The bad gear was all celeron (or phenolic) including the teeth... which was what didn't last. The 'new' gear has an aluminum rim & teeth on a 'celeron' hub. Franklin Service Bulletin # 17 Feb. 13, 1942 addressed this and said replace them at overhaul (500hrs.)
The rate of wear (failure?) apparently was higher then they thought and with S.B. #21 of Dec. 7, 1942 (1 yr. after Pearl Harbor) they said pull any accessory and replace immediately if not previously done.
If you have a 4AC-199 S/N 200533 or higher they came with the new gear. If you have a 4AC-176 S/N 125270 or higher - same thing.
Old gear P/N not given - new gear P/N 10725 (cost at that time was $6.00 !! )