Swing Shaft is the 39th Expert stage in Challenge Mode and World 8-9 in Story Mode.
There is a long rectangular block that tilts left and right. Down the middle of the block lies a row of smaller blocks that are evenly spaced apart. The goal is on a C-shaped platform on the other side of the tilting block; there are 4 single bananas on the C-shaped platform.
There is only one goal, the blue goal. Get close to the tilting block and get on the side that is lower when the block is about to tilt in the other direction. As you roll forward, balance yourself, and smoothly slide in between two of the smaller blocks to get to the other side of the block as it tilts the other way. Getting off the block and onto the C-shaped platform is very tricky because you have to roll on a narrow path perpendicular to the tilting block. When you are ready, head onto the narrow path in the direction of the next tilt so that the block lifts you high enough to let you roll onto the path. The goal is on the other side of the C.