I know how it works, one range allows the car to take off in 2nd gear and the other allows you to use all three gears. What is the purpose? It seems that you have to pull back to low if you wnat to keep it in gear when drag racing.
Thanks
In the beginning, the C4 was a dual-range automatic transmission, meaning you could drive it in two individual ranges depending on driving conditions. For most with '65-'66 Mustangs, that means driving on the little dot or the big dot on the transmission selector-big dot for normal driving and small dot for Second gear only in ice and snow. It didn't take Ford long to figure out this idea didn't work well because not enough people understood it. Some chose to drive on the small dot in error, never leaving Second gear and burning up the transmission.
Beginning in 1967, Ford made the C4 more like other automatics of the period, with a more traditional P-R-N-D-2-1 shifter pattern, ditching the dual-range idea altogether. This made the C4 more user-friendly. From then, the C4 experienced a lot of refinements that made it durable, and it remains the simplest, most reliable Ford automatic ever. Many late-model Mustang racers have come to know the C4 as a terrific automatic transmission for racing, even choosing it over GM's two-speed Power Glide automatic for some racing applications.
The first paragraph I posted deals with 65/66 C4s, the second deals with 67 and up. If you have a 73 stang with matching C4 then read the second paragraph...