school me on part throttle kickdown valve bodies...

abodyjoe said

so if i put the later PTK stuff on my 70 valve body then i'll be able to part throttle kickdown at any speed? is that what i'm reading?

i have a 75, 77, and 79 (from my express truck) valve bodies laying around that i could use too.. is that limit valve worth having work?

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Essentially, the later part throttle kickdown in the earlier valve body will behave like the earlier A904/Slant Six unit would in that same valve body. Part throttle kickdown will occur up to the same vehicle speed that wide open throttle kickdown could occur, but should not normally occur at any higher speed than that.

The limit valve was added to prevent the 3 to 2 downshift at a higher vehicle speed where a part throttle downshift might not be desirable. Above this speed with the limit valve, only a wide open throttle 3 to 2 downshift is possible up to the dowshift limits determined by other transmission parameters, including governor weights, throttle pressure, line pressure, etc.

For a 2.76:1 axle ratio, if the limit was 35-50 MPH, it would move upward, to possibly 55-65 MPH as an example, or about wherever wide open throttle 3 - 2 downshift last occurs.