hey silver dodge i got a new 4wd switch. and still blinks when i go about 45 mph+ . were do i start to trace down the vacuum leak.

 

Do you also have the blower vent/defrost issue I described?

I would start with the 4x4 vacuum actuator near the axle (see picture posted by Burning Rom above), and follow each line away from it to see if there are any holes or disconnected lines (should be 2 vacuum lines from it). Also, try doing a search on this forum for vacuum leak. Lots of folks have posted where they found their leak when they experienced similar issues. Some common areas are the vacuum lines going into the firewall near the heater core. There is a check valve that often goes bad and causes a leak. Seems to be a frequently reported cause of vacuum problems, so common there is even a TSB on it for some years. I have also read several who reported finding their leak in the vacuum line and cruise servo right under the battery tray. There is a pretty tight curve in it that goes into a 90 degree fitting. That elbow gets weak and brittle and can break, causing a leak. Pretty common from what I have read. Also causes your cruise control to be flaky. On mine, I had a leak in the line that runs along the passenger side frame rail next to the exhaust. Heat of the exhaust burned a tiny hole in it, causing my leak. Good luck.

 

i been driving my truck for last couple of days and no more blinking light. i was going to check for vacuum leak but i guess i wont intil light blinks again. you think just taking the old one out a replacing it got air in there. and lost vacuum . cause when i replaced it. it blinked the first two times when i drove it. now its fixed all the sudden.

 

Sounds like you probably fixed it. I would put it in and out of 4x4 a few time and see if each time it comes out completely, with the 4x4 light off. When I was having the issues, it would eventually come out, but the next time I put it into 4x4, it would start over again.