Chevrolet Silverado / GMC Sierra. Manual — part 741
NOISE IN FIRST, SECOND, THIRD, FOURTH, FIFTH, OR REVERSE GEAR
NOISE IN FIRST, SECOND, SIXTH, OR REVERSE GEAR
NOISE IN SECOND OR SIXTH GEAR
Inspect for damaged low and reverse clutch piston
assembly (470), spring (469), spring retaining ring
(466), and center support assembly (459).
Inspect for damaged low clutch sprag assembly (467).
Holding the sprag assembly with the retaining ring
facing up, and the inner race of the sprag assembly
fixed, the outer race should freewheel
counterclockwise.
Inspect for cut, worn, or damaged low clutch sprag
seal (468).
Output Carrier Assembly (68)
Inspect for damaged or stripped splines on the output
carrier assembly.
Checks
Causes
Input Carrier Assembly (52)
Inspect thrust washers, pinion gears, and pins for wear or
damage.
Input Sun Gear (53)
Inspect for damaged sun gear.
1-2-3-4 and 3-5-R Clutch
Assembly (51)
Inspect for worn or damaged clutch bearing (428).
Checks
Causes
Center Support with 2-6 Low
and Reverse Clutch Assembly
(67)
Inspect for worn or damaged output carrier outer sun gear
shaft front and rear bushings (458 and 460).
Output Carrier Assembly (68)
Inspect for a worn or damaged center support roller
bearing assembly (485).
Checks
Causes
Center Support with 2-6 Low
and Reverse Clutch Assembly
(67)
Inspect for damaged or worn output carrier outer sun
gear shaft front bushing (458).
Inspect for damaged or worn output carrier outer sun
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
NOISE DURING 3-4 OR 4-3 SHIFTS
NOISE IN FOURTH, FIFTH, OR SIXTH GEAR
CLUTCH PLATE DIAGNOSIS
COMPOSITION PLATES
Dry the plates and inspect the plates for the following conditions:
Pitting
Flaking
gear shaft rear bushing (460).
Inspect for damaged 2-6 clutch backing plate (451).
Inspect for worn splines on backing plate.
Inspect for damaged 2-6 clutch backing plate
retaining ring (450).
Inspect for damaged 2-6 clutch piston assembly
(457), spring (456), retaining ring (455), and center
support assembly (459).
Checks
Causes
4-5-6 Clutch (with Output
Carrier Shaft and Dampener)
Hub Assembly (58)
Inspect hub assembly (475), dampener (476), and
apply plate (477) for wear or damage.
Inspect for damaged or worn 4-5-6 clutch backing
plate (432).
Checks
Causes
Input Sun Gear Thrust Washer
(55)
Inspect for wear or damage.
Turbine Shaft Thrust Bearing
Assembly (57)
Inspect for wear or damage.
4-5-6 Clutch (with Output
Carrier Shaft and Dampener)
Hub Assembly (58)
Inspect for damaged or worn 4-5-6 clutch backing
plate (432).
Inspect for improper selective 4-5-6 clutch backing
plate retaining ring (431).
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
Delamination-splitting or separation of bonded clutch material
Wear
Glazing
Cracking
Charring
Chips or metal particles embedded in the lining
Replace a composition plate which shows any of these conditions.
STEEL PLATES
Wipe the plates dry and check the plates for heat discoloration. If the surfaces are smooth, even if
color smear is indicated, you can reuse the plate. If the plate is discolored with heat spots or if the
surface is scuffed, replace the plate.
CAUSES OF BURNED CLUTCH PLATES
The following conditions can result in a burned clutch plate:
Incorrect usage of clutch or apply plates
Engine coolant or water in the transmission fluid
A cracked clutch piston
Damaged or missing seals
Low line pressure
Valve body conditions
The valve body face is not flat.
Porosity is between channels.
The valve bushing clips are improperly installed.
The checkballs are misplaced.
The Teflon® seal rings are worn or damaged.
ENGINE COOLANT/WATER IN TRANSMISSION
NOTE:
The antifreeze or water will deteriorate the seals, gaskets and the
glue that bonds the clutch material to the pressure plate. Both
conditions may cause damage to the transmission.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
If antifreeze or water has entered the transmission, perform the following:
1. Disassemble the transmission.
2. Replace all of the rubber type seals. The coolant will attack the seal material which will
cause leakage.
3. Replace the composition-faced clutch plate assemblies. The facing material may separate
from the steel center portion.
4. Replace all of the nylon parts - washers.
5. Replace the torque converter.
6. Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.
7. Flush the cooler lines after the transmission cooler has been properly repaired or replaced.
FLUID LEAK DIAGNOSIS
GENERAL METHOD
1. Verify that the leak is transmission fluid.
2. Thoroughly clean the suspected leak area.
3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
4. Park the vehicle over clean paper or cardboard.
5. Shut OFF the engine.
6. Look for fluid spots on the paper.
7. Make the necessary repairs.
POWDER METHOD
1. Thoroughly clean the suspected leak area with solvent.
2. Apply an aerosol type powder, such as foot powder, to the suspected leak area.
3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
4. Shut OFF the engine.
5. Inspect the suspected leak area.
6. Trace the leak path through the powder in order to find the source of the leak.
7. Make the necessary repairs.
DYE AND BLACK LIGHT METHOD
A fluid dye and black light kit is available from various tool manufacturers.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado
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