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TURBO HYDRA-MATIC 4 0 0 AUTOMATIC TRANSMISSION
7A4-3
TER
2573
Fig.
7A4-3
Converter Operation
and turbine are being driven at approximately the same speed
-
or at one-to-one ratio.
A hydraulic system, pressurized by a gear-type pump,
provides the working pressure required to operate the friction
elements
and
automatic
controls.
External
control
connections to transmission are:
Manual Linkage
-
To select the desired operating
range.
Engine Vacuum
-
To operate a vacuum modulator
unit.
12 Volt Electrical Signal
-
To operate an electrical
detent solenoid and TCS switch.
Approximate gear or torque ratios of the transmission
are as follows:
First
-
2.5 gear ratio X
2.00 converter stall ratio
..........................................
5:l
*Second
-
1.5 gear ratio
..........................................
1.51
*Third
...........................................................................
1
:
1
Reverse
-
2:l gear ratio X
2.00 converter stall ratio
........................................
4:l
*Second and third are also multiplied.
A vacuum modulator is used to automatically sense any
change in the torque input to the transmission. The vacuum
modulator transmits this signal to the pressure regulator for
line pressure control, to the 1-2 accumulator valve and to the
shift valves so that all torque requirements and shift speed
requirements of the transmission are met and smooth shifts
are obtained at all throttle openings.
The detent solenoid is activated by an electric switch on
the firewall. When the throttle is fully opened, the switch is
closed, activating the detent solenoid and causing the
transmission to downshift at speeds below approximately 70
mph.
PLANETARY GEAR TRAIN
A planetary gear train (Fig. 7A4-2) consists of three
2. A planet carri'er with four planet pinion gears.
members:
3. An internal gear.
1. A sun gear.
The sun gear is surrounded by and meshes with the
planet pinion gears, which rotate freely on pins attached to
a common support called the planet carrier. An internal gear
surrounds the assembly and meshes with the planet pinion
gears.
DIAGNOSIS
I. PRELIMINARY CHECKING
opens, exhaust gas enters the intake manifold which lowers
PROCEDURE
intake manifold vacuum. When intake manifold vacuum is
lowered, the transmission line oil pressure raises accordingly,
and may go above the upper specification limit. For this
reason, if high line pressures are obtained, proceed as follows:
IF LINE PRESSURES ARE INITIALLY
HIGH:
1. Disconnect the EGR vacuum line at the EGR valve
and plug the vacuum line.
Engines With EGR Valves
2. Recheck line pressures as indicated on the Preliminary
Checking Procedure Chart (Fig. 7A4-4).
On some engines with Exhaust Gas Recirculation
(EGR), the throttle is open enough in "Drive" range 1000
3. If high line pressures are still obtained, continue
rpm to cause the EGR valve to open. When the EGR valve
below.
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