Which Tranny Is This?

Being that "new" (1977!) it may have a lockup converter. TF-6 is industry slang for 904, short for Torqueflite 6, because the A904 was primarily installed in slant six and light duty cars, while the TF-8 (A727) was used primarily in trucks and heavier duty applications with 8cylinder engines, although there is a version of the A727 with a slant six bellhousing, used in some dodge trucks in the early 70's.