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Well, driving to work this morning I put the truck in 4wd. I do this occasionally to engage the system (I only do it on long straightaways). Anyways, the truck shifted into 4WD and the "service 4wd" light immediately came on. Now it won't shift back into 2WD. I know it is in 4WD as I can hear the drivetrain noise that I normally hear and making turns into the parking lot were alot of fun (I know this is bad but I had no option). When I finally got out of the truck - I pushed the 2WD button again and I could hear a mechanical noise from underneath the truck like it was trying to shift into 2wd. It attempted twice, and the the light on the 4wd button came back on and it stopped trying.

 

Anybody out there with an idea what this could be? I know several people on here have had the 4WD switch problems - do these symptoms align with that specific problem? I am somewhat comforted by the fact that the 4WD still works - it makes me think that this is not a transfer case problem. I just wonder what that mechanical mechanisim (sp?) is that moves the truck from 2WD to 4WD - maybe that broke?

 

Last week the alternator took a dump...now this. Those '09 model trucks are looking nicer each day, although mine being paid for is nice too! HELP!! :D:cool:

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I had a 99 Chevrolet Z-71 years ago and I had the same identical symptom. A buddy of mine had the same symptom too and it was the switch.

 

If I recall I removed the dash, unscrewed the screws holding in the switch and replaced the switch and that fixed it.

 

 

Well, driving to work this morning I put the truck in 4wd. I do this occasionally to engage the system (I only do it on long straightaways). Anyways, the truck shifted into 4WD and the "service 4wd" light immediately came on. Now it won't shift back into 2WD. I know it is in 4WD as I can hear the drivetrain noise that I normally hear and making turns into the parking lot were alot of fun (I know this is bad but I had no option). When I finally got out of the truck - I pushed the 2WD button again and I could hear a mechanical noise from underneath the truck like it was trying to shift into 2wd. It attempted twice, and the the light on the 4wd button came back on and it stopped trying.

 

Anybody out there with an idea what this could be? I know several people on here have had the 4WD switch problems - do these symptoms align with that specific problem? I am somewhat comforted by the fact that the 4WD still works - it makes me think that this is not a transfer case problem. I just wonder what that mechanical mechanisim (sp?) is that moves the truck from 2WD to 4WD - maybe that broke?

 

Last week the alternator took a dump...now this. Those '09 model trucks are looking nicer each day, although mine being paid for is nice too! HELP!! :D:cool:

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I'd go with the switch.

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dumb question...I have never had a Z71/4x4 personally but does this happen more frequently with the push button 4x4 or the floor shifter 4x4s?

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As I recall, the switch for the automatic transfer case has been a problem over the years. I believe that the switch is the same for any of the Chev/GMC/Caddy vehicles with the auto-trac system.

 

I had to replace the switch on my 99 Z71 a few years ago. I kept getting a Service 4WD message and the switch would not allow engaging any of the selections. Fortunately, the replacement take all of 5-6 minutes to do. Remove the trim around the dash by pulling gently and the screws are at the top and bottom of the switch.

 

Once you get the DIC message, the switch should have no function. But I never had an occurrence of being in 4WD and not being able to get out of that setting when the DIC message showed up. :D But shutting off the ignition switch and then turning it back on usually would reset the DIC and the switch would work again for awhile/

 

I paid just over $50 for the switch I bought but like anything else, prices have gone up. I think they can be found for cheaper than the dealer on places like GMPartsdirect, GM Partshouse or even eBay.

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It seems that the most common cause of this sort of problem is the pushbutton module itself - so I am going with the autotrac system. It's kinda funny...the autotrac system is more expensive to begin with and gives us probems and costs us money down the road. Maybe we should go with the floor lever next time...

 

I am going to replace the switch during lunch - there is a dealership down the road and they have the part in stock. I have also read about other common causes such as the "transfer case control module" and the "encoder motor / sensor". Not sure what those do and they sound expensive...let's hope it is the switch. I will post after lunch.

 

Oh...the truck is stuck in 4WD. I have to drive it up the road...am I going to do any real harm? I won't make any sharp turns or anything...

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I had the same problem once this winter with mine. I put it in 4 low to pull buddy out of the ditch and had a biatch of a time getting it to go back to 2wd, could here it trying and the light would flash then it would go back into 4 low, finally went back to 2wd after a while. Have used it a couple time since and it has worked fine, i figured it must have been something in the switch to.

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On my 1999 GMT 800, the fuse blew on the shift circuit once. I replaced it and it has been fine for a couple yrs now.

 

Check your 4wd fuse which is located in the fuse panel on the side of the dash when you open the door (not the panel under the hood). I'm not saying that's it, but it takes little time to check it before spending money.

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Well, I drove to the dealership (still in 4WD). Bought the swtich ($81 out the door...ouch) and installed it. It didn't fix it...and to add salt to the wound I couldn't return the switch (I knew that before I bought it...).

 

I am really in a bad spot since the truck is stuck in 4WD. I can't drive it around like that so I just left it with the dealer and am mentally preparing myself for what is to come. What else could I do? Have it towed somewhere? I also figure that the dealer has dealt with this specific problem whereas a local shop would be guessing as to what the problem is.

 

Since the 4WD works I am pretty confident that it is something electrical - probably like an actuator or something. Thoughts?

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My dad 99 jimmy did the same thing. When you pushed the button you could tell it was trying to switch back into 2 wheel drive but it would shift back. We took it to a tranny shop and it turned out to be the 4 wheel drive shit motor. They took all apart and but it back in but the motor had to be replace.

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drive strate line then stop and put it on reverse drive in reverse for 20-40 yards and it will disengage

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drive strate line then stop and put it on reverse drive in reverse for 20-40 yards and it will disengage

 

That should work, I think that is stated in the manual as well. Also when trying to switch from 4 lo to 2 hi you should be rolling forward with the trans in neutral.

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