Chevrolet 10 Series 1970 Service Manual page 477

TURBO HYDRA-MATIC 400 TRANSMISSION
General D es crip tio n ................................................................................... 7-47
Maintenance and A d ju stm e n ts............................................................ ..... 7-48
Transmission F l u i d ................................................................................. 7-48
Fluid Checking Procedure .............................................................. ..... 7-48
Fluid Level I n d ic a t o r ....................................................................... ..... 7-49
Shift C ontrol Linkage A d ju s tm e n t................................................. ..... 7-49
Detent Sw itch A d ju s tm e n t.............................................................. ..... 7-50
Neutral Safety Sw itch A d ju s tm e n t................................................. ..... 7-50
Draining and R efillin g T ra n sm ission .................................................... 7-50
Pressure Regulator Valve ................................................................ ..... 7-51
C ontrol Valve B ody ......................................................................... ..... 7-51
Governor ........................................................................................... ..... 7-51
Modulator and M odu lator V a lv e ..................................................... ..... 7-51
Parking L in k a g e ................................................................................ ..... 7-51
The Turbo H ydra-M atic 400 transm ission is a fu lly
automatic unit consisting p rim a rily of a 3 -elem ent hy­
draulic torque co n verter and a compound planetary gear
set. T h ree m u ltip le-d isc clutches, one sprag unit, one
r o lle r clutch, and two bands provid e the fric tio n elem ents
requ ired to obtain the d esired function of the compound
planetary gear set.
The torque co n verter couples the engine to the plane­
ta ry gea rs through o il and provid es hydraulic torque
m ultiplication when required.
g e a r set produces three fo rw a rd speeds and re v e rs e .
The 3 -elem ent torque con verter consists of a pump or
d rivin g m em ber, a turbine or driven m em ber, and a sta­
tor assem bly. The stator is mounted on a one-way r o lle r
clutch which w ill allow the stator to turn clockw ise but
not counter-clockw ise.
The torque con verter housing is fille d with o il and is
attached to the engine crankshaft by a fle x plate and al­
ways rotates at engine speed.
an in tegra l part of the con verter housing, th erefo re the
pump blades, rotating at engine speed, set the o il within
the con verter into motion and d ire c t it to the turbine,
causing the turbine to rotate.
A s the o il passes through the turbine it is travelin g in
such a direction that if it w e re not r e -d ire c te d by the
stator it would hit the re a r of the co n verter pump blades
and impede its pumping action. So at low turbine speeds,
the o il is r e -d ire c te d by the stator to the co n verter pump
in such a manner that it actually a ssists the con verter
pump to d e liv e r pow er o r m ultiply engine torque.
A s turbine speed in crea ses, the direction of the oil
leavin g the turbine changes and flow s against the rea r
side of the stator vanes in a clockw ise direction. Since
the stator is now im peding the smooth flow of oil, its
r o lle r clutch re le a s e s and it re v o lv e s fr e e ly on its shaft.
Once the stator becom es inactive, there is no further
m ultiplication of engine torque within the con verter. At
this point, the con verter is m e re ly acting as a fluid
coupling as both the co n verter pump and turbine are being
d riven at approxim ately the sam e speed - o r at one-to-
one ratio.
A hydraulic system p re s s u rize d by a gear type pump
p rovid es the working p ressu re requ ired to operate the
NDEX
Page
GENERAL DESCRIPTION
The compound planetary
The co n verter pump is
CLUTCHES AND TRANSMISSIONS 7-47
Rear Seal ...........................................................................................
O ther Service O p e ra tio n s...................... ..............................................
Transmission Replacement ................................................................
Turbo Hydra-Matic 400 Diagnosis Procedure
Sequence ...........................................................................................
O il Level and Condition C h e c k ........................................................
Manual Linkage ................................................................................
O il Leaks ...........................................................................................
Case P o ro sity-R e p a ir .......................................................................
Oil Pressure C h e c k ...........................................................................
Vacuum M odulator Assembly .......................................................
Pressure Switch C h e c k .....................................................................
Transmission Shift P o in ts ................................................................
fric tio n elem ents and automatic controls.
External control connections to transm ission are:
Manual Linkage - T o s e le c t the desired operating
Engine Vacuum - T o operate a vacuum modula­
12 V olt E le c tric a l - T o operate an e le c tr ic a l de­
A vacuum modulator is used to autom atically sense any
change in the torque input to the transm ission. The vacu­
um modulator transm its
regu lator fo r line pressu re control, to the 1-2 accumu­
la tor valve, and to the shift va lves so that all torque r e ­
quirem ents of the transm ission are met and smooth
shifts are obtained at a ll throttle openings.
The detent solenoid is activated by an e le c tr ic switch
on the carburetor. When the throttle is fully opened, the
switch on the carbu retor is closed, activating the detent
solenoid and causing the transm ission to downshift fo r
passing speeds.
The s e le c to r quadrant has s ix se le c to r positions: P,
R, N, D, L2, L I .
P . - P A R K position p o sitively locks the output shaft to
the transm ission case by means of a locking pawl
to prevent the veh icle fro m rollin g in either d ir e c ­
tion. The engine may be started in P ark position.
NOTE:
P a rk position is not provided fo r 30 Series
Truck.
R. - REVERSE enables the vehicle to be operated in a
re v e rs e direction.
N. - N eutral position enables the engine to be started
and run without drivin g the vehicle.
D. - DRIVE Range is used fo r a ll norm al drivin g condi­
tions and maximum
three gear ratios, fro m the starting ratio to d irect
d rive. Detent downshifts are available by d ep ress­
ing the a c c e le ra to r to the flo o r.
L2 - L2 Range has the
Range, but prevents the transm ission fro m shifting
above second speed to retain second speed a c c e le ­
ration when ex tra
Range can also be used fo r engine braking.
.................................
range.
tor unit.
tent solenoid.
this signal to the p ressu re
economy. D rive Range has
same starting ratio as D rive
perform ance is desired.
CHEVROLET TRUCK SERVICE MANUAL
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L2
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