Chevrolet Silverado / GMC Sierra. Service manual — part 740

5. With the engine at idle speed and the transmission in PARK or NEUTRAL, observe the

vibration. Refer to Noise and Vibration Analysis .

Repeat this procedure until you obtain the best possible balance.

6. Install the transmission converter cover bolts and the cover.

BUSHING AND MATING SHAFT INSPECTION

Any of the following bushing conditions require replacement of the bushing and/or housing:

Discoloration due to heat distress

Misalignment or displacement of bushing as a result of spinning in housing

Medium to heavy scoring that can be easily detected with fingernail. Light scoring is a
normal condition.

Debris embedded into the bushing lining material

Obvious damage, including excessive and uneven wear

Excessive polishing. Minor polishing of the bushing is an indication of normal wear and
does not require replacement.

Any of the following conditions require replacement of the bushing's mating shaft:

Discoloration due to heat distress

Rough surface finish that can be easily detected with finger

Obvious shaft abnormalities, including warping or uneven surfaces

Obvious damage or cracking

VIBRATION

IMPORTANT: Proper bushing and corresponding mating shaft inspection

should be performed before replacing the bushing, shaft, and in
some cases, the component which houses the bushing.
Thoroughly clean and dry the bushing and shaft surfaces before
inspecting for damage.

Checks

Causes

Lug bolts for the Torque
Converter (1)

Inspect for loose torque converter (1) lug bolts.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

NOISE AND VIBRATION ANALYSIS

A noise or vibration that is noticeable when the vehicle is in motion MAY NOT be the result of
the transmission.

If noise or vibration is noticeable in PARK and NEUTRAL with the engine at idle, but is less
noticeable as RPM increases, the cause may be from poor engine performance.

Vibration may also be caused by a small amount of water inside the converter.

Inspect the tires for the following conditions:

Uneven wear

Imbalance

Mixed sizes

Mixed radial and bias ply

Inspect the suspension components for the following conditions:

Input Sun Gear Thrust Washer
(55)

Inspect for wear or damage.

Turbine Shaft Thrust Bearing
Assembly (57)

Inspect for wear or damage.

2-6 and 3-5-R Clutch Hub
Thrust Bearing Assembly (65)

Inspect the bearing for wear or damage.

Output Carrier Assembly (68)

Inspect the carrier assembly for damaged pinion
gears, thrush washers, pins, and rollers.

Inspect for a worn or damaged center support roller
bearing assembly (485).

Inspect for damaged thrust bearings (486, 488).

Inspect the carrier assembly for damaged output
carrier rear sun gear thrust bearing (captured).

Output Carrier Thrust Bearing
Assembly (69)

Inspect the bearing for wear or damage.

Output Shaft Thrust Bearing
Assembly (71)

Inspect the bearing for wear or damage.

1-2-3-4 Clutch Hub Thrust
Bearing Assembly (63)

Inspect the bearing for wear or damage.

Turbine Shaft Thrust Bearing
Assembly (57)

Inspect the bearing for wear or damage.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Alignment wear or damage

Loose fasteners

Driveline damage or wear

Inspect the engine and transmission mounts for damage and loose bolts.

Inspect the transmission case mounting holes for the following conditions:

Missing bolts, nuts, and studs

Stripped threads

Cracks

Inspect the flywheel for the following conditions:

Missing or loose bolts

Cracks

Imbalance

Inspect the torque converter for the following conditions:

Missing or loose bolts or lugs

Missing or loose balance weights

Imbalance caused by heat distortion or fluid contamination

WHINE/GROWL NOISE THAT CHANGES WITH VEHICLE SPEED

Checks

Causes

2-6 and 3-5-R Clutch Hub
Thrust Bearing Assembly (65)

Inspect the bearing for wear or damage.

Output Carrier Assembly (68)

Inspect the carrier assembly for damaged pinion
gears, thrust washers, pins, and rollers.

Inspect for a damaged center support roller bearing
assembly (485).

Inspect for damaged thrust bearings (486, 488).

Inspect for damaged sun gears (487, 489).

Inspect the carrier assembly for damaged output
carrier rear sun gear thrust bearing (captured).

Inspect for damaged or stripped splines on the output
carrier assembly.

Output Carrier Thrust Bearing
Assembly (69)

Inspect the bearing for wear or damage.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

NOISE IN FIRST OR REVERSE GEAR

Output Shaft Assembly (70)

Inspect for damaged internal gears (495, 497).

Inspect the output carrier bushing (498) for damage
or wear.

Output Shaft Thrust Bearing
Assembly (71)

Inspect the bearing for wear or damage.

Input Sun Gear Thrust Washer
(55)

Inspect the washer for wear or damage.

Input Sun Gear Thrust Bearing
(54)

Inspect the bearing for wear or damage.

Input Sun Gear (53)

Inspect for spline wear or damage.

Input Carrier Assembly (52)

Inspect the carrier assembly for damaged pinion gears,
thrust washers, pins, and rollers.

1-2-3-4 Clutch Hub Thrust
Bearing Assembly (63)

Inspect the bearing for wear or damage.

2-6 and 3-5-R Clutch (with
Output Carrier Outer Sun Gear
Shaft) Hub Assembly (64)

Inspect the output carrier inner sun gear shaft bushings (60
and 62) for damage or wear.

Turbine Shaft Thrust Bearing
Assembly (57)

Inspect the bearing for wear or damage.

Fluid Filter Assembly (26)

Inspect for damaged or restricted fluid filter assembly
(26)

Inspect for damaged fluid filter seal assembly (25) or
improper sealing interface (leaks, fluid aeration).

Automatic Transmission Fluid
Pump Seal (5)

Inspect for worn or damaged seal.

Checks

Causes

Center Support with 2-6 Low
and Reverse Clutch Assembly
(67)

Inspect for damaged or worn low and reverse clutch
plates (463-465).

Inspect for damaged low and reverse clutch backing
plate (462). Inspect for worn splines on backing
plate.

Inspect for damaged low and reverse clutch backing
plate retaining ring (461).

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado