It was mentioned that Marv Ripes of A-1 transmissions created the 3-speed auto for the comp eliminator guys. There is actually more to this story.
Being a performance class, comp eliminator has had some serious efforts over the years and torque converter development was a major contributor to increased performance. Several different PG ratios were used to tailor the optimum set-ups. Marv Ripes, being a cerebral thinker, thought that many of the cars, particularly some of the small motor/heavier cars, could use an extra gear. Problem was, a turbo 350 or 400 was so heavy internally that what ever gains there were from better gearing was lost through the heavier intertia of the internal weight. Marv was friends with Mike Smith, a racer himself plus a transmission builder. Smith said that the Chrysler 904 3-speed TF was a very efficient and LIGHT transmission. It was first made in 1960 for the new slant six cylinder compact cars. By the mid-60s this trans had been made available for small blocks (Chrysler never had a 904 for a big block) and by the early 70s Chrysler supplied American motors with both 727 and 904 torqflites.
The AM trans used a passenger side starter, and the bellhousing diameter was more compact then the Chrysler models, making this easier for use on a Chevy. Mike Smith offered to make A-1 an AM cased 904 with mounting adapter for the Chevrolet bellhousing pattern. The trans worked well beyond expectations and Marv Ripes got an exclusive sales agreement from Mike Smith, who named his business Pro-Trans. In NHRA comp classes, this trans is called the "A-1 3-speed", though every one has been built by Pro-Trans.
Pro-Trans does a lot of trans building for NHRA Stock and Super Stock racers. Virtually all Mopar auto S/SS racers use the Pro-Trans 904/727. a special conversion of the 904 internals placed into a 727 case, thus getting around the NHRA's ban on transmission adapters, which isn't a problem with Small Block and Big block Chevys which have a shared bolt-pattern, whereas Chryslers use different patterns for the small and big blocks.
Pro-Trans has been building lots of Ford C4 and C6 transmissions with the 904 internals. The strength of these 904 derived transmissions is remarkable, as exemplified by all of the SS/AH '68 Cuda/Dart Hemi shootout auto equipped cars using the 904 in a 727 case; remember, this is a slant six auto.
-Andy Carlson
Ojai CA