so you already have a car with an automatic, or want one which only comes with a "slushbox" (so named because the engine's power has to travel through "slush," or, more accurately, oil). What can you do? Most people do not want to retrofit their car with a manual, or can't. Hence the shift kit for better shifts, and the manual valve body for "manumatics." Or, as Ean Orsel wrote...
Manual Valve Body: Turns your auto tranny into a partial-manual tranny.
Shift Kit: Makes your auto tranny do the exact same thing it does now, but better.
(There does not appear to be a manual valve body for the four-speed electronic automatic used by current Chrysler, Dodge, and Plymouth front-wheel-drive vehicles, since it does not have a valve body as such, according to Damien Civiello.)
Shift kits
Steve Knickerbocker wrote that "Smooth shifting transmissions accomplish [smoother shifting] by being in two gears at once when shifting up. It's known as shift overlap. Shift kits reduce or eliminate the shift overlap and speed up actuation of the shift, hence the harder feel to the shift. A shift kit will reduce wear because you won't have the trans trying to be in two gears at once."
Ross Bond wrote: "A firm shift is best for the transmission, the biggest problem with the 604, is the clutches are slipped so much between shifts, which gives you a very smooth shift, but makes lots of heat and wears out the seals and clutches a lot faster. Also 1994 and older cars are running on software in the controller which is bad for the transmission. They have what is called EMCC, this means an electrically modulated converter clutch, which partially locks up the torque converter to reduce slippage and fuel economy loss in the lower gears, but think about the heat that the converter clutch is making when it is partially applied. Which in turn kills the seals in the transmission. Some controllers are flashable and some are not. You can update to the newer ones in an older vehicle." ... "you can tell if the controller is flashable by looking at it. It is usually on the pass fenderwell. If it has cooling fins on the side of it, it is flashable. "
There appears to be a shift kit for the A-604/Ultradrive transmission, which seems to be based on replacing or upgrading the current computer. Damien Civillo wrote:
As I understood the shift kit it was similar to one for a standard transmission in that it replaced/modified some of the parts in the stock valve body so that the fluid flow is different. In other words, since the valves monitor/control fluid flow in the valvebody (the valves are electronic rather then hydraulic) this kit changed the way fluid flows through the valve body so that it modifies the input signals and tricks the tranny into behaving differently. Sort of like the boost bleed switches that some people rig up. We're just tricking the tranny into thinking that something else is happening when it's not.
