ok so i'd like to set the darts 904 for part throttle kickdown.. the trans is fresh (about 7500 miles on it) and in the car so i'm only looking to swap or modify the existing valve body...
trans in it is a 70 so i assume the kit from A&A won't fit because it says 66-69 transmissions.. i may call them monday and question them about it.. i do have a 69 trans here that i could rob the valve body from and use the A&A kit, but then i have to do all the mods to that valve body that mine already has done.
was just out and looking at the valve bodies i have laying around and i think three are part throttle valve bodies.. i'll picture them below. if this is the case, can just take that spacer thing out and put it on my existing valve body? do i have to do anything else to the trans?
if i can just swap that part throttle kickdown stuff over to my trans will it work properly being the valve body had a kit in it and the trans line pressure has been raised?
View attachment 1716471174
The part throttle kickdown assembly from the 1971 and later valve body pictured can be added to the 1970 transmission valve body. Note that one screw on the separator plate to transfer plate must be changed to a low profile thin head screw.
I have not seen the A&A part throttle kickdown unit, but it appears to be a version of the Slant Six/A904 unit, which can be used in 1967 - 1970 valve bodies.
For more general information on both part throttle kickdown units and some detail about the affected screw with the 1971 and later unit, refer to the following:
Part Throttle Kickdown for Pre-1971 Torqueflite Transmissions
By Gary Lewallen, aka. Vaanth
25 October, 2025
Introduction
Part throttle kickdown allows the transmission to downshift without requiring full throttle opening but was not incorporated into A727 Torqueflite transmissions and V-8 A904 Torqueflite transmissions prior to 1971. Part throttle kickdown was introduced in limited release in 1966 (Ref. TSB D67-21-1), and for the 1967 model year, for the A904 transmission with the Slant Six engine.
Part throttle kickdown can be added to 1967 - 1970 transmissions by replacing the valve body with a 1971 or later unit, with some considerations, or by adding the part throttle kickdown components to the earlier valve body. Part throttle kickdown can be added to 1962 - 1966 transmissions with additional modifications.
In 1971, the A727 transmission was revised in several areas, and part throttle kickdown was introduced in the A727 and V-8 A904 transmissions, depending on application. The Slant Six with A904 continued to use the earlier unit until 1974 when an internal valve body revision for part throttle kickdown was used until mid 1978, and the V-8 part throttle kickdown was then used. Part throttle kickdown first appeared in some trucks in 1973.
The 1971 and later unit differs from the earlier version with the inclusion of a limit valve which limits the maximum road speed to about 35-50 mph, depending on tire size, at which part throttle kickdown action can occur. The later unit also requires less throttle opening than the earlier unit to trigger part throttle kickdown.
The part throttle kickdown unit mounts in place of governor plug end plate on the 1967 - 1970 valve body. The governor plug end plate is shown in the following image:
Using the Early Slant Six A904 Part Throttle Kickdown
1967 - 1970 727 transmissions can be modified using the early A904/Slant Six factory parts by replacing the governor plug end plate with the part throttle kickdown unit. 1971 and later transmissions that do not have part throttle kickdown and use the earlier style valve body with a four-screw shuttle valve cover plate, such as shown in the following image, can also use this part throttle kickdown unit.
The early part throttle kickdown unit cannot be used on 1971 and later transmissions with the later style part throttle kickdown unit and upper valve body which has a six-screw shuttle valve cover plate and uses the later part throttle kickdown unit.
The early A904/Slant Six unit replaces the governor plug end plate with its housing, plug, and longer screw. Two of the original screws are reused. The following image shows the components:
Photo courtesy of Pat Blais, aka. Torqueflite Patty
Using the 1971 and Later Part Throttle Kickdown
1967 - 1970 727 transmissions can be modified using the 1971 and later factory parts by replacing the governor plug end plate with the part throttle kickdown unit.
The 1971 and later part throttle kickdown unit is more complex than the earlier version but mounts in the same spot on the 1967 - 1970 valve body. The later unit will function the same as the earlier unit, but the limit valve which limits the maximum road speed will not function due to the other differences in the upper valve body.
The 1971 and later part throttle kickdown unit replaces the governor plug end plate with its housing, throttle plug, limit valve, limit valve spring, limit valve retainer, cover plate, thin head screw, and three longer screws. The following image shows the components:
Photo courtesy of Pat Blais, aka. Torqueflite Patty
The part throttle kickdown unit assembles as shown in the following diagram:
Note that one screw in the separator plate to transfer plate must be replaced with a thinner head screw to clear the unit’s housing. This screw position is not used on the later valve body. The screw to be replaced is shown in the following image:
Part Throttle Kickdown for 1966 and 1962 - 1965 Transmissions
1966 Transmissions
The 1966 valve body does not contain the pressure port to support the part throttle kickdown components. The upper valve body can be changed to a 1967 - 1970 unit to allow addition of the part throttle kickdown.
1962 - 1965 Transmissions
The 1962 - 1965 valve body does not contain the pressure port to support the part throttle kickdown components. The upper valve body can be changed to a 1967 - 1968 unit to allow addition of the part throttle kickdown. Later valve bodies do not have the provisions for the rear pump check valves. Additionally, a bushing, 1/2 inch outer diameter with 5/16 inch inner diameter, is required to fit the earlier manual gear selector into the later upper valve body.
NOTE: One screw in the separator plate must be replaced with a thinner head screw to clear the unit’s housing as shown in the following image with the unit installed:
