Hey fellas-

Has anyone had a problem with that vacuum motor that engages and disengages the front axle in 4WD?

I have replace mine twice and it failed on me again this weekend. I was running some mud with a couple buddies and after I had a bit of trouble with one mudhole they asked me why I was still in 2WD. I said I wasn't and realized I had lost the motor again. So, I was force to climb under the truck in the mud and use zip-ties to hold the lever on the axle over (cool fix, but laying under the truck wasn't so cool). It held for the rest of the day and I am planning on getting one of those posi-locks.

Anyway, what is your experiences with this?

-Abrams

 

My brother had the posi-lock put on, he broke three, all within a couple uses, he went back to vacum.

 

Mine froze one time, but after it warmed up a bit, it was fine. Other than that, no issues so far.

 

Have you ruled out vacuum leaks? If you are able to shift the linkage by hand and use a zip tie to hold then the problem is not the linkage. If you have a vacuum leak you may be slowly loosing vacuum to the engage side of the vacuum motor. it could also be a vacuum solenoid that is malfunctionning. Have you tested the vacuum motors after you remove them?

Regards

Jean Marc Chartier

 

I know the problem isn't in the linkage. It is in the motor itself. It seems to lose travel in the little arm that slides back and forth. It seems to get worse and worse until finally it dosen't engage anymore. It is definately the motor, as when I replace it, it works fine afterwards.

-Abrams

 

I had my front not lock in this last weekend, really sucks. I do not have any vacuum on the diaphragm. Is that caused by the motor not working? Where is this motor. I am fixing to tear into mine today. Any help would be great

 

Hi, the motor is located on the front of the front axle under a black cover. It is located to the passenger side of the differential. The only thing holding it on it a c-clip. Once you remove that, you can just slide it out.

-Abrams

 

Screw the vacuum disconnect! The 4x4 Posi Lok is a good low buck upgrade. But if you're willing to spend some doe, what you really need are 1-piece inner axle shafts inside the housing to bypass the vacuum disconnect motor, a locker, and manual locking hubs. If you have the manual shift transfer case from the factory, you're lucky. If you don't, the electronic 4WD transfer case engagement will be the next thing that malfunctions.

 

eazye727,

The front axle does not lend itself to adding manual locking hubs. The design is simular to a front wheel drive car.

JMC

 

eazye727-

Have you heard of anyone that actually makes the one-piece inner axleshafts? Those would be pretty cool.

-Abrams

 

A simple solution would be to engage it and bolt the lever in that position. Now that will cause the front drive shaft to continiously turn so expect your milage to go down.

JMC

 

Actually, the Zip-Ties with the metal inserts are pretty indestructible. It sounds hokey, I know. But works really good.

The whole vaccuum deal for engaging an axle seems like a pretty crappy design to start with.

-Abrams

 

Abrams,

I find it increable that you are going through so many vacuum motors. There has to be something else happening to them for them to go bad. Could the mounting point be off a tad and it wears out the shaft in the motor. After a while the amount of vacuum applied is not enough to over come the friction casued by the improper wear?

JMC

 

Ditto... JMC hit it on the head.... I've got to wonder if there's something else wrong there.... Have you tried replacing the vacuum lines? Or how about swapping the lines on the solenoids... maybe one of them is sticking, or not closing all the way when it's engaged? (That's actually quite common... the "disengage" solenoid will stick in the open position so when you engage the front end, both solenoids have vacuum on them and the motor never moves)

And I would have to disagree with you... locking hubs are a PITA, no more reliable than CV shafts, and never locked when you need them.

What I'd like to know is that they claim they use the CAD on the 150 to save fuel mileage... what's on the Expeditions? They have the auto 4wd on the Eddie Bauers, and the same front end, but no CAD. Otherwise the auto 4wd wouldn't work in a timely manner... couldn't you just swap out the front axle from an Expy and make it work? Might need a slightly different front driveshaft, but those are cheap....

I dunno... just my 2 cents.