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Matt J, Chevy Technician
Category: Chevy
Satisfied Customers: 1399
Experience:  10+ years automotive tech, 5 years of experience in a GM dealer
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Chevy 1500 four wheel drive is not working. Please help!

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Is the transfer case engaging?

Customer: replied 7 years ago.

It is engaging. When I took the drive shaft out, i had my daughter engage and disengage, so I could turn the driveshaft to access the bolts on the retainers. Then I could get the driveshaft out. It would not turn while it was engaged. So I am assuming it is engaging. The light on the floor shifter is not working, is that telling me no electricity is going to case?

Usually that means there is no electricity to the actuator. GMhad a harness update to the front actuator... I would start by calling Chevy and getting the harness update

File In Section: 4 Drive Axle

Bulletin No.: 76-43-01A

Date: September, 1998

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


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 four - Drive Axle).


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


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


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.

For vehicles repaired under warranty, use:

Customer: replied 7 years ago.

I put in a brand new actuator again this year, thinking it was the problem and still nothing worked. It has been in my garage for three days at 50+ degrees. Seems to not be getting any electricity to do the job. Solenoids or something? the light on the shifter doesn’t work, either when selecting 4h or 4l and it did till this started to happen.

If the transfer case is engaging, it’s in the wires to the front actuator.


Customer: replied 7 years ago.

Ok, so out of all the diagrams i see to replace case switch, where is it and do you think that is the problem? I am sorry to be so stubborn, but it just seems it should be kind of simple. Worked fine last year.....

  1. Disconnect battery ground cable, then remove console and slide shift boot up selector lever.
  2. Disconnect switch harness at indicator assembly, then remove clip and switch.
  3. Position new switch on mounting bracket and install attaching screw. Ensure shift lever assembly pawl is on switch contact carrier.
  4. Route wiring as shown.
  5. Install shift boot, console wiring harness and console, then connect battery ground cable
  6. graphicgraphic
Customer: replied 7 years ago.

Neither of the diagram is for my truck. I took console off and found wires coming up from under the floor to the lights / indicator, and that was it, no switch or electricity of any kind!! Any other options?

Thats what my data shows, I’ll opt out, see if anyone else has a better idea....I still thinks it’s a faulty actuator issue, if the transfer case engages.

Customer: replied 7 years ago.

I replaced the actuator with a brand new one this year thinking the same thing, but nothing worked. Is fluid an issue which I need to check / change the fluid? What are the fuses, relays? Am I checking the right fuse? Marked t case 20A.

Hello, Welcome to JustAnswer!

I will be more than happy to assist you.

If you will disconnect the front drive shaft from the transfer case and leave it connected to the front diff, engage the 4X4 and try to turn the drive shaft by hand. Does the drive shaft still turn, with it connected to the front diff?

Customer: replied 7 years ago.

I have the driveline out, getting the u joints replaced. When i try that, what am i looking for? What should or should not happen? Could I have a bad new actuator . So I think it is not an electric problem? I want to change the actuator but kind of spendy....

This test verifies if the front diff actuator is or is not engaging. I want to make sure and not over look anything.
Customer: replied 7 years ago.

Ok, I am working today and will do it tonight. How do i get back to you, so we can continue with this? Now when i do the drive line test, should the truck be in the on position (not running), because the actuator has to heat up right? So turn the driveline by hand, if it turns what then? If it does not turn then what?

One thing I do need to know, does the front diff actuator have 2 wires that plug it to the actuator, or does it have a cable going to it.

All test should be done with the vehicle running and in 4X4.

If the shaft does turn then the front diff actuator is not working.

If it does not turn then try to turn the transfer case output yoke that connects to the front drive shaft by hand. If it does not turn then 4X4 should be working. If it does turn then let me know and we will go from there.

Customer: replied 7 years ago.

It is a wire connector with two wires coming out of the plug. This is weird because it seems to be electrical, not mechanical. I will try this stuff tonight and get back to you tomorrow. I would have thought, this would have been something real obvious that i was just overlooking electrically. case switch under console?? I looked there but, there were only two wires coming up from under floor to connect to the two lights for indication of being in four-wheel drive, which are not lighting up!!

When you shift it into 4X4, are the 4X4 lights lighting up?

Customer: replied 7 years ago.

No, not at all, seems to be getting no electric to the console at all.

I missed that info when I was looking over everything that had been done.

That changes things so at this time disregard the test I wanted you to do.

Do you have a test light?

Customer: replied 7 years ago.

Your problem should be the Transfer Case Switch. Look on the Transfer Case for a switch that has 3 wires that go to it. Light Blue, Dark Blue, and Brown.

Unplug the connector, take 3 pieces of wire, and insert them in the wire connector slots. Then twist the wires together so all 3 wires are hooked to each other. Now see if the 4X4 works. If it does, then the switch is bad.

The switch cost about $15.


Customer: replied 7 years ago.

I took that off and it looked like nothing but a sensor. It seemed to only have two wires. Maybe i got the wrong thing off. This was on the side of t case and it looked like it was in fluid. Now that i have the drive line out, I can probably get to it. It is on top of case?? This is what feeds the actuator and the lights on the console?? I really appreciate your patience with me, this is just so frustrating.

I also meant to add in, make sure the GAUGES 10 Amp fuse is no blown.

What really make this difficult on my end is, there are 3 transfer cases and 3 wiring diagrams. None of them tell me which is which, and I can’t see your vehicle to verify which transfer case is in it. I know it is not the auto push button, since you stated you have a shifter to on the left side

This sensor will be right next to the front drive shaft on the Transfer Case.

