My question is this, I unplugged the blue and pink vacuum hoses that go to the fire wall from the 4x4 acuater, the pink one has vacuum all the time but the blue one does nothing, I tried advance auto they need a part num!! to order a new vacumm cylinoid?? I dont even know its proper name but there is two of them next to each other they have plugs on top of them then vacuum hoses.. thanks to who all repls!! much needed

 

I just bought both solenoids two days ago for my 98 F150 and you have to get them from Ford. They are around $40 apiece. Make sure that your actuator on the front axle isn't the problem first.

 

check the vacuum at the cylinder on the axle. one hose has vacuum when in 2 x 4 selector and the other hose has vacuum when selector is in 4 x 4. that makes the cylinder piston go in and out.

 

https://www.ford-trucks.com/forums/9...2-f-150-a.html

 

One solenoid passes vacuum when in 2WD, the other when in 4WD. Make sure the vacuum path changes when you shift into 4WD before you buy a vacuum motor(diaphram).


https://www.ford-trucks.com/forums/6...nt-engage.html

 

Another question all info so far very helpful!! is there a way to check to see if the switch on the transfer case is sending signal to pump to engage 4x4? wanna make sure its the problem before I buy a new pump.. thanks to all for all your help!! when I switch to 4x4 the pump from the blue line does nothing!!

 

You have the manual shift transfer case?

 

yes MSOF on the floor

 

so today I switched the vaccum lines on the acuater, putting the pink one were the blue one was etc.. It fixed my 4x4! egaging it when in 4x4 and cutting it loose in 2x4 everything seems to be fine.. ????????????? The lines are cut to fit and I can tell its not supposed to be this way????? any ideals?

 

You have a bad 4wd solenoid. As it is your front axle will be locked in all of the time. Pick up a solenoid, put the lines back where they belong and you should be good to go.
Didn't remember but from this pic it looks like my 2wd solenoid was bad.

The one you need to replace is the one closest to the fender.

 

Im sure its vacuum solenoid! The only downfall, running it with lines on the acuater switched is I have to come to a complete stop in order to release 4x4. Other than that Im rolling with it for a bit I just replaced header gaskets in it yesterday and the more work I do to this truck the more I love it, before ford trucks I was a JEEP guy, but now when I go to my jeep friends house I park my stock f150 next to a lifted, big tired jeep and I sit level with it

 

Pick up a set at the salvage yard. They're the same on an Expedition too.