The switch that screws into the top of the t case is messed up. Replace it and that will fix your problem.

i have fixed the lock collar with tacks on each side of it inside the axle. then disarm the fork. when you put it in 4 wheel drive she is in. :w2: no more vacuum to fool with and 4wd anytime anywhere when you pull it in inside.

x2 we just put the 4x4posi-lok one in my dads and it is awsome.no more problems. plus you get 2low(very cool)

Have the same thing on mine so far so good

Agreed. The posi lock cable is simple enough to install, and only about 200 bucks. You wont have to worry about 4x4 failing because of a vacuum problem again :tu:

i ran a two egr valves hook into the vacumm right out of the pump and they are wired to a toggle in the cab, only cost me maybe 40 or 50 buxs for everything at napa, works great and 2wheel low is nice for backing heavy trailers up steep grades

Take the vacuum control switch out of the transfer case. Then unplug the 2 vac lines that run down to the accuator. Start truck, see if you have vacuum on one of the 4holes on the vacuum switch plug- if you have vacuuum, hook vacuum control switch to the plug and press the button on the bottom of the switch while checking for vacuum on one of the 2 vac lines at the accuator. When you press and depress the button the vacuum should switch from one line to the other at the accuator. Mine ended up being a bad accuator. ($104+tax at Oreillys) vacuum control switch($17+tax) 4x4 indicator switch on accuator($4+tax) Hope this helps