Jeep Wrangler 1997 Manual - page 985
clutch. Torque multiplication is created when the sta-
tor directs the hydraulic flow from the turbine to
rotate the impeller in the direction the engine crank-
shaft is turning. The turbine transfers power to the
planetary gear sets in the transmission. The transfer
of power into the impeller assists torque multiplica-
tion. At low vehicle speed, the overrunning clutch
holds the stator (during torque multiplication) and
allows the stator to free wheel at high vehicle speed.
The converter clutch provides reduced engine speed
and greater fuel economy when engaged. Clutch
engagement also provides reduced transmission fluid
temperatures. The converter clutch engages in third
gear. The torque converter hub drives the transmis-
sion oil (fluid) pump.
The torque converter is a sealed, welded unit that
is not repairable and is serviced as an assembly.
CAUTION: The torque converter must be replaced if
a transmission failure resulted in large amounts of
metal or fiber contamination in the fluid. If the fluid
is contaminated, flush the fluid cooler and lines.
TRANSMISSION GEAR RATIOS
Forward gear ratios are:
•
2.74:1 (first gear)
•
1.54:1 (second gear)
•
1.00:1 (third gear)
GEARSHIFT MECHANISM
The shift mechanism is cable operated and pro-
vides six shift positions. The shift indicator is located
on the console next to the gear shift. The shift posi-
tions are:
•
Park (P)
•
Reverse (R)
•
Neutral (N)
•
Drive (D)
•
Manual Second (2)
•
Manual Low (1)
Manual low (1) range provides first gear only. Over
run braking is also provided in this range. Manual
second (2) range provides first and second gear only.
Drive range provides first, second, and third gear
ranges.
DESCRIPTION AND OPERATION
HYDRAULIC CONTROL SYSTEM
The transmission hydraulic control system per-
forms four basic functions.
•
pressure supply
•
pressure regulation
•
flow control and lubrication
•
clutch/band application
PRESSURE SUPPLY
The oil pump develops fluid pressure for clutch/
band application and for lubrication. The pump is
driven by the torque converter. The converter is
driven by a driveplate attached to the engine crank-
shaft.
Pressure Regulation
The pressure regulator valve maintains line (oper-
ating) pressure. The amount of pressure developed is
controlled by throttle pressure which is dependent on
the degree of throttle opening. The regulator valve is
located in the valve body.
The throttle valve determines throttle pressure
and shift speed. Governor pressure increases in pro-
portion to vehicle speed. The throttle valve controls
upshift and downshift speeds by regulating pressure
according to throttle position.
Flow Control And Lubrication
The manual valve is operated by the gearshift link-
age and provides the operating range selected by the
driver.
The switch valve controls line pressure to the con-
verter clutch. The valve also directs oil to the cooling
and lubrication circuits. The switch valve regulates
oil pressure to the torque converter by limiting max-
imum oil pressure to 130 psi.
The 1-2 shift valve provide 1-2 and 2-1 shifts and
the 2-3 shift valve provide 2-3 and 3-2 shifts.
The 1-2 shift control valve transmits 1-2 shift pres-
sure to the accumulator piston. This controls kick-
down
band
capacity
on
1-2
upshifts
and
3-2
downshifts.
The 2-3 valve throttle pressure plug provides 3-2
downshifts at varying throttle openings depending on
vehicle speed.
The kickdown valve provides forced downshifts
depending on vehicle speed. Downshifts occur when
the throttle is opened beyond downshift detent posi-
tion. Detent is reached just before wide open throttle
position.
The limit valve determines maximum speed at
which a 3-2 part throttle kickdown can be made.
Some transmissions do not have the limit valve and
maximum speed for a 3-2 kickdown is at the detent
position.
The shuttle valve has two functions. First is fast
front band release and smooth engagement during
“lift foot” 2-3 upshifts. Second is to regulate front
clutch release and band application during 3-2 down-
shifts.
The fail safe valve restricts feed to the converter
clutch if front clutch pressure drops. It permits
clutch engagement only in direct (third) gear and
provides fast clutch release during kickdown.
TJ
TRANSMISSION AND TRANSFER CASE
21 - 79
GENERAL INFORMATION (Continued)