your "vaccum" switch where the vaccum lines hook to the trasnfer case. is broken, which means it is held open.
No it should not, It is now hooked to direct vacuum witch is wrong. It should be hooked to ported vacuum. That means that it only has vacuum when you speed the engine up and not when it is idleing.
where dose the vacuum under the battery come from
You can find a diagram for the vacuum system in a 1995 Blazer 4x4 will be located in the Blazer service manual. The manual can be purchased in most auto parts.
The 2001 Chevy Blazer vacuum switch solenoid can be found on the firewall in the engine compartment. The vacuum switch solenoid will be on the passenger side of the firewall.
It does not have one.
no
When this happened to me it was the three vacuum hoses on the transfer case switch were on wrong. There is a nipple on the switch and a hole in the vacuum hoses.
both, front engages by vacuum, transfer case is electronicaly shifted
Vacuum pump? Is this a diesel?
Need to know the location of the vacuum leak in order to answer this.
Get manual specific to that vehicle and follow vacuum routings
Start with a visual, inspect all vacuum lines for problems.