Customer: replied 7 years ago.

Thanks alot!! I think we are on to something.... I will let you know what happens tomorrow!! So this is on top of t case not on the side. I have looked at all fuses and relays and have found nothing blown. Does this switch go out often? No one ever suggested this!!!

If the sensor is there and has 3 wires going to it, then yes that should be the problem.

The sensor allows power to go to the actuator and the bulbs when it is shifted into 4X4.

No one suggested it because, they went looking at the correct wire diagram.

Customer: replied 7 years ago.

Since you have been a help for me, how will i let you know personally, what exactly the problem is?

Just reply back to this post once you find out.
Customer: replied 7 years ago.

Ok, thanks again for putting up with me. I always suggest to my friends to ask you guys before diving into anything. Your awesome!!

Ok, tried the switch and still nothing, please help.


Go to the switch, which I have asked you to look at, with the key in the on position, check and see if you have power at the Brown wire.

Customer: replied 7 years ago.

I will check it out If power is there, then what? If no power then what?

If no power then check the 4WD fuse, see if the fuse is blown and also test to see if you have power there. If you have power there, then you have an open in the wire. If no power then let me know,I will trace down the power source. Make sure these tests are done with the key on.

If there is power and the switch is good then you have an open in the Light Blue wire or an internal problem inside the transfer case.

Matt J, Chevy Technician
Category: Chevy
Satisfied Customers: 1399
Experience: 10+ years automotive tech, 5 years of experience in a GM dealer
Matt J and other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Ok, I have changed the front diff switch, the front actuator, the transfer case switch and still nothing. I have the vehicle on jack stands and when I engage 4wd the front drive shaft turns fine, just no front axle engagement. I am getting no electricity to the console or the actuator. On my fuse box, there is a number 2 slot for the case fuse but there is nothing in the slot to put a fuse into. Could it have gotten knocked out somehow? I am thinking this may be my problem!! Can you show me a wire diagram for this vehicle, so I can see what the fuse box shows for 4wd fuses, at this time I only have 2 fuses to check, 14 and 24.

Fuse #24 is the fuse .This fuse should have power when the key is in the ON position. Here is the Fuse block lay out and wire diagram.



Matt J, Chevy Technician
Category: Chevy
Satisfied Customers: 1399
Experience: 10+ years automotive tech, 5 years of experience in a GM dealer
Matt J and other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Matt I have power there at the 24 fuse. With key in on position, not running. I tested the 14 fuse and the test light barely lit up, very dim, hardly on. Is the new wiring harness going to cure this? I have power at the actuator fuse but then what?

Customer: replied 7 years ago.
was anyone able to respond to my reply??

Sorry for the delay, I am in the middle of rebuilding a Trans in a Cadilliac.

Do you have a voltmeter?

Customer: replied 7 years ago.

No, could the new wiring harness fix all this? I am confused as to how can there be power to the actuator fuse and then nowhere else. The drive shaft turns great when in 4wd, but no actuator action. New wiring harness?

Go to the Transfer Case switch, unplug it, put the vehicle in 4X4 and test the Brown wire for power with the test light. Does the test light, light up? (All Test Should Be Done With the Key ON and In 4X4.)

If yes, then plug it back and probe the Light Blue wire. Does the test light,light up?

If yes, then plug it to the front diff actuator, leave the vehicle in 4X4 and test the Light Blue wire for power. Does the test light, light up?

Customer: replied 7 years ago.

Ok, I’ll try all this. What ifI have a bad new transfer case switch? You referred once to a transfer case sensor. Is that the same as the switch??

Yes, it is the same switch. Now that the switch did not fix it like I thought,we need to do some test to find out where power is getting too. I don't think the new switch is bad, but it can happen.

Do the test and let me know if you have power at all these places. If you do, then we will move to the next steps.

Customer: replied 7 years ago.

Ok. Thanks for being patient with me. I know I can fix this problem. I just do not understand why all of a sudden this year the 4wd does notwork. I may bebe getting close. The new wiring harness is $300 and I do not have that amount now to replace it. I don’t think that is the problem.

No problem. I will be here for you until we find the cause. There is no reason to get a $300 wire harness, since we do not know the cause yet. There are only 3 parts, it could be or an open in the wires. With these tests, we will get closer to the cause.

Customer: replied 7 years ago.

ok I tried your 3 wire insert test into plug. The console lit the heck up. Light blue wire has no power at switch, brown wire has power!! Man Im feeling good now... so now what??

Leave the Transfer Case switch plugged in and put it in 4X4.

Go to front diff actuator, unplug the connector and test the Light Blue wire for power. Does the test light, light up?

Customer: replied 7 years ago.

The light blue wire has no power.

The Blue Wire at the Actuator on the Front Diff has no power?
Customer: replied 7 years ago.

There is no power in the blue wire on the front diff.

Go back to the Transfer Case Switch, leave it plugged in with the vehicle in 4X4, and the problem is in the Light Blue wire, does it have power at the Transfer Case Switch?

Customer: replied 7 years ago.

Matt I got it!!!! You won’t believe this, there was a rubber o ring on the transfer switch. Took it off, reinstalled the switch and voila!!!!!!!! Thanks for your help!!!!! If it wasn’t for the wiring test, I would not have known the light blue wire had no power, so it had to be something with the switch. Thank you

Great, you found the problem. I knew it had to be in that area, since things were not adding up after the switch.

Matt J, Chevy Technician
Category: Chevy
Satisfied Customers: 1399
Experience: 10+ years automotive tech, 5 years of experience in a GM dealer
Matt J and other Chevy Specialists are ready to help you