I have been searching ths form for about a week and have not been able to find this same problem.
When I put if in 4x4 high, it does not engage. It clicks in the dash like it always has but I never feel it engage and on ice, the rear end tries to pass up the front constantly.
I tries it in 4x4 low and it seems to kick in and start out but then lick out (Sometimes).
I had seen a thread earlier in the week that talked about how to check the two vacuum controls under the hood but could not find it this morning. If someone could go over that again, I would really appreciate it.

 

I took it out and tested it again.
When you put it in 4x4L, while in neutral and my foot on the brake, its seems to lock in. It click and then I feel a light clunk. Once I stop, put it back into neutral, and switch it back to 4x4H, I hear another light clunk.
I hope this helps.

 

Does it engage in 4 low and 4 high ? Is the transfer case engaging? What year is your truck? This would help. From 1998 to 2001(?), vacuum was used for 4x4 on the front axle:a vacuum actuator with two solenoids mounted on the passenger side firewall. Ford then switched to a vacuum engage/disengage system at the hubs. Does the 4x4 dash light come on ? In 2WD drive,with the front end off the ground ,you should be able to spin the front tires by themselves. With the truck in 4WD,front tires off the ground,rear tires blocked,put it in 4WDH neutral : as you turn a wheel by hand the other tire should spin in the opposite direction. If not ,check vacuum lines and/or the actuator.

 

Sorry for the lack of information.
My truck is a 2001 F-150 Super Crew with the 4.6L Triton V-8 with 149,000 miles.
I am not sure if the transfer case engaging. When I switch into 4x4, the 4x4 light does come on on the instrument cluster and I hear it click twice.
I understand about the vacuum engaging system as I had read about it in other posts.
Unfortunately, they are forecasting 4"-7" of snow tonight and I will not have enough time to check it when I get off work. But I will do what you suggested this weekend.
Early yesterday evening, we got some snow showers that put a dusting on the road. I had to run out so I checked it again. I came to a stop and stepped on it fairly hard and they rear tires broke loose. So, I switched to 4x4 (I could not feel a clunk or it engaging) and stopped again. This time, the rear tires still broke loose but it started moving forward better but not much.
I know this sounds weird (And I am having a hard time describing it) but, the last time I needed 4x4, everything felt positive. I felt a slight clunk and I could definitely (NO doubt) tell it was in 4x4.
I am not sure if the helps or not but, this past summer, I drained the transfer case and rear differential and replaced the fluid per the mfg spec's. I had bought this truck used with 40,000 mile and this had never been done. And, yes, I know it should have been done earlier. Blame it on a brain fart and lack of paying attention.
Can you tell me hot to test the solenoids and actuator? For some reason, my repair manual does not cover these.

Thanks for your help!!!!!

 

my mom's 1998 Expedition XLT 4x4 has the exact same problem... the light comes on, you can hear, feel it (in 4Lo) click, but it doesnt work. Hers has 150K miles on it. The mechanic we take our trucks to even said he fixed it, but ah... I couldn't tell... I got stuck too many times while driving it where I needed 4wd. So I'm gonna keep my eye on this thread too. Thank you! Someone finally posted a thread on this! I was too lazy to do it myself, lol.

 

Wingman:
I hopefully someone can help us that is familiar with this system. There is nothing on this truck that I would hesitate to fix but there is no sense in just replacing parts hoping to stumble onto the problem. I have put together cars and motorcycles from milk crates full of parts but I want to make sure of the diagnosis.
I suspect it is either the solenoids on the firewall or the electrical switch on the transfer case but I am not sure of the proper procedure to check them. My repair manual is definitely lacking in that area.
Keep your fingers crossed!!

 

I had the same problem on my 04 (new style though). I'm willing to bet you have a bad hub. Also check out your actuator and vacuum solenoid. Thats what was wrong with mine and I still havent fixed it to this day. But I would say the hub is whats probably messed up.

 

Trogdors4x4:
Do you know the proper procedure for checking the solenoids and/or actuator?
Thank You for your input!

 

Ther are two solenoids on the firewall. the one on the right controls the 4x4 actuator.Jack-up the frontend ,remove the three bolts that hold the actuator shield in place. You see two vacuum lines:a red or pink one and a blue one.the pink vacuum holds the front axle in 2WD. The blue gets vacuum when you switch to 4Wd and the shaft engages the right axle fork which in turn gives you your front drive. Turn engine on after pulling the two lines off first. In 2wd,in Park and in idle, you should feel vacuum on the pink line.Now switch to 4WD: vacuum should now be present on the blue line.If either line has no vacuum during the testing,backtrack for vacuum leaks or replace the solenoid.

 

Johnny:
Thank You for your help.
I will try that this weekend.
If everything there is OK, do you how can I check the actuator?
Hopefully I can get to work tomorrow. They are predicting 4-10 inches of snow tonight through Wednesday morning.

 

Yeah,6-10 in upstate NY. To do it right, you have to get all 4 wheels off the ground Use jack stands With engine running, put foot on brake, put in D and in 2WD Only the left or right rear wheel should be turning. (It would help to have an assistant).Brake, put in 4WD,put in Drive: the transfer case/front axle should kick-in and the front tires may or may not be turning. If you see the front drive-shaft spinning,the transfer case actuator is OK. While in 4WD, the actuator shaft should EXTEND.(But slowly: remember ,Ford uses the retarded vacuum assisit!!!!!!!) continue on next post.

 

OK. To remove/test Front Actuator : Front-end up,remove actuator shield (3 bolts 10 mm), pull the vacuum lines . Pull back the actuator boot-shield ,remove the E-clip (losts of WD-40 or PBC Blaster spray on the clip !) and pull away and back on the actuator to remove the indent from the axle-paw.The shaft on the actuator should move freely (it does not!! Oil from the engine jams the shaft : spray and work the shaft . If it feels f**ed -upor not moving smooth ,replace actuator ($105-$135) .Install in reverse. hint: install with shaft fully extended,plug both vacuum ports while installing E clip.

 

Johnny:
Thanks for your help.

It might be a while before I can do this. We had 4" snow yesterday, 1"+ of ice last night, & they are expecting another 4" of snow this morning. Limbs down everywhere (Including on our cars). Then, cold temps and light snow through Monday.

I will post a reply once I get a chance to check it out.

Thank You again!!!!

 

I have recently experienced this same problem wit my 01 SCREW. The problem occured during the recent cold spell -20C to -25C. Now that things have warmed up to about 0C, everything seems to work fine. I know the 4X4 is working fine now because when I try to make sharp slow tuns on pavement the front end wants to jump due to the wheels fighting each other. I sure would like to know what the root cause of the problem is. Hopefully it won't come back at the next cold spell, but I'll keep you posted.

 

Marpeg:
That part sounds like a good cleaning with WD-40 or Deep Creep (This stuff work excellent) might be in order.
Unfortunately, we isn't working even when the temps are well above freezing.
Hopefully all the snow will melt around here by a week from Saturday and I can get my checked out.
Good luck!!!!:o