Truck Not Locking Into 4wd Hi

[jtkustomizer]

I am new to this forum and I am having problems with the 4wheel drive in my 1998 GMC Sierra Z71.

The truck is not going into 4wheel drive like it is supposed too. When I put the key in and turn the truck on the lights on the switch all turn on and then go off after about 5-10 seconds. I can push the 4wd hi button and the both lo and high lights go on and blink continually and the truck doesnt lock into 4wd. If I push the lo button it switches into lo just fine and everything locks in like normal. but getting it back into 4Hi or 2wd takes a couple of button pushes.

 

I took it to a dealership and they told me the switch in the dash was bad and that the actuator in the front differential was bad as well. My dad has the exact same truck and everything works just fine on it, so I switched the switch and actuator out of his and into mine and it still does the same stuff and his is works just like it is supposed to. This issue has baffled me for a while now and since it has started snowing/ getting Icy 4wd would be really nice to have again.

 

 

Thanks in advance.

[jtkustomizer]

Thanks Zaac Next time I go to my dads shop I will try switching these on the 2-trucks and see if that fixes the problem.

[zaac]

So you switched out the buttons and the front diff actuator; maybe you should switch out the TC encoder/actuator as well. I had to replace mine.

[DofD]

Hi there and welcome to GM Trucks!

 

The switch and actuator going bad are pretty common. But since you've eliminated those, hmm. Have you checked the wiring between the switch and actuator? Other than that, the better experienced here will need to chime in.

[jtkustomizer]

I havent checked the wiring but when I had the actuator out I had my dad push the buttons and the actuator actuates while it is out just like it should. By the way does the actuator have to be lined up in a specific direction once it is installed or should it just be tightened like any othe nut/bolt.

 

 

I also tried 3 different in dash switches and they all do the same exact thing. I will take pictures/ and or video of what it is doing later tonight.

[jtkustomizer]

So you switched out the buttons and the front diff actuator; maybe you should switch out the TC encoder/actuator as well. I had to replace mine.

 

 

Is this the one located on the transfer case. Does anybody have a picture of this?

[zaac]

So you switched out the buttons and the front diff actuator; maybe you should switch out the TC encoder/actuator as well. I had to replace mine.

 

 

Is this the one located on the transfer case. Does anybody have a picture of this?

 

Yes, it's on the front driver's side of the TC. You need to remove the front driveshaft, 2 electrical plug-ins and 3 bolts. 10 minute job. That's how it is on my 2000. I'm thinking '98 ain't much different.