• Drill a hole in the center of both sides of each wheel. Holes should be just large enough for wire to fit through snugly.
• Cut
  a piece of wire 3¾ inches long for the rear axle and 3¼ inches long for
  the front axle. Each axle should be as straight as possible. Use pliers
  to straighten wire if it is curved or bent.
• Drill holes in washers, then cut washers out.
• Pass
  axles through axle holes at front and rear ends of truck. Slip washers
  and then wheels onto axles. Position so that wheels are close to the
  truck but not so close that they rub against the sides. Glue each wheel
  in place with a drop of super glue applied to the axle where it exits
  the wheel.
• When glue is completely dry, check operation of the wheels. If wheels wobble, apply gentle pressure to straighten axle wire.

If you want your truck to be immobile, simply glue axles to chassis with super glue.