Chevrolet Silverado / GMC Sierra. Service 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