it sounds like they're made to factory Ford specs. However I did think we specified ring grooves further out, or dual groves to combat this issue. But in the end it's the Warn lockouts themselves (and most other aftermarket versions) that causes the problem. Same issue with stock lockouts, when using the GM based disc brake kits. With both the brakes and the Warn products, it's a double-whammy against us.
So in either of those latter cases, even with the stock axles you rarely have room for the small snap ring on the axle. As in almost never. I think I've only heard of one or two that were able to install the ring once things were changed.
Sounds like our axles are specified to be just like stock then. Too bad, as a groove a little further out would have been nice.
As mentioned, at one point I'm pretty sure we even had a manufacturer that gave us two grooves. One inner for the stock Ford brakes and stock Spicer lockouts, and one outer for aftermarket brakes and lockouts.
As far as I know the issue with Warn hubs has been with us for as long as there have been Warn hubs. Or at least since the late '70's when I first ran across the problem.
My guess has always been that they were designed on the GM version of the Dana axles, presuming that they must all the same, and Ford spindles and axles were just a bit different.
Sounds like a good time to bring it back up and ask for grooves further out on the custom axles. If it's something the manufacturer is willing to do without charging too much.
That's the big issue as I see it really. If all of your products can be made in one-size-fits-all, the cost is one level. If you have to make one single change just to fit Fords, the cost on that version is at another level.
But that's just conjecture. I'll ask around and see what, if anything, can be done.
For now though, as the others have said, just leave the small snap-ring off of the axle shaft. Now, if we're talking about the big one on the bearing hub, that's a whole different story!
Paul