Jeep Grand Cherokee WK. Manual — part 1477
First Gear Engaged
The TCM monitors the activation sequence via the speed of the input shaft, which slows down as the frictional
connection in the multiple-disc holding clutch increases. When the speed drops to the specified level, the TCM shuts
off the power to the 3-4 shift solenoid valve (10). The spring chamber of the shift valve B2 (9) is depressurized and
switches downwards. This connects the line to the opposing face of the piston B2 (6) with the pressure holding
valve (11). The pressure on the opposing face of the piston B2 (6) drops to a residual pressure.
The working pressure (p-A) is formed and travels via the 2-3 holding pressure shift valve, the 2-3 command valve
and the ball valve (16) to multi-plate clutch K3 (4) and via the 3-4 command valve (13) to the end face of the 3-4
shift pressure shift valve (14). The 3-4 shift pressure shift valve (14) is moved against the force of the spring
towards the right. At the same time the 3-4 solenoid valve (10) is energized. This allows shift valve pressure (p-SV)
to enter the spring chamber of the shift valve B2 (9) and to reach the end face of the 3-4 command valve (13). The
shift valve B2 (9) is held in the upper position and the 3-4 command valve (13) switches towards the right. At the
end face of the 3-4 shift pressure shift valve (14) the working pressure (p-A) is replaced by shift valve pressure
(p-SV).
The 3-4 command valve (13) moves to the left. Working pressure (p-A) travels via the holding pressure shift valve
(12) and the 3-4 command valve (13) to the piston of multiple-disc holding clutch B2 (5).
1 - HOLDING CLUTCH B1
11 - PRESSURE HOLDING VALVE
2 - DRIVING CLUTCH K1
12 - 3-4 HOLDING PRESSURE SHIFT VALVE
3 - HOLDING CLUTCH B3
13 - 3-4 COMMAND VALVE
4 - DRIVING CLUTCH K3
14 - 3-4 SHIFT PRESSURE SHIFT VALVE
5 - HOLDING CLUTCH B2 PISTON
15 - 3-4 OVERLAP REGULATING VALVE
6 - HOLDING CLUTCH B2 PISTON OPPOSING FACE
16 - BALL VALVE
7 - SHIFT PRESSURE REGULATING SOLENOID
17 - 1-2/4-5 COMMAND VALVE
8 - SHIFT PRESSURE REGULATING VALVE
18 - 1-2/4-5 COMMAND VALVE
9 - SHIFT VALVE B2
19 - BALL VALVE
10 - 3-4 SHIFT SOLENOID
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AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION
WK
DIAGNOSIS AND TESTING
AUTOMATIC TRANSMISSION
CAUTION: Before attempting any repair on a NAG1 automatic transmission, check for Diagnostic Trouble
Codes with the appropriate scan tool.
Transmission malfunctions may be caused by these general conditions:
•
Poor engine performance.
•
Improper adjustments.
•
Hydraulic malfunctions.
•
Mechanical malfunctions.
•
Electronic malfunctions.
•
Transfer case performance (if equipped).
Diagnosis of these problems should always begin by checking the easily accessible variables: fluid level and con-
dition, gearshift cable adjustment. Then perform a road test to determine if the problem has been corrected or if
more diagnosis is necessary.
PRELIMINARY
Two basic procedures are required. One procedure for vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVABLE
1. Check for transmission fault codes using the appropriate scan tool.
2. Check fluid level and condition.
3. Adjust gearshift cable if complaint was based on delayed, erratic, or harsh shifts.
4. Road test and note how transmission upshifts, downshifts, and engages.
VEHICLE IS DISABLED
1. Check fluid level and condition.
2. Check for broken or disconnected gearshift cable.
3. Check for cracked, leaking cooler lines, or loose or missing pressure-port plugs.
4. Raise and support vehicle on safety stands, start engine, shift transmission into gear, and note following:
a. If propeller shaft turns but wheels do not, problem is with differential or axle shafts.
b. If propeller shaft does not turn and transmission is noisy, stop engine. Remove oil pan, and check for debris.
If pan is clear, remove transmission and check for damaged driveplate, converter, oil pump, or input shaft.
c. If propeller shaft does not turn and transmission is not noisy, perform hydraulic-pressure test to determine if
problem is hydraulic or mechanical.
