In 1938 the GAZ AA was substituted with more advanced lorry GAZ MM. The radical departure from the predecessor became its engine of 50 hp capacity moreover the suspension was strengthened and the steering and the propeller shaft were changed. The loading capacity remained at the previous level — 1.5 ton. The same year the ambulance was worked out on the base of the GAZ MM, which got the index mark GAZ 55. The automobile received a closed wagon-body inside of which four stretcher cases and two sitting cases on the throw-back seats could be located. Altogether 9,130 pieces of the GAZ 55 were made from 1938 till 1946. From autumn 1942 till 1945 a simplified automobile version was produced, that got angular front fenders and the rear wings also had a simplified construction.

Curb weight, kg – 2,370
Length, mm – 5,425
Width, mm – 2,040
Height, mm – 2,340
Cylinder number - 4
Displacement, l - 3.28
Power, hp - 50
Speed, km/h - 70