PROBLEM TO BE SOLVED: To provide a variable gauge truck for railrood vehicles that can be made compact at its entire part around an axle and that can reduce a backlash between parts which slide as a track changes.
SOLUTION: An axle box 19 is disposed beneath a side sill 15 via an axle spring 17. The axle box 19 comprises an outer box 20 and an inner box 24. A thrust bearing box 21 is horizontally slidably fitted into the axle box 19. A variable positioning mechanism is provided between the axle box 19 and the thrust bearing box 21. The mechanism comprises a recess 20a formed in the inner surface of the outer box 20 and two locking projections 24a, 24b formed on the outer surface of the thrust bearing box 21. The recess 20a and the locking projections 24a, 24b can be fitted together in a tongue-and-groove fashion, and the variable position of a wheel 41 is performed (for varying the gauge) in accordance with the way they are fitted together.