02 ZR2 transfer case clunk

When I put it 4wd I hear a clunk and drives a little bit then clunk again, drive short distance and clunk again....etc......! Sound and feels like maybe it is not engaged all the way OR maybe has a broken tooth off a gear OR ?????????. Any help on what to check .:banghead:

Thanks

2002 ZR2 extended cab 4x4

change this it is on top of the tranfer case it has 3 vac lines runinng to it



you find it in the help sec at advance auto parts

http://www.partsamerica.com/productdetail.aspx?MfrCode=RNB&MfrPartNumber=49315&PartType=863&PTSet=A

Thanks .........I'll try that.