Abstract: A four wheeled undercarriage is mounted to a snowmobile body having a tunnel from which the endless track drive assembly has been removed. The ski-mounting brackets of the snowmobile support the front end of the snowmobile body on a front axle bolster and two steerable wheels. Steering is accomplished through one of these brackets. The rear end of the snowmobile body is supported by two suspension spring assemblies on a triangular rear wheel support frame and two rear wheels. A transversely extending undercarriage positioning bar installed in a forward portion of the snowmobile tunnel positions the forward end of the triangular support frame and adjustably positions the attitude of the front axle bolster to control the camber of the steerable wheels. A stabilizer bar between the rear support frame and the snowmobile body allows vertical movement but restricts lateral movement of the snowmobile body with respect to the rear wheels.