Would like advice from someone who has experienced or is familiar with this.

I am experiencing difficulty with engaging the 4 x 4 on this truck.

I have an F150 4x4...2001, with the electric transfer case shift moter and dash mounted selector switch. This is what I have observed so far, and what I have checked.

The truck will go into 4x4 hi mode occasionally if I switch when stopped and 'ease' forward slowly. But then it will drop back out again after a brief period of time.

It never seems to engage the 4x4 in low range, although the transfer case will shift into low.

The vacuum 'motor' located on the front axle is clean and free of obstructions and seems to work. I have observed it moving in and out when using the dash switch.

I have supported the vehicle with jackstands on all corners and observed that when the unit did occasionally engage the 4 x 4 drive, the front drive shaft rotated. During all other events it would not. By that, I mean not engage during most instances of selecting 4 high...never in 4 low and not after it seemed to 'drop out' of being in 4 high for a bit.

So if the front axle vacuum 'motor' is working, and the transfer case electric shift motor is operating such that it will drive the transfer case into each of its 3 ranges....2 high, 4 high and 4 low, what else is preventing the 4 x 4 from working properly?

 

Just a guess. Sounds like the shift fork in the transfer case is worn out or broken.The shift fork is inside the case.
Hope that helps.

Mike

 

I had a (very) similar problem with mine ('98 Expy) and even though the vacuum motor was in fact moving the lever, it still turned out to be bad. I did the diagnostics and everything was working well up to the front differential. After noticing the vacuum motor working I was positive it had to be inside the differential so I took it to Ford. Well, an hour of labor at $90/hr (*gasp*) plus I forget how much for the replacement vacuum motor and it works good again. (Perhaps the bad one didn't move the plunger out enough not moving the lever all the way?)

So, you may want to try that first if you can get our hands on one for cheap. I don't believe they are that expensive so it may be worth a shot to replace it. In testing, I actually took mine out and put it back and it wasn't a big deal at all -- remove the protective cover, look behind the rubber boot and you'll see a spring clip - remove that and the 2 vacuum lines -- install new one in reverse order and you're good to go.

BTW, a good site for OEM parts seems to be the following:

http://www.fordpartsonline.com

Here's a link to what I "think" is the vacuum motor for your truck, in case you wanted to try it. (Verify the year, model, and part as I just did a quick search)

http://www.parts.com/partlocator/ind...01&catalogid=1

It's listed at $39.14

Good luck and post back if you find an answer.

 

Thanks Aycardus,

Some great tips! I haven't had a chance to get back to it yet.
But am thinking to attack in this way.

Carefully inspect vacuum lines again and/or replace the cheaper of the 2 vacuum solenoids, which is the clutch relay sol. dlr. price here at $14.50

If that's not it, then the axle Vacuum motor. dlr. retail at $68.50

(I'll take it for dealer diagnostic if necessary but would rather save the $80 if the cheaper stuff gets it first.)

Then perhaps the transfer case shift motor and/or relay
(much more expensive)

I'm checking out the online parts sources you mentioned as well.

I'll post my results....

comments anyone?