Abstract: A vibration isolation fifth wheel suspension system comprises a fifth wheel support plate mounted between the spaced parallel frame members of a truck tractor on a pivotal axis located near the forward end of the tractor. The plate is located to rest on the upper surface of the frame members and its free end is mounted on a pressurized air suspension supported by a cross member extending between the tractor frame members. Two pairs of first and second cooperating wear plates are used to minimize lateral shift and roll of the support plate. The first plate of each pair is attached to and depends downwardly from the under surface of the support plate in sliding relationship with the second plates of each pair which are fixed to the cross frame member.