So I have a 94 pickup, 4x4 automatic. I'm having trouble getting my truck to lock into 4x4 high and low. I'm not sure where to start, haven't been able to find a book for the truck at my local shops. Just wondering if it could be the transfer case, a vacuum leak or what? I can get the truck to go into 4L but when it shifts gear it feels like it's popping out of 4x4 and 4H isn't really doing anything. Any ideas?

 

Ck your hubs see if there locked?