CV joint noise?

My yukon is making a serious, clunking noise when in 4hi and turning either direction. It sounds like it coming from the left front wheel but I'm not sure. How would I check the CV. It doesn't sound like a bad CV on a little front wheel drive car. Could it be something else. Front diff?
Any help would be greatly appreciated.
any guesses?:skep:

does it make any similar noises in 2wd? if so suspect a bad cv. when in 4wd it makes the noise going straight? also check front driveshaft universals.

Does it make this sound in 2 wheel drive?

For my 99 yukon, if i made sharp turns in 4wd, the front would make a horrible noise.. but in 2wd it did not. I found that sharp turns on dry pavement in 4wd was the culprit. I dont run the truck in 4wd unless its snowing or muddy or somthing..and I havent heard that sound since. :skep:

It only makes th noise in 4 hi. Don't know if it does it in 4 lo. I jacked it up in 4 hi today, but it doesn't seem to have any major slack on either side. Anyone know anything about the autotrack (np 246) transfer case. I also checked the front U joints. Any more ideas? Thanks