After being dropped, I repaired the damaged shell to my HO Southern Pacific Post War #4464 engine.

I'm at a loss as to how the square drive axles keep from sliding off  the bearing. 

Two of the drive wheels on the engine keep sliding out of the plastic connector that keeps the left and right wheel in proper alignment. The two halves of the  plastic connector make a small barrell spacer that seperates the wheels.  It fits inside the center ring of each wheel.  Does anyone know how to cure this problem?

It runs fine once on the track but when you pick it up two of the wheels will slide out.

Thanks,     Cam