I sure would appreciate someone posting an assembly scan of one of the front vacuum operated hubs on our '04 and '05 4x4's. Just curious as to how these things work and how reliable they are. I've had manual locking and mechanical auto locking (didn't particularly like the latter type) hubs on my other 4x4's.

Thanks,

Scott

 

guaranteed to not last as long as manual hubs.

 

One thing interesting about these hubs is that they are excercised plenty.

The vacuum from the engine "unlocks" them.

So you start your engine, they disconnect.

Stop your engine, they engauge.

-James-

 

That is interesting! I would hope that if one of the vacuum lines broke, the hub would be locked instead of the other way around

Thanks,

Scott

 

Are you sure its not the other way around. What's your source for this info.

 

Vacuum locks the hubs, this is a failsafe. If for some reason you should lose vacuum then your not stuck with the hubs in the locked position.

My '69 T-bird has a similar thing for the headlight covers. If the vacuum fails then the covers are forced open so you can still use the lights.

 

TBird, you got the million dollar question wrong....

Zman... here is the "source for that info".

Normal Operation
The 4x4 module energizes the IWE solenoid which applies vacuum to the integrated wheel-ends disengaging the front hubs from the front axle and driveshaft. If the solenoid is not energized, an internal spring keeps the hubs engaged. Systematically check the necessary inputs and outputs at the 4x4 module, internal components of the transfer case and shift lever, IWE components, and drive axles.

 

There's still vacuum involved in there somewhere though right? My head hurts!

 

yea normally locked. then when truck is started it applys vacum then it's unlocked. I'm trying to replace my second one right now. the reason they are engaged and disengaged at the hu instead of in the differential is it saves .5mpg according to the shop manual.

 

You can test this out pretty easily also. If you ever have the front of the truck off the ground or on a lift, try to spin the front wheels with the truck off. They will be locked to the driveshafts, with truck running they will not (unless in 4WD of course). This also makes me realize something else.....There is no way for someone to tow a 4x4 F150 by just lifting the rear wheels, it would have to be flatbedded.

EDIT: And if you are in 2WD and if the vacuum line were to break or solenoid to F up, the hubs would lock up.......BUT the transfer case will not be engaged so the front wheels won't be locked to the rear.

 

I believe that the clutch in the transfer case is unlocked then the truck is parked. So you should be able to tow it, although the drive shaft would turn.

 

Owners manual says not to tow 4WD trucks. They should be put on a flat bed to be transported.

 

Someone stealing the truck probably won't read the manual first. Actually, Ford uses sensors on the mustang anti-theft package to stop this method of theft.

 

Because the axles are not rotating, reducing the rotating mass.

 

i thought if you put the transfer case in the N position, neither the front or rear shaft will turn, alowing you to tow the vehicle...atleast that was the way it was on my jeep