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2004 F150 fx4 really stumped on my non-working 4wd
I replaced the solenoid last year when it wasn't working and that fixed it last year. Now this year I have no vacuum at the solenoid, and when I Jack it up and turn the wheel the half shaft turns as well. I get a 4hi light but only the rear wheels spin. So no vacuum and no 4wd.
The vacuum part would be pretty easy. Just trace the vacuum line back while the truck is idling and find out where the vacuum starts working again. Could be a plugged line, a disconnected line, ect. Did you put it up on a lift to make the back wheels spin but not the front? How did you test this?
If you're not getting vacuum AFTER the solenoid then you solenoid is bad. Sometimes parts just don't last. Is the solenoid an updated one with a rain shield over it or the older style with no shield?
Like so^^ or like so so vv
Last edited by BadFish523; 01-16-2017 at 02:01 PM.
There are also some check valves in the system that have been known to plug up. Taking them off and blowing some air through sometimes helps but they are cheap to replace as well.
No vacuum through the line feeding into the solenoid, I'll look at the check valves. No lift, we had snow here and only the back wheels would spin. I jacked up the front end and turned the wheels and the half shafts spin with the wheels which makes sense with no vacuum. It doesn't make sense to me why the 4wd wouldn't engage if the hub's are locked in at all times.
That means the transfer case shif motor is not working.. you may have several problems.. all the vacuum is for is to engage and disengage the wheel ends..check fuses.. btw there are a couple under the hood also for the 4WD system.. check your vacuum box for cracks and make sure the lines are intact.. no cracks.. this would be the lines running from the vacuum box to the solenoid... it has the check valves in it.
Thanks for the help, I'll look into all of that as soon as I can. I thought it was the transfer case shift motor as well and had a spare that I bought last year when I replaced the solenoid. When I took off the original the system was in 4hi, so I had to hook up the electrical on the motor to switch it to 4hi before installing it. So that is good.
That means the transfer case shif motor is not working.. you may have several problems.. all the vacuum is for is to engage and disengage the wheel ends..check fuses.. btw there are a couple under the hood also for the 4WD system.. check your vacuum box for cracks and make sure the lines are intact.. no cracks.. this would be the lines running from the vacuum box to the solenoid... it has the check valves in it.
Not necessarily if he has no vacuum into the solenoid.
Start working your way back on the line leading into the solenoid. Pull off each check valve and check again for vacuum. Otherwise you have a leak somewhere and that is not good for engine performance and efficiency either.
01-16-2017, 01:42 PM
2004 F150 fx4 really stumped on my non-working 4wd
