Need a little help!

[99BurbK15]

Hello, I'm new here so please forgive forgive me if I am posting in the wrong spot.
I got my 1st vehicle a couple weeks ago, which is a 1999 GMC Suburban with the 5.7 Vortec and the 4l60e transmission. When I got the vehicle I knew it had a 4wd problem. I think I narrowed the problem down to either the front differential or the transfer case but need some advice. Here is the issue I am having, when I put the Suburban in 4 Hi or 4 Lo and turn the wheel to the right or left and give it gas there is a clunking noise coming from somewhere. The transfer case is a NV246 and was replaced about 2 years with a low mileage case by a dealer, so that's why I then thought a differential. But the other problem I am having is around 50-60 when I let off the gas there is a very slight variation coming from around your feet in the truck, which I believe is the transfer case.

Did the dealer put a dud of a transfer case in? The Suburban only has 181k on it now and the case was replaced at 175k so it still should be good.
Is the front differential the one responsible? Could the bearings possible be failing?

Please let me know I would like to get this thing fixed before the snow flies.
Thanks to all in advance.

 

[GaryCCR]

I'm not a 4wd guy but if it clunks/clicks when it turns that's usually the cv shafts. At 180k probably time to be replaced if original.

 

[Hohns96z71]

I had a vibration from under the truck and it was the front drive shaft. It was wore out from sand and no grease ( thanks whoever had it before me). Try to move it up and down and see if it has alot of play. I would try the cv shafts first then look at the idler arm and pitman arm.

 

[99BurbK15]

Thank-you both for your help. After doing a little calling around I found a cheap but nice differential and thought I would see if that would solve it. I threw it in the truck and now performs better than is has in the last 8 years! I am going to take the old one part and see what caused it to make that noise. I will post pictures when I get it apart. Ben