Toyota Modified Valve Body

As many Toyota and Jeep owners know, the AW4 / Toyota 340,
A340, and A341E series of transmissions are generally very
well made and demonstrate excellent durability in unmodified
applications. The framework is present for an extremely
strong transmission that is to be used in a high performance
or extreme duty application.

The problem is that the original calibration is engineered
for driver comfort rather than ultimate component strength.
The soft, sliding shifts that are part of the original
design are not appropriate for increased horsepower
applications, towing, off road use, racing, etc.

These calibration inadequacies quickly manifest themselves
as extremely poor shift quality, and more often than not,
severe damage to the gearbox is soon to follow. One of the
most common symptoms of this is the engine stuttering or
hitting the rev limiter during a full throttle upshift.

Without going into too much technical detail, the factory
shortcomings can be addressed through modification and
recalibration of the control valve assembly, a.k.a. the
valve body.

The valve body is a component that is comprised of valves,
solenoids, an orifice separator plate and an intricate
series of passages- it is the most complex component in the
most complex part of your vehicle- the automatic

The function of the valve body is to act as the “brain” of
the automatic transmission- it directs hydraulic pressure to
the appropriate clutches and bands at the right time to
initiate upshifts, down shifts, selection of reverse,
converter clutch application, etc. As well as controlling
shift timing and shift quality, it is also responsible for
directing hydraulic pressure to the cooler and the
lubrication circuit.

As you can imagine, the transmission’s operational
characteristics can be drastically altered and also
customized to the given application through modifications to
this component.

Because there are no commercially available shift kits for
these transmissions, we began working on valve body
modifications that were appropriate for Supras, Jeeps with
the AW4 transmission, Toyota Tundra, Tacoma and 4Runner, and
also Lexus SUV’s and rear drive passenger cars- especially
those that needed to handle the additional power that
accompanies the installation of a supercharger, turbo or
nitrous oxide injection. van điều khiển khí nén

At the risk of oversimplification, there are a few things
that are done in concert to create much more favorable
operation of the gearbox.

The first thing that needs to be done is to increase the
hydraulic operating pressure of the transmission- this
pressure is known as “line pressure”. All hydraulic
functions of the transmission are based on this pressure-
what is especially of concern for these purposes is the
clamping force which is applied to the clutches and bands to
get them to hold against engine torque.

In simple terms, increased engine output is complemented by
increased line pressure and increased “clamp” on the
clutches- this can be likened to a performance clutch with a
heavier pressure plate spring in a manual transmission
equipped vehicle.



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