Abstract: Apparatus for adjustably mounting bogie wheels on a frame member or slide rail of an endless track assembly for snowmobiles. The apparatus includes coaxial pairs of bogie wheels on each rail, one wheel mounted on either side of said rail, each of such pairs being independent of all other wheels and rails in the assembly. The bogie wheels are adjustable to convert the assembly from one in which the track slides along the rail to one in which the track is spaced below the rail by said bogie wheels. The length of the track engaging the supporting snow surface is also adjustable. Various means for adjusting the bogie wheels with respect to the rail are provided including a bogie wheel axle mounting cylinder having a plurality of ridges about its circumference received in a mounting block on the track rail. The cylinder is inserted in any of a plurality of positions in the block to position the axle, the ridges holding the cylinder and axle as desired.