1990 k1500 I from 4wd to 2wd the front axle stay's locked in. I have to take the actuator out wiggle the "pin" inside the differential to unlock it.

The spindle is what holds the front tires on. The axle is what holds the rear tires on. To remove the spindle, you have to remove the brake caliper first the remove the ball joint nuts. hit the spindle were the ball joints go in. The shock will release the ball joints. To remove the axles, you have to remove the differential plate, spin the differential until you see the bolt that locks the center pin in. remove both. push in the axle and remove the C clip. pull the axle out.

Torque Specifications

Description Nm lb-ft Axle-to-frame bolt 66 49 Axle damper-to-frame bolt 34 25 Brake caliper guide pin bolt 33 24 Differential bearing cap bolt 61 45 Differential housing cover bolt 29 21 Ring gear bolt 122 90 Tie-rod nut 91 67 U-joint spider retainer bolt 19 14 Upper ball joint pinch bolt 48 35

The Selectable Four Wheel Drive (S4WD) Front Axle consist of the following components:
• Differential Carrier Housing
• Differential Case Assembly
• Inner Axle Shaft
• Intermediate Shaft Bearing Assembly (located on the right side of the oil pan)
• Electric Motor Actuator
The front axle on Selectable Four Wheel Drive (S4WD) model vehicles uses a disconnect feature mounted on the right side of the oil pan in order to engage and disengage the front axle. When the driver engages the 4WD system, the Transfer Case Control Module sends a signal to the electric motor actuator to energize and extend the plunger inside. The extended plunger moves the clutch fork and clutch fork sleeve across from the clutch fork outer gear that is splined to the right side wheel drive shaft to the clutch fork inner gear that is splined to the inner axle shaft. The locking of the two gears allows the axle to operate in the same manner as a semi-floating rear axle. A propeller shaft connects the transfer case to the front axle. The differential carrier assembly uses a conventional ring and pinion gear set to transmit the driving force of the engine to the wheels. The open differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when going around corners and premature wear on internal axle parts. The ring and pinion set and the differential are contained within the carrier. The axle identification number is located on top of the differential carrier assembly or on a label on the bottom of the right half of differential carrier assembly. The wheel drive shafts are completely flexible assemblies consisting of inner and outer constant velocity CV joints protected by thermoplastic boots and connected by a wheel drive shaft.

How To Install Repair Replace 4x4 Front Axle Actuator Chevy Trailblazer...

no there is no auto locking hubs. 96 chevys have a ifs (independent front suspension) this give it more ground clearance but does not have lock out hubs, the cv axles go into the front differential an spin freely until you put it in 4wd, how this works is your transfercase spins the drive shaft that goes into the front differential an while you put it in 4wd it sends power to the actuator to lock the front differential. if your front end isnt pulling you either popped your 1 of your cv axles but if you did this you would know because it makes a very loud thunking noise while you're driving, my guess is you have a short thats not sending power to the actuator. check to see if the wiring harnesses are connected and check if the fuse that operates the 4wd in the cab of the truck is not blown. also actuators for these trucks are horrible they go out alot. also you can try reversing a few feet putting your truck in neutral an then try putting it in 4wd

when removing the front axle i believe that you must open the front differential cover and inside the dana you will see a small 8mm bolt located on the spider gear center it holds the pin bar in place and the pin bar holds both the upper and lower gears in place with a small washer below them. be careful when you pull the pin bar out to make sure the gears stay in place (upper and lower) do not let the washer fall out of the spider cage assembly. Then, carefully slide the U pin that holds the axle in (there are two of them one for the left axle and one for the right). Once the U pin slides off the axle the axle should slide all the way out of the whole differential - Note if the U pin you see at the end of the axle does not come off easy just push the axle IN ward towards the center of the differential and then slide it out with a small screw driver ..

4wd actuators are in the transfer case not the diff housing
on a diff housing it is more likely to be a diff lock to lock the 2 front wheels together

This would be a failing bearing in the differential. More specificly, I would suspect the pinion bearing. The differential will need to be disassembled and all (4) bearings and bearing races inspected for wear/ pitting.

On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED
INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Check the fuse to the 4x4, if the fuse is good then check the 4x4 electric motor actuator on the transfer case. You should hear it work from 2wd, 4hi to 4low and back to 2wd with the push of the switch. if you don't hear it working then check the wire harness at the actuator motor, look for any damages like corrosion or cracked wire connector clips. If the 4x4 actuator is working on the transfer case, then the front hub 4x4 actuator may have gone bad and that's located on the front differential. It's common for the clip there to corrode and break and is an easy fix with a new collar pin, at worst it's the diaphragm on the vacuum actuator that is located under the battery tray. There is a vacuum switch on the top of the transfer case, driver side but when that fails, your front hub stay's locked in the on position. Good luck and keep me posted and hope it's a simple fuse that has gone bad. You can pick up all these parts at Auto Zone or Parts Source and they will have the step by step instructions for you to get the job done with common tools.

there is a vacuum actuator under the battery it could be leaking vacuum. There is also an electric actuator on some models found in the same place. There is a cable that runs from the actuator to the front differential that locks it in. Make sure you have vacuum and the actuator is pulling the cable when 4x4 is engaged. hope this info helps.