problem with my 4x4

My vehicle is a 99 jimmy with 4 button system.
Ok here is what happens, the truck starts out in 2hi I press the 4hi button, I hear a click from the computer on the right side, now the 4hi button
continues to blink, it will continue to blink never switching back to 2hi, now if I press the 4lo button the 4hi will stay on and the 4lo will come on, but when I put it in gear only the rear end is in 4lo, the back tires will spin in 4 lo but the front end has no power.
It is as if the valve in the front under the battery box isnt working or I have a vaccum leak. Any suggestions?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Take it to a reputable place for a free estimate.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.