The first two M36 prototypes, designated 90 mm Gun Motor Carriage T71 were completed in September 1943.
It was decided that production vehicles would use the chassis of the M10A1 tank destroyer, as significant numbers of M10A1s were available, and it was determined that the M10A1 had superior automotive characteristics. After testing, an initial order for 300 vehicles was issued. The T71 was designated upon standardization on 1 June 1944 as the 90 mm Gun Motor Carriage M36.