I'm trying to figure out what is wrong with my 4wd and have a few things ruled ou but not sure where to go next. First off, I have a base model which means the 4wd is lever operated. The problem came out of nowhere, no sounds or anything just no 4wd one day. When you put it in 4wd nothing happens but if you put it in 4-lo the low works fine but only in 2wd. So this rules out any problem with the transfer case.
The next place I went was the vacuum lines that control the front differential actuator. When shifting from 2wd to 4wd, the electrical lines going into the Vacuum Switching Valves do not change. They should switch when it is switched into 4wd. My thinking is that somewhere a electrical connection that is supposed to switch does not, resulting in no change to the vsv's, thus the 4wd actuator is not switching either. Does anyone know what connections are involved in making this switch?

The next things I want to try are a manual test of the front actuator, i read somewhere that I could test this easily but have not been able to find the directions, if anyone could point me to the right procedure that would be great.

Is there a way I can "hotwire" the vsv that is not getting power to see if I can engage the 4wd that way?

Any advice helps as i don't want to take it to the stealership and i'm coming up with blanks about how to proceed.

Thanks,
Marcus

 

Having a similar issue with my '98, no 4wd light and manual shifting into 4wd either hi or lo I can feel the transfer case changing but no transfer of power to the front wheels. Was working fine a few months ago and of course it snowed today and nothing

 

is there power going to any of the actuators?. i wired mine to a switch inside the cab. not because of any problems tho

 

Not sure on my end but it just happened and there is like 3-4 inches of snow on the ground so I am staying home. Will attack this later. I will come back to see the out come of powrider686's issue

 

Nothing yet, still trying to figure it out. Anyone with any ideas at all? I feel like the tunnel has no light at all...

 

Did you ever figure out this problem? I'm having the same problem........

 

When you move the lever into 4wd do you hear the relay on the passenger side footwell click? If not relay may be bad.
Next check the vacuum lines (should have two that go to the front acuater(sp)). One of mine snapped at the front diff, replaced both hoses and problem was fixed.
Hope that helps

 

If you want to test the function of the front actuator when the vacuum does not switch sides, just swap the two long hoses that go to the diff actuator. Label them before you do so you can put them back in their original position..

If the electric does not switch sides, the most likely issue are the sending switches on the TC. Sometimes they can be cleaned and function is restored. They are a pain to get to, but you need to get them out and test for continuity.

 

Instead of that I would pull the connector from the computer where the transfer case switch reports to and ohm it out there. Just download a copy of the FSM and save allot of headache going under the truck.