ROAD TESTING
Before road testing, be sure the fluid level and control cable adjustments have been checked and adjusted if nec-
essary. Verify that all diagnostic trouble codes have been resolved.
Observe engine performance during the road test. A poorly tuned engine will not allow accurate analysis of trans-
mission operation.
Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage.
Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means clutch, overrunning clutch, or line pressure problems.
A slipping clutch can often be determined by comparing which internal units are applied in the various gear ranges.
The Clutch Application chart CLUTCH APPLICATION provides a basis for analyzing road test results.
WK
AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION
21 - 719
CLUTCH APPLICATION
GEAR
RATIO
B1
B2
B3
K1
K2
K3
F1
F2
1
3.59
X*
X
X*
X
X
2
2.19
X
X
X*
X
3
1.41
X
X
X
4
1.00
X
X
X
5
0.83
X
X
X
X*
N
N/A
X
X
R
3.16
X*
X
X
X
R - Limp
In or
4WD
Low
Range
1.93
X
X
X
* = The shift components required during coast.
AUTOMATIC TRANSMISSION
CONDITION
POSSIBLE CAUSES
CORRECTION
Harsh N-D Engagement
Harsh N-R Engagement
1. Transmission adaptation/
calibration.
1. Check for latest level TCM
software. Perform the TCM
adaptation procedure. (Refer to
8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/
TRANSMISSION CONTROL
MODULE - STANDARD
PROCEDURE)
2. Transmission in limp-home mode.
2. Check TCM for DTCs. Repair
as needed.
3. Driveline lash/movement.
3. Check engine mounts,
transmission mount, driveshaft
couplings, rear crossmember
mounts, axle mounts and axle
lash.
4. Converter clutch or lock up control
valve malfunction.
4. Perform converter clutch
diagnostics test. Inspect valve
body for stuck or sticky lock up
control valve. If valve motion is
free, replace lock up solenoid
and retest.
5. Valve Body Malfunction.
5. Inspect valve body for stuck
or sticky regulator valve.
6. Clutch or planetary component
damage.
6. Remove, disassemble and
repair transmission as
necessary.
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AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION
WK
CONDITION
POSSIBLE CAUSES
CORRECTION
Delayed N-D or N-R
Engagement
1. Transmission adaptation/
calibration.
1. Check for latest level TCM
software. Perform the TCM
adaptation procedure. (Refer to
8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/
TRANSMISSION CONTROL
MODULE - STANDARD
PROCEDURE)
2. Torque converter fluid drain back,
delayed soft engagement.
2. If vehicle moves normally
after 3 seconds of shifting into
gear, no repair is necessary. If
longer, inspect pump for worn
bushing.
3. Fluid Level Low.
3. Check and adjust fluid level.
(Refer to 21 - TRANSMISSION/
AUTOMATIC - NAG1/FILTER -
STANDARD PROCEDURE)
4. Filter plugged.
4. Check TC out pressure, if <
10psi, check for plugged filter.
Replace if needed.
5. Filter damaged or missing,
missing o-ring.
5. Check for damaged/missing
filter or cut/missing o-ring.
6. Valve Body Malfunction.
6. Inspect valve body for stuck/
sticky regulator valve or shift
group valves.
7. Oil pump gears worn/damaged.
7. Inspect pump for damage or
excessive clearances. Replace
if needed.
No Drive or Reverse
Engagement (vehicle will
not move)
1. Fluid level low.
1. Check and adjust fluid level.
(Refer to 21 - TRANSMISSION/
AUTOMATIC - NAG1/FILTER -
STANDARD PROCEDURE)
2. Misadjusted/damaged shift cable.
2. Inspect shift system. Adjust
and/or replace worn/damaged
parts.
3. Filter plugged.
3. Check TC out pressure, if <
10psi, check for plugged filter.
Replace if needed.
4. Filter damaged or missing,
missing filter o-ring.
4. Check for damaged/missing
filter or cut/missing o-ring.
5 Hydraulic system-Low/no line
pressure.
5. Remove valve body. Inspect
or sticky/stuck regulator valve.
If valve motion is free, replace
line pressure solenoid and
retest. If condition still exists
check for worn/damaged pump.
Replace pump assembly if
needed.
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AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION
21 - 721
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