Mileage currently 8123 miles.
When I first got the Truck I was blown away . 24 MPG was the average
Now down to 3.1 13.9
Here is the seq of events
Day 27 of owning this truck , 352 miles on it , it was raining out terribly . Was on a highway at a red light , lots of standing water So i put it in 4x4 high rolled forward a few feet , light turned green stepped on the gas and two loud bangs, truck jumped up and down in the front rolled forward ,truck stalled. It would not start . Pushed it to the side of the road, Put it back into 4x2 started it. From that point the truck had a vibration in the front coming through the gas pedal and up the steering column. Noticed from that point on if I put it into 4x4 it would go in with aloud clunk and if i took it out it would take almost a mile before it would disengage. every time i put in 4x4 i was either at around 10-15 mpg. Bring it the purchased deal location and was told you cannot put in 4x4 while moving , I was like what???
Took it out with Service advisory stopped put it in 4x4 stepped on the gas , slipp slipp bang happened again . He said ohh that's the differential. Nothing we can do about it. My face dropped I said ohh yea there is (this is at 1200 miles now . left and took it to another dealer. they had it for a week,. dropped the transfer case changed out both cams on the front axles and reported finding moisture and rust build up on the gasket of the transfer case. They rotated my tires because the edges in the front are worn .. at 3600 miles?.. I tried to tell them its because its not the coming out of 4x4 even though it says it was but I got a funny look.

Well Vibration is now gone and it seem to ride back to normal , but on to the worse part.
Truck in reverse no gas pressure being applied , just normal idle speed it will surge going backwards , almost like the gear is oval , put in drive or start it and let it idle while sitting it will give a sudden bump and jump in rpm , like its missing Gas mileage is crap down to 13.1 to 13.9. Rough idle while coming to a stop.
Brought it in , No codes cannot help you ..
What to do .... now, besides drive it off a cliff

 

I think the owners manual says not engage 4 wheel drive on pavement for damage can occur, even if it is raining.

 

GOING straight ? That's interesting , So for years of using my GMC pulling boats out of ramps while in 4x4 had no issues , So ,I purchased a Truck that cannot do that ?

 

hmmm - I would continue to take it to different dealers. I know what a PITA that can become, but, from the info you provided something is not right and the right dealer should be able to tell you what is going on.

 

LTM I have taken it to two dealers so Far in New Jersey, How is it that something so known is being down played and in some cases they are acting stupid and playing the never heard of this before

 

THIS IS AN OPINION ONLY!!!

With that being said and knowing my information could be old and different now....

... I have seen dealers be hesitant, or downright refuse, to do some warranty work. There are, or were, incentives surrounding ratios of paid vs warranty work coming from a dealership.

Again - this is mostly based on opinion - but I have experienced multiple dealers refusing to cover an obvious warranty issue when another dealer did cover the issue under warranty with no questions asked.

 

This is why I tell people all the time not to use locked 4Hi unless they're on a surface that facilitates wheelspin (dirt, mud, ice, snow, algea covered boat ramp, etc). If you're on a surface that can go from hi traction to low traction in an instant (like wet pavement) it's best to use to 4Auto if the truck has it.

Today's half-ton trucks aren't like older trucks. They've got more torque and weight than old 3/4 ton trucks, but yet still use a lot of light duty components. If you aren't careful it can be very easy to break something.

 

Yea that is just part one
What about the poor gas mileage? and rough Idle

 

I had a turbo go bad on mine. It could be that.

 

How deep was the water? could it have gotten in the axles or wiring?
I never had a problem driving short distances in 4 hi. I've drag raced 1/4 mile in 4 hi

 

?? you most certainly CAN engage 4x4 HIGH while moving, straight from the '13 manual, see highlighted (page 219):





Now, 4x4 low is a different story:







However, keep in mind all of the following:

 

vacuum leak........heres why.....hubs are normally locked in, vacuum disengages them. If the hubs are locked in (whether or not its in 4x4) your fuel mileage will suck. Say you have partial vacuum (like a pinhole leak) thats when you get severe clunking.