Thanks @maxi-model I tried that part and it doesn’t fit. Thank you @Gizzy
Hmm. Yes, the front two drivers use different size connectors. Connectors then might be for the pony truck. Neither are shown as separate part assy's though.
Picture of a still born project using a heavily modded 4-6-0, aka "Annie", chassis. This, like yours, is identifiable by its metal rods and motions. The regular 4-6-0 used plastic parts there. Axle connectors are labled as universal between both 4-6-0 types. But not for our Annies, back to the pony truck then ? Base plate of chassis removable by 3 screws, then everything can be got at. You need to remove the coupling rods, those 3 large hex head screws are holding them on to the wheels, each side. That will the allow you to remove the motions to get at the axles and release them individually.
You might try to find a hard plastic tube, that will have an interference fit to the square axle stubs, that you can use to align and hold in place. You have the other two axles at either end that should take care of any risk of "quartering" issues messing with the motions. Max
