Chevrolet 10 Series 1970 Service Manual page 468

CLUTCHES AND TRANSMISSIONS 7-38
TURBO HYDRA-MATIC 3 5 0 TRANSM ISSION
General D e s c rip tio n ..............................................................................
Maintenance and A d ju stm e n ts............................................................
Oil Level Check ................................................................................
Periodic O il Change .........................................................................
Manual Shift Linkage Check and A d ju stm e n t...............................
Detent Cable A d ju s tm e n t................................................................
Transmission Replacem ent .................................................................
Other Service O p e ra tio n s.....................................................................
The purpose of a tran sm ission is to p rovid e suitable
gear ratios between the engine and re a r wheels fo r all
drivin g conditions. The Turbo H yd ra -M a tic 350 is a fu lly
automatic 3 -speed transm ission encased in a tw o-p iece
aluminum casting (m ain
transm ission consists p r im a r ily of a hydraulic torque
co n verter and compound
m u ltip le-d isc clutches, two r o lle r clutch assem blies, and
one band p rovid e the fric tio n elem ents requ ired to obtain
the d esired function of the planetary gear set.
The torque c o n verter is
couples the engine to the planetary gea rs through o il
and p rovid es hydraulic torque m ultiplication when r e ­
quired. The compound planetary gear set produces three
fo rw a rd speeds and r e v e r s e .
The hydraulic system , p re s s u rize d by a gea r type
pump, p rovides the w orking p ressu re
era te the fric tio n elem ents and automatic controls.
The vacuum m odulator is of the aneriod type and is
used to autom atically sense any change in torque input to
the transm ission. It transm its this signal to the p ressu re
regulator, to the in term ediate clutch accum ulator valve,
and to the shift va lv e s so that a ll torques and shift speed
requirem ents of the transm ission are met and smooth
shifts a re obtained at a ll throttle openings and altitude
conditions.
The cable operated detent system is designed to ensure
p o sitive part throttle or fu ll throttle downshifting depend­
ing on throttle position.
External con trol connections to transm ission are:
Manual Linkage - T o s e le c t the d e s ire d operating
range.
Engine Vacuum - To operate the vacuum modulator.
Detent Cable - T o operate Detent System.
The Turbo H yd ra-M atic
three fo rw a rd d rivin g ranges, which can be selected with
the shift le v e r.
Approxim ate gear ratios of the transm ission are as
follow s:
OIL LEVEL CHECK
The transm ission o il le v e l should be checked p erio d ­
Page
7-38
7-38
7-38
7-39
7-39
7-40
7-40
7-42
GENERAL DESCRIPTION
housing and extension). The
planetary gear set. Four
a sim ple transm ission that
req u ired to op­
350 tran sm ission featu res
MAINTENANCE AND ADJUSTMENTS
IN D E X
Turbo Hydra-Matic Diagnosis P r o c e d u r e .......................................... ...... 7-42
Sequence ........................................................................................... ...... 7-42
Oil Level and C ondition C h e c k .............................................................. 7-42
Manual Linkage ................................................................................ ...... 7-42
O il Leaks ........................................................................................... ...... 7-43
Case Porosity Repair ....................................................................... ...... 7-43
Vacuum M odulator Checks
Transmission Shift P o in t s ................................................................ ...... 7-45
F IR S T - 2.5:1
IN T E R M E D IA T E - 1.5:1
D IR E C T - 1.00:1
REVERSE - 2.00:1
The s e le c to r quadrant has six s e le c to r positions -
P, R, N, D, L 2 , L j.
P - P A R K position p o s itiv ely locks the output shaft to the
transm ission case, by means of a locking pawl, to
preven t the veh icle fro m ro llin g in eith er direction .
This position should be se le cte d w henever the d riv e r
lea ves the veh icle.
P a rk position.
R - REVERSE enables the veh icle to be operated in a r e ­
v e rs e direction.
N - N E U T R A L position enables the engine to be started
and run without m oving the veh icle.
D - D RIVE RANGE, used fo r a ll norm al d rivin g condi­
tions and maximum economy, has three gea r ratios.
Detent downshifts are available fo r safe passing, by
d epressing the a c c e le ra to r to the flo o r.
L i ~ L j RANG E can be selected at any v e h icle speed.
When selected at speeds o v e r 50 mph, the tran s­
m ission w ill shift to second gea r and rem ain in
second until ve h icle speed is reduced to approxi­
m ately 50 mph (depending on axle ra tio ) b efo re
shifting to fir s t gear.
L t Range position
fro m shifting out of fir s t gear. This is p a rticu la rly
ben eficia l fo r maintaining maximum engine braking
when continuous fir s t gear operation is desirab le.
L 2 - L 2 RANG E fo r
L 2 Range has the same starting ratio as D rive
Range, but prevents the transm ission fro m shifting
above second gear.
celera tion when extra p erform a n ce is desired, and
can also be used fo r engine braking.
L 2 Range can be selected at any veh icle speed,
and the transm ission w ill shift to second gear, and
rem ain in second until the v eh icle
throttle opening is changed to obtain fir s t gea r op­
eration, in the sam e manner as in D rive Range.
ic a lly as recom m ended in Section 0. O il should be added
only when le v e l is on o r below the " ADD" m ark on the
dip stick with o il hot or at operating tem peratu re. The o il
............................................................ ...... 7-44
The engine m ay be started in
prevents the tran sm ission
congested tr a ffic o r h illy terra in .
This retains second speed ac­
speed o r the
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