I need help. I am on transfer case replacement number 6. I have a 2004 gmc Sierra k2500 HD, 6.0 gas. I have used multiple different remanufactured transfer cases from different companies etc. I have even had different mechanics look at it. Most I have for is 12k out of a replacement. I have had driveline checked and balanced, new u joint, new shift module. I have had different driving conditions on all cases such as pavement, towing on pavement, dirt roads, etc. I need help. I can't afford to sell cause it is paid off. Any suggestions????