4WD not working - doesn't do anything besides blink - 96 Yukon

[mstaake415]

Hi all!
I've got a 1996 GMC Yukon K1500 with the 5.7L Gas V8 and 4L60E Automatic transmission.

I recently bought it with about 114K miles. I didn't test the 4WD during the test drive because I didn't really care. But today I figured I'd try it out and well, it doesn't work. I read the owners manual so I'm not doing it wrong, but when I press the 4HI or 4LO buttons it just blinks and it never engages. I also have (though it's not currently in driveable condition, long story) a similar 98 truck with the same configuration and shortly after pressing the button you can feel it engage.

What troubleshooting steps should I take?

My Yukon also runs and idles pretty rough and the transmission slips a bit. Clearly not the most well maintained vehicle even though it has less miles than most of these. It might need an intake manifold gasket or a fuel spider, but that's not primary concern

 

[Nak]

There's a number of things that could cause this. Your best bet is to subscribe to AllDataDIY.com for your vehicle. That's basically the factory service manual on line. Look your issue up and follow the diagnostic steps.

 

[sgtpoliteness]

Alldata is great. Your 4WD issue sounds like it's probably the actuator in the front axle. My '96 tahoe I bought recently did the same thing.


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[mstaake415]

Hmmm... 4LO works but 4HI doesn't... Still the actuator?

 

[sgtpoliteness]

So 4Lo engages? The light stops blinking and you can feel it physically engage?

Does your output shaft to the front diff turn whole moving a little whilst trying to engage 4Hi?


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[bsamoul]

Mine has had the same problem since I got it. 4hi blinks. Replaced actuator, even replaced it with electric rather than thermal.

4lo physically does something, but the light still blinks.

 

[rabbiporkchop]

It's really cheap to convert it to a manual floor shift NP241. That's what I did when my ex wife's 99 quit engaging in 4wd.

 

[arctic388]

when mine did the same thing i replaced the dash switch with a used one from ebay and it works now.