Stats:

97 F150 4x4 XLT, 200k+ miles.

A few weeks back I finally replaced my brake booster. It was hissing like a freakin' snake for weeks but...well...who wants to be outside in frigid temperatures messing with stuff like that?

Finally I got tired of the hazards of a failing brake booster and changed it.

Now my 4x4, manual shift, will not engage. And soon I will need it in this Indiana weather.

I googled enough around and searched this site enough to figure out the 4x4 shift is actuated by vacuum.

I'm assuming something got screwed by the failing brake booster but I can't figure out what.

Now it's not totally gone, I suppose. I did get to work once and managed to shift it into 4x4. When I shifted it out, the 4x4 light stayed on but I could tell 4x4 was not engaged.

Any ideas of what to check for?

Should I really consider buying a new Ford?

Should I just ride out the winter and worry about this next year?

 

Just a shot in the dark on this as I'm certainly no expert on the 4x4 system. Since you obviously had a vacum leak at the booster is it possible that you got some moisture in the vacum system? With the cold temps we are seeing the moisture could freeze in the vac lines, blocking the line and preventing the 4x4 from activating? Just a guess here. Anywhere you could park the truck in a warm enviroment and see if it works after thawing out? I guess I'm asking more questions than you are.... Good luck.

 

The most likely culprits are a vacuum leak, faulty actuator motor or faulty solenoids. Do you have a vacuum pump?

 

Problem solved: The linkage between the manual shifter and the transfer case arm was all the hell froze up.

I see the problem but it's too cold outside to be messing with it so I'll have to wait until tomorrow to try and fix it.

<thinking aloud> Maybe it's time to get a new F150