Method is provided for after market conversion of a 4.times.4 vehicle produced by a manufacturer into a high mobility vehicle having increased maneuverability and on-road and/or off-road capability, relative to the 4.times.4 vehicle. The 4.times.4 vehicle has a chassis with a frame, front axle and rear axle, said chassis having a standard wheelbase. The method includes dismounting at least one of the front axle or rear axle from the frame; shortening said frame; and mounting the dismounted axle to the shortened frame so as to obtain a shortened chassis having a shortened wheelbase which is shorter than any standard wheelbase of the line of models produced by the manufacturer.