Chevrolet Silverado / GMC Sierra. Manual — part 1013
4. Use the scan tool to inspect for any active or stored diagnostic trouble codes.
5. Inspect the manual linkage at the transmission for proper function.
6. Turn the engine OFF.
7. Remove the pressure plug.
8. Install the J 21867 .
9. Access the Scan Tool Output Control for the PC Solenoid.
10. Start the engine.
11. Begin commanding PC Solenoid at 1.0 amp and lower the amperage in one-tenth increments
(0.01) until maximum line pressure is achieved.
12. Allow the pressure to stabilize between increments.
13. Compare your pressure readings to the Line Pressure table. Refer to Line Pressure .
14. If the pressure readings vary greatly from the line pressure table, refer to Oil Pressure
High or Low.
15. Turn the engine OFF.
16. Remove the J 21867 .
17. Install the pressure plug.
Tighten: Tighten the pressure plug to 8-14 N.m (6-10 lb ft).
IMPORTANT: It may be necessary to remove or disconnect components in
order to gain access to the transmission line pressure test
port/plug.
IMPORTANT: In order to achieve accurate line pressure readings, the
following procedure must be performed at least three times
in order to gather uniform pressure readings.
The scan tool is only able to control the PC solenoid in PARK
and NEUTRAL with engine speeds below 1500 RPM. This
protects the clutches from extreme high or low line
pressures.
This test must be preformed at 1200 RPM, between 38-93°C
(100-200°F).
NOTE:
Refer to Fastener Notice .
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
ROAD TEST
The following test provides a method of evaluating the condition of the automatic transmission.
The test is structured so that most driving conditions would be achieved. The test is divided into
the following parts:
Electrical Function Check
Upshift Control and Torque Converter Clutch (TCC) Apply
Part Throttle Detent Downshifts
Full Throttle Detent Downshifts
Manual Downshifts
Coasting Downshifts
Manual Gear Range Selection
REVERSE
Manual FIRST
Manual SECOND
Manual THIRD
Before the road test, ensure the following:
The engine is performing properly.
Transmission fluid level is correct. Refer to the Transmission Fluid Check.
Tire pressure is correct.
During the road test:
Perform the test only when traffic conditions permit.
Operate the vehicle in a controlled, safe manner.
Observe all traffic regulations.
View the scan tool data while conducting this test.
IMPORTANT: The Road Test Procedure should be performed only as part of the
Symptom Diagnosis. Refer to Symptoms - Automatic
Transmission.
IMPORTANT: Complete the test in the sequence given. Incomplete testing
cannot guarantee an accurate evaluation.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Take along qualified help in order to operate the vehicle safely.
Observe any unusual sounds or smells.
After the road test, check the following:
Transmission fluid level-Refer to the Transmission Fluid Check.
Diagnostic trouble codes (DTCs) that may have set during the testing-Refer to the
applicable DTC.
Scan tool data for any abnormal readings or data.
ELECTRICAL FUNCTION CHECK
Perform this check first, in order to ensure the electronic transmission components are connected
and functioning properly. If these components are not checked, a simple electrical condition
could be mis-diagnosed.
1. Connect the scan tool.
2. Ensure the gear selector is in PARK and set the parking brake.
3. Start the engine.
4. Verify that the following scan tool data can be obtained and is functioning properly.
Refer to Transmission Control Module Scan Tool Information (4L60-E) or
Transmission Control Module Scan Tool Information (6L50/6L80/6L90) for typical
data values. Data that is questionable may indicate a concern.
Engine speed
Transmission output speed
Transmission input speed - some models
Vehicle speed
TFP manual valve position switch
Transmission range
Commanded gear
PC solenoid reference current
PC solenoid actual current
PC solenoid duty cycle
Engine coolant temperature
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Transmission fluid temperature
Throttle angle
Ignition voltage
1-2 shift solenoid
2-3 shift solenoid
TCC solenoid duty cycle
TCC slip speed
5. Check the garage shifts.
1. Apply the brake pedal and ensure that the parking brake is set.
2. Move the gear selector through the following ranges:
1. PARK to REVERSE
2. REVERSE to NEUTRAL
3. NEUTRAL to DRIVE
3. Pause 2-3 seconds in each gear position.
4. Verify the gear engagements are immediate and not harsh.
IMPORTANT: Harsh engagement may be caused by any of the following
conditions:
High idle speed-Compare engine idle speed to desired
idle speed.
Commanded low PC solenoid current-Compare PC
solenoid reference current to PC solenoid actual current.
A default condition caused by certain DTCs that result in
maximum line pressure to prevent slippage
Low transmission fluid temperature
IMPORTANT: Soft or delayed engagement may be caused by any of the
following conditions:
Low idle speed-Compare engine idle speed to desired
idle speed.
Low fluid level
Commanded high PC solenoid current-Compare PC
solenoid reference current to PC solenoid actual current.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
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