Lost 4wd in my 08 duramax today

When I got off work today it was misting rain and 25 degrees. On the way to pick the granddaughter up from school the roads became a mess of black ice. The truck was like a pig on ice. I had to put it in 4wd just to take off from a stop light. A short while later a car slid through a stop sign and I went into maybe a 30ft slide doing my best not to T-bone her. I could feel the anti lock brakes pulsating and it did get me stopped although I was facing north and needed to go west. I turned the wheel sharp to straighten up and it kind of crab walked a little with me and seconds later I got a message that said service the 4wd. I could tell by the way that I was able to take off that it was still in 4 wheel. When I got off the main road and on my gravel drive I stopped and put the truck in neutral. It has the knob on the dash and I turned it to two wheel and I could not tell if it came out of 4wd or not. The lights on the knob did nothing. I then tried to select N or 4 wd low and it would do neither. What do I need to check and where do I go from here. The truck still drives in what I think is 2 wheel drive hi at this time. It is still icing outside and I don't have a clue if it will work for me in the morning or not. My old 86 Chevy I had for years would go about anywhere in 2 wheel. Not so with this 08 Duramax, It spins like Oprah on a banana peal on a slick surface. I have had to use 4wd on wet grass with this truck. Thank for any advice.
Paul

With mine, you had to be slightly moving to engage or disengage 4wd High.

I really meant to type at least slighty moving.

Try backing up some when coming out of 4wd. It takes the 'binding' out of the driveline, at least on the older stuff. Duramax may have a power divider in the transfer case to prevent that.

Garry

And look at the fuses.

I tried going forward and back and it seemed to make no difference. I have not checked any fuses yet though. I may have to dig into my book for a while to figure out which fuse it may be.

Find someone with a diagnostic scanner and see what is in the computer. Other wise you end up throwing parts at it.

A lot of vehicles and makes use the same transfer case. Just different bolt ons. You might have a stuck shift motor that puts it in 2-4-and 4 low. It is even more fun when the drive chain inside lets go. Had three cases over several years. Different vehicles.

Our 2002 Trailblazer has since shucked the front axle, so no 4x4 on it anymore(mechanic says its not worth chasing it down as the last one he did was over $3000, and ours is not worth that!) BUT, it would do similar to yours for a long time, and the fix was removing a 30 amp fuse, count to 60, reinstall and it would work again-until it finally did not! HA Something about rebooting the electronics in it!

Sounds like it's all confused. Probably no damage done. Mine did that and I spent about two months sweating it thinking I had a big repair on my hands. I had to disconnect the battery to make another repair and when I hooked it back up it all reset and working great. worth a try.

Greg

I had that happen in the 04 dually. It turned out to be the ground strap from the transmission to the body. It wasn't making a good enough ground anymore to "complete a transaction".

I had a Ford F 250 with the 6.0 Powerstroke. In 2-wheel drive, it was useless in snow. Put it in 4 wheel drive ,it would go anyplace. I think it was because that engine was so heavy in the front

It would be best to have someone with a scanner to read codes for the transfer case module, the cheap code readers probably won't be able to do this. There are a couple service bulletins about the "service 4wd" lamp coming on, depending on what it's actually doing and what code is set depends on the repair. The bulletins state one repair to reprogram the transfer case module, the other bulletin states a concern with the dash switch being faulty. Keep in mind that it could still be something else.

Disconnect battery for a bit, reconnect and see what happens. I have cleared a lot of codes this way, and more often than not, everything is normal. Remember, there are computers in your truck, and they need rebooted from time to time just like your pc. I know your service guy would like the business, but I make that the last resort. BTW, I work down in Lebanon, and I44 was a mess this evening. Took me 3.5 hours to get home, and it is normally an hour drive for me. Saw more than one semi crossed up and in the median.

The 'puter may have lost contact with a wheel speed sensor for the ABS that is tied in through the 'puter to the electronic 4X4.

I got one newer vehicle like that, in which the 'puter can overrule me as to whether we are going into into 4X4 or not.

When the weather gets NASTY, I drive (and am thankful for) a couple of older 4X4's that have a lever on the floor that allows ME to decide if we are using 4X4 or not.

WHY have we "evolved" so far beyond that?