4wd Problems- Won't engage

[etiger]

Alright, my 4wd switch has been acting weird; it will randomly light up 4wd H and then even go into Neutral although it doesn't actually change into any of those. It will just happen as I am driving down the road. Alot of times the service 4wd light will come on.

So I was driving home today and I noticed that it had put me in 4wd Auto. So I hit the 2wd light and it switched it back. A few miles down the road it turned it into neutral. The light did not change, but it actually put the car in neutral (i.e. when I hit the gas it just reves the engine). I pulled over and tried to put the car in park but it stayed in neutral and the car starts rolling. So I hit the auto button and everything was ok. So I went and bought a new 4wd switch since I heard that a bunch of people have had issues with the light not working. So I switch it out and it is still acting up. Now, unless I leave the car in 4wd auto it will kick the trans into neutral. Also, if I try to change into 4wd L it makes 2 or three very loud clicking sounds and will not go into it.

I have heard that it may be the actuator...just trying to confirm before I spend the money.

Any ideas???? Please help.

[777stickman]

Wow, pretty wierd deal you got there. Couple of ?'s for you. I'm assuming since this post is in the Tahoe forum that you've got a Tahoe, but beyond that We need to know year and engine. Things change so much from year to year that ????????????? who knows. I have a '98 K2500 Sub with the push button auto 4wd system. I chased a t-case fuse blowing for 4 months. Changed the encoder motor and the control module and then found a short in the power wire.

So back to your trouble. You've changed the switch which has been a big problem over the years. Good job, but it didn't help. You're still getting uncommanded t-case changes, not good.

Here's how my '98 works. You push a switch, that sends a signal to the t-case control module that sends a signal to the encoder motor on the t-case to change gears. Been sitting here for 20 min's trying to figure out how to trouble shoot your problem. So, here's the deal. You need to get your Tahoe?? scanned with a good tool (Snap-On) to see if there are any DTC's for the 4wd system and let us know what they are, if any.

Post back..................Steve

[etiger]

Sorry, it is a 2004 Tahoe Z71, 5.3L engine. I will take it by someplace to have the codes read. Do you think it may be the actuator? I have read a bunch of postings saying that this part is also a problem.

Thanks for the help.

Eric

[777stickman]

Eric: The actuator in my '98 has an internal braking system that prevents the t-case from shifting itself without a signal, supposedly. If that braking system failed, could the t-case shift itself?? I don't know. Maybe someone else can jump in here and help out as I'm just not that familiar with the newer models. If my '98 was doing this and I could prove somehow that it wasn't getting a random electrical signal, the actuator would be my 1st choice......Steve

[etiger]

Can anyone else help me!!? Please