Something's Wrong With My 4 Wheel Drive

[Klowns]

Every time I hit the switch to move it into 4 wheel, the light engages and stuff like it should, but it doesn't actually move into 4 wheel. I took it down to a shop, and they screwed around with it for a while, and they said that they used a hand pump to simulate the vaccuum that occurs when you move the switch. They said that the little gear moved over and it popped into 4 wheel drive.

Just wondering what my problems might be here.

1) Perhaps broken vaccuum line somwhere in there?
2) Something came loose and the switch isn't actually turning on the vaccuum?

Just 2 things I pulled off the top off my head.. Anyone else had this problem, or atleast have any ideas of what I might look into.

 

[TPLYNCH]

Are they talking about the vacuum on the front differential?? Or are they talking about the shift motor moving?

 

[Klowns]

I'm not sure, whatever the vaccuum is, that makes the gear move to pop the front into 4x4. That's what they said they did, with the hand pump or whatever, just put it up there pumped it, and it moved the gear over and it popped into 4x4.

 

[dogfriend]

Check this post by mikefox: Dead Link Removed

There are links to the 95-96 Control Trac drawings and schematics.

I think what the shop tested was your vacuum disconnect which engages/ disengages the front axle. They are saying that the vacuum part works ok. There are two electrical solenoids that control applying vacuum to the axle disconnect. If one of these solenoids is stuck/not working then that would prevent the vacuum disconnect from working with the switch. It is also possible for the problem to be in the switch or the GEM (generic electronic module).

I would see if the 4wd switch will operate the vac disconnect. If not it may be an electrical problem. If it is a vacuum hose leak, they should have been able to test that with the hand pump also.