Toe angle shifts in 4x4

[derbyhunk]

I've been digging into an odd issue with my Yanmar 424 in 4x4. When I roll the tractor backwards, the front toe angle shifts, and then when I move it forwards, it changes again. It's consistent every time, so it's not just my eyes playing tricks.
From what I can tell, this points to something moving in the front axle or steering system, what can it be

 

[crankshaftcoffeeclub25]

Typically, you'll find that the issue lies in the front axle pivot or some worn-out tie rod ends. It's a good idea to take a look at the bushings, kingpins, and steering linkage as well.