Chevrolet Silverado / GMC Sierra. Manual — part 1015
3. Verify that there is no noticeable slip, noise or vibration.
Manual First
1. With the vehicle stopped, move the gear selector to FIRST.
2. Accelerate the vehicle to 32 km/h (20 mph).
3. Verify the following:
No upshifts occur.
The TCC does not apply.
There is no noticeable slip, noise, or vibration.
Manual Second
1. With the vehicle stopped, move the gear selector to SECOND.
2. Accelerate the vehicle to 57 km/h (35 mph).
3. Verify the following:
The 1-2 shift occurs.
The 2-3 shift does not occur.
There is no noticeable slip, noise or vibration.
Manual Third
1. With the vehicle stopped, move the gear selector to THIRD.
2. Accelerate the vehicle to 64 km/h (40 mph).
3. Verify the following:
The 1-2 shift occurs.
The 2-3 shift occurs.
There is no noticeable slip, noise or vibration.
TORQUE CONVERTER DIAGNOSIS
The torque converter clutch (TCC) is applied by fluid pressure, which is controlled by a pulse
width modulation (PWM) solenoid valve. This solenoid valve is located inside of the automatic
transmission assembly. The solenoid valve is controlled through a combination of computer
controlled switches and sensors.
TORQUE CONVERTER STATOR
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
The torque converter stator roller clutch can have 2 different malfunctions.
The stator assembly freewheels in both directions.
The stator assembly remains locked up at all times.
POOR ACCELERATION AT LOW SPEED
If the stator is freewheeling at all times, the vehicle tends to have poor acceleration from a
standstill. At speeds above 50-55 km/h (30-35 mph), the vehicle may act normally. For poor
acceleration, you should first determine that the exhaust system is not blocked, and the
transmission is in First gear when starting out.
If the engine freely accelerates to high RPM in NEUTRAL, you can assume that the engine and
the exhaust system are normal. Check for poor performance in DRIVE and REVERSE to help
determine if the stator is freewheeling at all times.
POOR ACCELERATION AT HIGH SPEED
If the stator is locked up at all times, performance is normal when accelerating from a standstill.
Engine RPM and vehicle speed are limited or restricted at high speeds. Visual examination of the
converter may reveal a blue color from overheating.
If the converter has been removed, you can check the stator roller clutch by inserting a finger into
the splined inner race of the roller clutch and trying to turn the race in both directions. You
should be able to freely turn the inner race clockwise, but you should have difficulty in moving
the inner race counterclockwise or you may be unable to move the race at all.
NOISE
You may notice a torque converter whine when the vehicle is stopped and the transmission is in
DRIVE or REVERSE. This noise will increase as you increase the engine RPM. The noise will
stop when the vehicle is moving or when you apply the torque converter clutch, because both
halves of the converter are turning at the same speed.
Perform a stall test to make sure the noise is actually coming from the converter:
1. Place your foot on the brake.
IMPORTANT: Do not confuse this noise with pump whine noise, which is
usually noticeable in PARK, NEUTRAL and all other gear ranges.
Pump whine will vary with line pressure.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
2. Put the gear selector in DRIVE.
3. Depress the accelerator to approximately 1,200 RPM for no more than six seconds.
A torque converter noise will increase under this load.
TORQUE CONVERTER CLUTCH SHUDDER
The key to diagnosing TCC shudder is to note when it happens and under what conditions.
TCC shudder which is caused by the transmission should only occur during the apply or the
release of the converter clutch. Shudder should never occur after the TCC plate is fully applied.
IF SHUDDER OCCURS DURING TCC APPLY OR RELEASE
If the shudder occurs while the TCC is applying, the problem can be within the transmission or
the torque converter. Something is causing one of the following conditions to occur:
Something is not allowing the clutch to become fully engaged.
Something is not allowing the clutch to release.
The clutch is releasing and applying at the same time.
One of the following conditions may be causing the problem to occur:
Leaking turbine shaft seals
A restricted release orifice
A distorted clutch or housing surface due to long converter bolts
Defective friction material on the TCC plate
IF SHUDDER OCCURS AFTER TCC HAS APPLIED
If shudder occurs after the TCC has applied, most of the time there is nothing wrong with the
transmission.
The TCC is not likely to slip after the TCC has been applied. Engine problems may go unnoticed
under light throttle and load, but they become noticeable after the TCC apply when going up a
hill or accelerating. This is due to the mechanical coupling between the engine and the
NOTE:
You may damage the transmission if you depress the
accelerator for more than 6 seconds.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
transmission.
Once TCC is applied, there is no torque converter (fluid coupling) assistance. Engine or driveline
vibrations could be unnoticeable before TCC engagement.
Inspect the following components in order to avoid misdiagnosis of TCC shudder. An inspection
will also avoid the unnecessary disassembly of a transmission or the unnecessary replacement of a
torque converter.
Spark plugs-Inspect for cracks, high resistance or a broken insulator.
Plug wires-Look in each end. If there is red dust (ozone) or a black substance (carbon)
present, then the wires are bad. Also look for a white discoloration of the wire. This
indicates arcing during hard acceleration.
Coil-Look for a black discoloration on the bottom of the coil. This indicates arcing while
the engine is misfiring.
Fuel injector-The filter may be plugged.
Vacuum leak-The engine will not get a correct amount of fuel. The mixture may run rich or
lean depending on where the leak occurs.
EGR valve-The valve may let in too much or too little unburnable exhaust gas and could
cause the engine to run rich or lean.
MAP/MAF sensor-Like a vacuum leak, the engine will not get the correct amount of fuel for
proper engine operation.
Carbon on the intake valves-Carbon restricts the proper flow of air/fuel mixture into the
cylinders.
Flat cam-Valves do not open enough to let the proper fuel/air mixture into the cylinders.
Oxygen sensor-This sensor may command the engine too rich or too lean for too long.
Fuel pressure-This may be too low.
Engine mounts-Vibration of the mounts can be multiplied by TCC engagement.
Axle joints-Check for vibration.
Thorttle position (TP) Sensor-The TCC apply and release depends on the TP Sensor in
many engines. If the TP Sensor is out of specification, TCC may remain applied during
initial engine loading.
Cylinder balance-Bad piston rings or poorly sealing valves can cause low power in a
cylinder.
Fuel contamination-This causes poor engine performance.
Replace the torque converter if any of the following conditions exist:
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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