Vacuum Switch.

[Crewcab]

I have a 2001 Crewcab 4X4 4.3 auto. Can anyone tell me how the vacuum switch on the tranfer case works. My front axle was making noise like the locking collar was not fully dis-engaging. Pulled the bat. & tray & found the actuater pulled in, in both 2Hi and 4Hi. Pulled vacuum hose and actuator releases. Sounds to me like the switch on T-case is bad. No error codes. One other problem also vacuum related, My AC control panel keeps going out. I get the sucking noise from behind the switch. Replaced the first time, rebuilt old switch 3 times, and just got another under warrenty. Keeps going out. Could a bad vacuum switch cause fluid from T-case to be sucked into vacuum system. I have searched and not found an answer yet. Any help would be much appriciated.

[rlith]

When you hit your 4x4 switch, the encoder motor actuates and vacume from the switch on the transfer case pulls the vac servo under the battery tray...From your description it sounds likes its the vac switch. They are 15 bux in the help section of most autoparts stores. Takes about 10 mins to replace. (You just need a box wrench) Don't pull the hoses indivually. They are actually on a keyed dongle that slips over the switch. The switch is a common failure item for 2 reasons. 1st is that the check valve ball sticks as it wears. The other reason it can fail is that transmission fluid gets into the vaccume line..(there is a tsb on this, when too much gets in there you will see it coming out behind the ashtray)..