Chevrolet Silverado / GMC Sierra. Service manual — part 2839

TRANSFER CASE WILL NOT SHIFT

Refer to Transfer Case Disassemble and Transfer Case
Assemble.

High/low internal gear

1. Inspect the high/low internal gear to front case fit for

excessive looseness.

2. Replace the front case half if the high/low internal gear is

loose. Refer to Transfer Case Disassemble and
Transfer Case Assemble.

High/low clutch

1. Inspect the high/low clutch engagement teeth for

excessive wear.

2. Inspect the high/low clutch to rear output shaft splines for

excessive wear.

3. Replace the high/low clutch if faulty. Refer to Transfer

Case Disassemble and Transfer Case Assemble.

Cause

Correction

DEFINITION: While shifting from HI range to LO range, there is gear clashing or no HI
range. Or the transfer case will not shift from 2 wheel drive to 4 wheel drive.
Review the Symptoms - Transfer Case and perform the necessary inspections.

Shift linkage worn

1. Inspect the shift linkage for correct adjustment or for

being worn.

2. Replace the faulty component. Refer to Transfer Case

Control Lever Replacement and Transfer Case
Control Rod Replacement.

Mode shift clash

1. Disassemble the transfer case. Refer to Transfer Case

Disassemble.

2. Inspect the synchronizer for being faulty. Refer to

Two/Four Wheel Drive Shift Components Cleaning
and Inspection.

3. Replace the synchronizer if faulty. Refer to Transfer

Case Assemble.

1. Disassemble the transfer case. Refer to Transfer Case

Disassemble.

2. Inspect the synchronizer sleeve for sliding freely on the

synchronizer hub.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Mode block

3. Inspect the synchronizer sleeve or synchronizer hub for

being faulty.

4. Replace the synchronizer sleeve or synchronizer hub if it

is faulty. Refer to Transfer Case Assemble.

If the symptoms occur during cold temperatures, flush and fill
the front axle with synthetic fluid. Refer to Front Axle
Lubricant Level Inspection (9.25 Inch Axle) .

High/low shift fork

1. Inspect the high/low shift fork for the following

conditions:

The pin on the shift fork for wear or damage

Worn or melted range fork pads

Cracked or bent shift fork

Refer to High/Low Shift Components Cleaning
and Inspection .

2. Replace the following components if found faulty:

The shift fork pads

The shift fork

Refer to Transfer Case Disassemble and
Transfer Case Assemble .

High/low clutch

1. Inspect the high/low clutch for the following conditions:

Engagement teeth for burrs or damage

Sliding freely on the rear output shaft

The high/low clutch collar for excessive wear

Refer to High/Low Shift Components Cleaning
and Inspection .

2. Replace the high/low clutch if faulty. Refer to Transfer

Case Disassemble and Transfer Case Assemble.

1. Inspect for the following conditions:

Failed input shaft pilot bearing in the input shaft

Journal on the rear output shaft for excessive wear

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

TRANSFER CASE JUMPS OUT OF GEAR

Input shaft pilot bearing
assembly

or damage

Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection and Rear Output Shaft
Cleaning and Inspection .

2. Replace the bearing if faulty. Refer to Input Shaft Pilot

Bearing Replacement (Light Duty) or Input Shaft
Pilot Bearing Replacement (Heavy Duty and Super
Heavy Duty).

3. Replace the rear output shaft if damaged. Refer to

Transfer Case Disassemble and Transfer Case
Assemble.

High/low planetary carrier
assembly

1. Inspect the high/low planetary engagement teeth for burrs

or damage. Refer to High/Low Planetary Carrier
Cleaning and Inspection.

2. Replace the high/low planetary carrier assembly if faulty.

Refer to Transfer Case Disassemble and Transfer
Case Assemble.

Cause

Correction

DEFINITION: Loss of the transfer case drive torque during deceleration, acceleration or
under load.
Review the Symptoms - Transfer Case and perform the necessary inspections.

Shift linkage worn

1. Inspect the shift linkage for correct adjustment or for

being worn.

2. Replace the faulty component. Refer to Transfer Case

Control Lever Replacement and Transfer Case
Control Rod Replacement.

High/low shift fork pads

1. Inspect the high/low shift fork pads for wear. Refer to

High/Low Shift Components Cleaning and
Inspection.

2. Replace the fork pads if worn. Refer to Transfer Case

Disassemble and Transfer Case Assemble.

1. Inspect the high/low shift fork for being damaged. Refer

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Faulty high/low shift fork

to High/Low Shift Components Cleaning and
Inspection.

2. Replace the shift fork if faulty. Refer to Transfer Case

Disassemble and Transfer Case Assemble.

Faulty high speed teeth on
the high/low clutch

1. Inspect for the following conditions:

The input shaft high speed engagement teeth for
wear or damage

The engagement teeth on the high/low clutch for
wear or damage

Refer to Front Output Shaft and Input Shaft
Cleaning and Inspection and High/Low Shift
Components Cleaning and Inspection .

2. Replace the high/low clutch if the teeth are faulty. Refer

to Transfer Case Disassemble and Transfer Case
Assemble.

3. Replace the input shaft if the engagement teeth are faulty.

Refer to Transfer Case Disassemble and Transfer
Case Assemble.

Faulty control actuator shaft

1. Inspect the control actuator shaft for wear. Refer to

High/Low Shift Components Cleaning and
Inspection.

2. Replace the control actuator shaft if faulty. Refer to

Transfer Case Disassemble and Transfer Case
Assemble.

High/low planetary carrier
assembly

1. Inspect the high/low planetary carrier for the following

conditions:

Low speed engagement teeth worn or damaged

Cracked carrier housing

Planetary gear needle bearings worn

Planetary gears broken or damaged teeth

Planetary gears seized or binding

Refer to High/Low Planetary Carrier Cleaning
and Inspection .

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - MP 1222/1225/1226-NQG - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado