4x4 solenoid
 

Had the truck in a local shop recently for some other work and asked them to look at the 4x4 which quit working last winter. They told me the solenoid was bad and needed replaced. At the time I didn't know there were 2 so didn't ask. Over the holidays I had time to go look at it and after doing some reading on here found out to check for vacuum.
My problem is I took both lines off and they both felt like the had equal amount of vacuum. So I guess I should ask do I need a vacuum gauge to determine which one it is? Do you check it when the switch is being turned or at any time? Is it possible both solenoids are bad? And lastly for those who have already replaced theirs, how much did Ford charge for them?

Each solenoid supplies vacuum at different times. One engages the front diff when the vehicle is put into 4x4. The other disengages the front diff when the vehicle is put into 4x2. They should have vacuum depending upon the position of the switch/lever. I believe, but not 100% sure, the outboard solenoid engages, and the inboard disengages. Best way to check is put a vacuum gauge on each individually and see which has vacuum when you move the switch/lever, naturally engine running. I would be very surprised if both are bad. Also if your vehicle is still not going into 4x4, check the lines for leaks, check the vacuum motor on the diff is working and check to see if the fork in the diff is free and does indeed engage/disengage the front diff.

Thanks for the info. It may take awhile for me to figure this out due to my work schedule. When I checked it this morning it had the same amount when it was in 2x4 and when it was in 4x4hi, but I checked it when it was in each position. I'll have to run out and get a vacuum gauge and have the wife turn the switch. At any rate I'll start there and work my way through each item.

I should have asked before. Does the 4x4 light come on and does the front driveshaft engage. It could be other things if these are not working.

No 4wd
 

My 93 V-8 with AT won't go into 4wd. When I push the 4x4 button on the dash, the alternator guage swings over to C for a second and that is it. 4x4 light does not come, truck is not in 4wd, nothing else. The alternator gauge action indcates to me that something electronic is working and something mechanical is not. Any help?

You might want to start a different thread, the 93 and the 97-03 are totally different on how they work.