Note that with the black clip not there, the silver truck sides can separate.
Be careful to separate the truck sides enough for the wheelset axles to come
out, but not too much to cause the other axles to come out.

Separate the truck sides enough so the traction-tire wheelset's axle can come out
of the holes on both silver truck sides.

Then, with a small screwdriver tip, CAREFULLY lever out and remove the traction-tire wheelset.
I am showing the removed axle with my tweezers, but I carefully used a small screwdriver tip
to lever out and pop out the axleset.

The axle is a press-fit into the plastic. Be careful and it will pop out.