Hi Waterdowg, sometimes I had this sound when starting drive, specially on mud, other times was at low speed with the automatic 4x4 on. Since I selected the 4x2 mode anda changed the front axle oil it has stopped, but I am not using so much the car until the bearings arrive.

 

I'm not sure what it was. My ABS is now working correctly and there is no more noise. The noise would happen right abou the time the ABS pump should activate. From what I read teh ABS pump cycles as soon as teh you 5-8 mph for just a second or two. This is exactly when min happened. Plus I would see a dimming of the light when it happend. Which does not happen anymore. All is normal. My 4wd works fine in Auto and 4 High. It did have an ABS code but I have not had a chance to look again I got the computer back just have not had time to check. But I think my old code was CO265????

 

Somewhere I read that the CO265 ABS code is poor connection or no ground in the module, you do not need to repair. Also check for the battery and alternator conditions.

 

I was able to get it on the computer yesterday to check for the code. The Code was C0268. I cleared the code and took it for a drive. Still no cose or light.

 

That is good Waterdowg, I hope it has disappeared, but, in case it appears again, try a logo at the car grounding and ABS connectors.
I had also found a post in another forum describing the reasons for this code.
Here is the link: C0268 ABS Code - Ask the GM Technician - GM-Trucks.com

 

Thanks thats some good stuff. I think in the spring I will run a dedicated ground.

 

Have you read anything about wheel bearing issues for this vehicle?

 

No I have not looked in to it. Not sure how that would apply. I seem to fell my issue was electrical. Since the crunch noise would only happen at once. Here is how it went:

Start Truck
Put it in either Drive or reverse.
Go about 5mph
Hear the noise, lights dim, and ABS light comes on.
Never hear the noise again until I restart the engine and repeat the above steps.
I were to drive stop put it in park and not turn off the engine, then start to drive again I would not hear the noise.

How can a wheel bearing cause this? I'm all ears and open to suggestions. Just don't see how its possible. Is it?
I would like to hear some feedback on if this is possible so I can look into it. I never did get a soltion it just seemed to fix itself. or at least there is no more noise or ABS light.