So it appears i have the same problem as everyone else here. The 4WD on my 97 F-150 wont engage. Ive checked both solenoids on the top of the firewall, and both of them have vaccum. The lines down to the "diaphram" on the transfer case have vaccum also. (did the check with a friend inide the truck). I can move the diaphram back and forth by finger, but when i put the lines back on...... nothing. I tried cleaning out some of the crap on the linkage such as dirt and grease but nothing seemed to work. Do i need to replace the diaphram or is there a way i can just take it off and fix it? I was thinking about running an air compressor to it and seeing if i can just blast the grime out of it.

Any help is appreciated. Snow storm is coming shortly here in MA and im gonna be driving through it. Thanks


edit - when i start the truck, and put the lever into 4wd, the diaphram doesnt move.

 

I dont know of any tricks other than to replace the diaphram.


Sorry I couldn't be more help.

 

When you say you have vacuum to both solenoids, do you mean you have vacuum coming OUT of both solenoids at the same time? You should have vacuum to both solenoids from the intake manifold, but on the lines that run down to the CAD, you should only have vacuum on ONE of them at a time. If you have vacuum on both at the same time, there is no pressure difference and the actuator isn't going to move at all. You should have vacuum on one side, then when you switch to 4wd, you should have vacuum on the other.

Make sense?

-Joe

 

I have a 98 expedition and the front tires will not engage but the transfer case will. Did you find the problem?

 

Hello Guys. This Is My First Time Posting So If You Will, Please Bare With Me. I Had The Exact Same Problem With My 2003 F-150 Fx4. The 4x4 Light Would Come On, However It Would Not Engage. I Checked The Solenoids For Vacuum, They Were Okay. I Checked The Lines, They Were Okay. I Checked The Diaphram, It Was Okay. When All Of These Checked Out, I Was Not Sure Where To Turn. As A Last Resort, Took The Truck To A Ford Tech. I Told Him About The Problems I Was Encountering And What I Had Already Checked. He Told Me That It Was Most Likely The "shift-fork" In The Front Diff That Had Gone Bad. After One Hour In The Shop, I Got A Call From The Tech. He Said That The Problem Was The "shift-fork". I Went To The Dealer To Get A Look At The Shift-fork Myself And Sure Enough, The Two Tabs On Either End Of The Shift-fork Were Worn Off. He Said This Was Most Likely Due To Heavy Use (shifting The Truck Into 4x4 While Rolling). Even Though The Manual Says You Can Do This, He Advised Me Not To. He Said That It Is Important To Come To A Complete Stop Before Engaging 4x4 (manual Shift). I Do Not Know If You Can With The Electronic Shift. I Hope My First Post Will Be Of Help To Some Discouraged Person Out There Like I once Was.
Dave K.

 

I would have to respectfully disagree with the tech. If everything is working properly, the lock-up collar will be turning the same speed as the shaft that it engages, so the relative speed difference between them is still zero. I don't see how having the vehicle moving when the front axle is engaging or not would make any difference on the shift fork itself.

Additionally, Ford designed the system to shift on the fly. Why in God's green earth would they design a system knowing full-well that it couldn't do what they intended it to? That's just begging for a class-action lawsuit right there.....

-Joe

 

Joe- I Understand What You Are Saying, However I Am Just Telling You What The Tech Told Me. Should I Be Looking Into The Problem Deeper? What Are Some Other Reasons As To Why The Shift-fork Was Shot. Thanks, Dave K.

 

Actually, I just looked at it a little closer, and while I wouldn't completely disagree with the tech's diagnosis, I wouldn't completely agree either.

Heavy use of anything on the truck can cause it to wear out, the same way heavy use of the truck itself can cause the truck to wear out. The nylon fingers cna wear for a variety of reasons, the least of which is simple wear and tear from use. However, I know many people whose trucks are used in snow 6 or more months out of the year, and they don't have problems like that. As I said before, the way everything is designed, the wear on the fork should be very minimal, and it should never be under a lot of strain, so long as the rest of the system is working properly (i.e. the transfer case should engae first, before the lockup collar to synch the shaft speeds).

The first thing that comes to mind is the coupler gear (the one that the shift fork moves) hanging up and not moving properly. That would put pressure on the fingers at all times. A good technician would have gone the extra step to see which side wore out first (engage or disengage), or if it was a catastrophic failure of the shift fork itself by examining the old part(s).

I guess what I'm saying is that it's not necessarily a correct diagnosis to say that the parts wore outbecause of overuse, but it's only one of the possibilities. If that's what was claimed, I'l like to see the evidence as the simple wearing of the fork isn't enough evidence in and of itself.

-Joe

 

Joe- Thanks for the help. What I plan to do is get the tech a call and ask him if there are any other reasons why the shift fork went bad other than usage. I will also ask him about the coupler gear and if it is something that should have been replaced as well. We will see what he says next time, I will keep you posted! Thanks again Joe, Dave K.

 

I meant "give" the tech a call not "get" the tech a call. Sorry, I am still working on proper word choice! Ha! Ha! Dave K.

 

Dave- Did they replace the fork for you, if so does it work now?
Thanks Joe Wilson

 

I would take another look at the vacuum lines to the diaphram. On my old '97, my 4x4 was out and went to mechanic. Told me it was wither the shift fork or the electric motor in the t-case. He told me for about $400.00 he'd have it fixed.

I told him to bug off and came to these boards. Checked my vacuum lines and sure as chit, one had a gaping hole in it. You could feel the vacuum leaking out of it. I used some electrical tape...tada! 4x4 engaged. To really fix it I went to Advance Auto, bought 6" of vacuum tube with the i.d the same as the truck's vacuum lines o.d.

Just made a clean cut of the busted line and shoved it in the ends of the new "patch". Worked like a charm....and for less than $2.00......f'n local garage tried to steal from me.

Hope this helps. BTW, the hole in the vacuum line was right by the battery which I probably cracked when I replaced my o2 sensors

Good luck.

 

Joe- The tech did fix the shift-fork for me. Since then, I have had it in and out of 4x4 many times and it works perfect. Finally, I don't have to worry about getting stuck! Thanks for all the help guys! Dave

 

How much was the shift fork ? and does it come as an assembly ? I read something about it before and remember some 'kit' ? I'd love to come pick up your old one if you still have it , and make a couple out of steel or aluminum. I have a lathe and a milling machine. Dennis

 

Dennis- The stange thing is, I did ask the tech if I could keep the old shift-fork. As I expected, he said no because they are required to send the old parts back to FORD because the parts were covered under warranty. If I did still have the kit, I would ship it out to you. To answer your other question, I don't know the exact price of the kit (the shift-fork, a few gears and what looked to be some kind of metal sleeve), due to the fact that it was warranty work. However, I was told that if my truck was out of warranty it would have been around $1,000 big ones for the parts and labor. Dave