2000 blazer np8 transfer case problem
 

Hey guys. Wonder if anyone can help with this. I have the 4-button (with Auto 4wd) transfer case and it always stays in auto. It shifts through 2wd high, 4wd high and 4wd low but always ends up going back to auto all by itself. I've had it to 2 different transmission places and have replaced 1) the buttons 2) the encoder 3) the tccm module (actually swapped with a buddy's blazer - the upgraded module, not the original hi failure one). Nothing has helped. Has anyone heard of this problem before? Any help would be greatly appreciated. Thanks in advance.