This is the flywheel ring gear. It has 139 teeth. Inside diameter=13 inches. Outside diameter=14 inches. (Not for Powerglide equipped cars). 139 tooth ring gear must be used w... For 1937 1938 1939 1940 1941 1942 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 Chevrolet Cars and Trucks