2nd Gen Non-Engine/Transmission wont shift into 4wd

[tblb0900]

I put the truck on jackstands and front driveshaft spins when in 4wd. Applied vaccum to shift motor and it works fine. Could not find any bad spots in vaccum line and have good vaccum at transfer case vaccum switch, but little at shift motor. Pulled switch off of transfer case, plunger seems to work fine and is not sticky at all. I blew into ports on switch with a straw and air flows freely and switches ports when plunger is pressed. The only thing I did not look at is the check valve unless there is something else I am missing. Can the check valve be the problem or should I recheck for vaccum leaks? Also, Is there a better way to check the switch?

 

[JMcCoy]

That is why I got rid of the vacuum CAD and installed the Posi-loc cable system. Did you inspect the vacuum line at the passenger side fire wall, and under the dash board? Sometimes the lines will go bad at the AC vent diaghrams as well. Good luck.

 

[WilsonF]

With truck running, pull vacuum connector off of CAD motor have someone shift in and out of 4wd you should feel the vacuum shift from one line to the other if not check your switch on the transfer case.

Floyd

 

[tblb0900]

switch seems fine, and no I only inspected the vaccum lines for the cad, but I had good vaccum at transfer case switch. Lost vaccum between switch and shift motor.

 

[HHhuntitall]

If the lines ever get knocked off, they can get sand and dirt sucked up in them, and stop up. Both lines pull vacuum. The red when in 4x4, the black for 2wd. And the one without vacuum acts as a vent through the switch and if one is stopped up, it won't let the actuator move far enough to engage; it will do the same if the vent is stopped up, as it won't let the diaphram in the actuator move because there's a vacuum on both sides. The vent is up by the back of the engine under the fuel filter, if it's still factory; it runs from the t-case switch up the bell housing. I have this happen all the time on the ranch trucks, as the brush will drag a line off, and it will fill up with sand, or the vent will get stopped up with sand.

 

[madmanmanick]

had the same issue with my truck, there is an electrical line from the indicator lamp switch on the vacuum shift mechanism on the front axle got severed. Once I spliced the cable together it worked fine. Hope this helps.

 

[WilsonF]

Pull the vacuum lines off the transfer case and the CAD motor and blows them out w/compressed air, see if that clears it up.

Floyd

 

[WBodine]

I had the same problem a few months ago. It took me awhile to find, but it was in the vacuum lines where they hook to the transfer case a few inches from the switch one of the lines had split. Cut and spliced problem fixed. Hope this helps...
Bodine