Im gonna try this on another topic area. the last one i had no replies. i started having trouble with my vents changing in my cab. now ive found out my 4 wheel drive dont work. ive checked all the lines and everything looks good. is it possible my vaccum pump and failed. if so will it hurt to keep driving it.

 

I had this same problem on my '95. Check the vacuum lines that run on the top side of the firewall and go down in between the brake booster and the fuel shut off solenoid. Just trace them to find any breaks or something that came unplugged.

One of mine broke in half and caused my vents to be stuck on defrost, 4 wheel drive didn't work, cruise control stopped working, and my emergency brake and ABS lights were stuck on. Added an old piece of windshield wiper hose to patch up the cheap plastic vacuum line and everything started working again . Hope this helps!

I tried to find an image to help where they are. But no luck. I know they are stiff plastic lines with rubber T's and elbows. Just be careful not to break them because they are very brittle. At least mine were!

 

x2 on the vacuum lines

 

I had a vacuum problem on my truck, it turned out being one of the vacuum caps on a tee being dry rotted and leaking. You couldn't even tell by looking at it until you took it off. Just a thought.

 

If you change the pump be sure and change the seal between the pump and ps pump. There's a guy in ebay who makes a double seal kit for it!! Best $60 I ever spent.

 

Easiest way to diagnose it would be a vacuum pump or Guages, will save you tonnes of time and money.