1995 2 door blazer, manual 4x4, the 4 wheel drive engages fine, but after moving for a few seconds/20 feet or so, it makes a loud clunk, and then the trans stops working as well and the car wont move until i shift out of 4x4. Any thoughts? My research suggests the actuator under the battery? Thanks for any suggestions.

 

Haven't had any luck with this, if anyone has any suggestions. The actuator under the battery tray seems fine. Don't understand why it works for a short time, then stops working, and causes the transmission to essentially go into neutral until i shift back out of 4x4. Should add that recently it did for the first time grind a little bit as I shifted into 4 wheel drive. Truck was in neutral when I shifted. Could it be the linkage?

Edit: I'm pretty confident it's the transfer case input seal. Maybe the switch too, replace that when I replace seals I guess. I'm assuming I would need to drop the transfer case for these repairs? Also have brake issues, and none of the heat/blower settings work very well except for "Vent." I'm thinking the entire vacuum system needs replacing. I've got a booster/master cylinder to put in, probably replace every vacuum hose, seals and switch....time to fire up the back up car guessing this is going to take me several weekends.