Auto4WD not working properly...?

[derekjl]

Now that the snow is falling again I am started to use 4WD in my 1999 Tahoe. I noticed this last winter as well, but the Auto4WD function doesn't seem to be working properly. There are no service lights or anything on the dash. Basically this is what happens. If the truck is shifted from 2HI to Auto4WD, the 4WD will engage when loosing traction. HOWEVER, the truck will not return to 2HI by itself, you have to manually push the 2HI button. I know this because you can still hear and feel the front axles engaged. This gets annoying when going from pavement to slick surfaces many times during a drive. Anything I should have looked at first? I have Auto Trac II in the transfer case. I made sure of this over the summer.

 

[99Vortec]

As I understand it, there's an Encoder motor located in the transfer case.

A Front axle actuator.

And the 4x4 dash mounted selector switch.

Personaly, I don't use Auto 4WD much as it seems to "Hit" too hard when it engages/disengages.

I would first check for damaged wiring leading to the front actuator.

Tricky though. Good luck!

 

[derekjl]

Thank you. Looks like that encoder motor is pretty expensive. I should also add that I couldn't get the transfer case into neutral as per the manual. At least the red indicator light wasn't coming on...?


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[99Vortec]

That's what's tricky about it. If the indicator light was on, it might help to lead to the defective component.

 

[derekjl]

I wonder if the previous owner realized this and just said forget it. What sucks is that my tires aren't good enough in snow to leave it in 2HI all the time but leaving it in 4HI all the time isn't necessary, especially on dry pavement which I've heard is a no no.


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[99Vortec]

Yea, leaving it in 4wd on dry pavement will definitely damage the transfer case.

*Edit* Here's a case study where a guy diagnoses a GM transfer case/4wd problem.

http://www.motor.com/article.asp?article_ID=796