4 Wheel Drive/SUVs: 96 chevy 1500 four wheel drive wont engage, differential assembly, chevy 1500

Question
I have a 1996 Chevy truck and the four wheel drive will not work changed the acutuator and checked voltage was 11.9 I jacked the truck up put in four wheel drive the front drive shaft turns but still no power to the front wheels took  a screw driver and tried to push the front end sleeve in to engage it with still no sucess do you have any ideas

Answer
James,
Here is a copy of a bulletin about this problem.

1996 Chevy Truck K 1500 Truck 4WD VIN W
Transmission and Drivetrain  Differential Assembly  Actuator  Technical Service Bulletin.  Drivetrain - Slow Or No Engagement of Front Axle

File In Section: 4 Drive Axle
Bulletin No.: 76-43-01A
Date: September, 1998

Subject:
Slow or no Engagement of Front Axle when 4WD is selected (Replace Front Axle Actuator)

Models:
1988-97 Chevrolet and GMC K Models
excluding 1988-93 Models over 8500 # GVW

This bulletin is being revised to add information to the Service Procedure, add a new part number, and include schematics. Please discard Corporate Bulletin Number 76-43-01 (Section 4 - Drive Axle).

Condition

Some owners may comment that the colder the outside temperature is, the longer it takes for the front axle to engage when 4 wheel drive is selected, or the front axle does not engage.

Cause

The front axle engagement actuator is a thermally activated component. Because of this characteristic, the time required for the actuator to complete 4 wheel drive engagement is extended as the temperature drops.

Correction

Replace the front axle actuator and include the applicable wiring harness kit. Refer to the Parts Information in order to determine which wiring harness kit is needed.

1996 model trucks with a build date on or after January 2, 1996 are considered as "961". If the build date of the truck is unknown, verify the 3 character "axle code" on the front axle label in order to determine which wire harness to order.

This new actuator uses a motor to engage the front axle and is not affected by temperature. On 1988-93 models with a GVW rating over 8500$, the new actuator cannot be installed and the thermal actuator will remain the service part.

Parts Information

P/N          Description          Qty

26060073        Actuator Asm, Frt Drive Axle     1
22510339        Fastener          1
15313272        Harness, Jumper (Z Splice)       1
         (86-93 K1-3)

Parts are currently available from GMSPO.

Warranty Information

Some owners with actuators that are operating as designed (5-30 seconds engagement time) may choose to upgrade to the fast actuator at their own expense. The fast actuator is a new product enhancement and should not be used to replace actuators that are operating as designed.

Hope that this helps,

Carl