What is yours doing? I'm interested in their failure modes. I got a "depot rebuild" air shift and just finished putting it in instead of a sprag, and it's no good. It pops out of gear on deceleration, which pretty much means the gears are worn down.

I removed the top cover to see if the detent spring, plunger and ball were intact and okay, and there was a stack of tiny washers on the plunger shaft, trying to increase spring tension. (But there was nothing wrong with the spring.)
Shiny clean paint and a rebuild tag doesn't necessarily mean anything!
I am planning to get a gasket set and open both up and swap parts between the two to make a good one... replacing anything that doesn't meet wear limits. My old sprag wouldn't engage, but it never popped out of gear. Fortunately the t-case/tranny TM was here on this site. Thanks Guys!
Good luck.
Regards,
Jon