Nit: There's no such thing as a Grumman TBM and there never was. Grumman Avengers were TBFs, Eastern Aircraft, a division of GM, made TBMs.
Quote from the CAF website:
"
restored TBM/TBF Avenger"
"The prototype TBF was designed in 1940 by Bill Schwendler of Grumman Aircraft. It first flew on August 1, 1941. The TBF was primarily designed to replace the obsolete Douglas TBD
Devastator. The
Avenger name was adopted subsequent to the attack at Pearl Harbor. Although the
Avenger had an inauspicious start at the Battle of Midway, be sure to read its final score below!
Once accepted by the Navy, Grumman built 2,291 TBFs before General Motors, Eastern Aircraft Division, began building them under license from Grumman. The US Navy nomenclature designated these identical aircraft as TB
Ms with GM building 7,546 for a type total of 9,837. (TBF = Grumman-built, and TBM = GM built)
Early models of both the TBF and TBM had Wright "Twin Cyclone" R-2600-8 engines developing only 1700 hp. Later production saw increases in power up to 1900 hp with the R-2600-20 engine. This engine was also used on the Boeing 314
Clipper flying boat, B-25
Mitchell, and some models of the A-20
Havoc. TBM-3s, with nearly 4,000 being built, had the more powerful engines. This required more cooling, the oil cooler was moved to the lower engine cowl lip and four more cowl flaps were added to each side. These changes and the removal of the 30 caliber ventral "stinger" gun are the primary visual differences between early and later model
Avengers."
