Am I stuck in 4-high?

[whoisbigman]

So I was under the truck today and was looking around checking boots and things and I tried to turn a drive axle... it wouldn't turn. So I grabbed the front drive shaft and it wouldn't turn. They would only move about a 1/2 inch or something and then clunk, like the front hubs were locked. I had just driven the truck an hour earlier so I wouldn't think vacuum would have leaked down but I started the truck and listened for anything to engage/disengage in the hubs and nothing... still couldn't turn driveshaft.

As I understand it from other posts, the hubs and trans case disengage with vacuum, and if no vacuum, hubs are in locked position. But when truck is running, I should have vacuum and hubs should be free as long as switch is in 2.

Soooooo... what gives?

 

[whoisbigman]

More info...

So after posting, I went out and pulled vacuum line off of actuator by brake master. Pulled 20 lbs on line and it held vacuum. Started truck and actuator was pulling about 24 lbs vacuum. Switched to 4-hi and actuator stopped pulling vacuum. Switched back to 2 and actuator pulled vacuum again. This all seems normal right? So why wont my shaft and axles turn?

 

[Squatting Dog]

What I would do is left a front wheel and see if it spins freely. You should not be able to freely turn the axle by hand. The reason is you will have to turn the prop shaft/diff/and opposite axle since all of those components are locked together. The Vacuum locking hubs (IWE) only lock wheel to axle and the transfer case solenoid couples prop shaft to transfer case.



-Greg (aka Squatting Dog)

 

[whoisbigman]

Got that...

Got that... but driveshaft and axle should be able to freely spin if they are not locked to either the t-case or to the wheels, and when selector is on 2-wheel drive, that should be the case... so what's causing my hubs to be locked?

 

[Squatting Dog]

The ONLY way to check is to block the rear wheels, set the parking brake. Raise one front wheel with floor jack, start the truck, and then turn the tire by hand. If the truck is in 2wd and the axle turns with the wheel. You have an issue with vacuum hub system. If either hub vacuum lines has a small leak it will cause BOTH hubs to be partially engaged.
Remove vacuum lines from IWE, use a hand operated vacuum pump. Repeat turning the tire, if axle still turns that IWE needs to be replaced. If the axle does not turn with tire check others side of vehicle.
If both hubs unlock with hand pump and not trucks vacuum then check IWE solenoid mounted on firewall.

Unless you have the forearms of Popeye you will not be able to turn CV shaft by hand.

-Greg (aka Squatting Dog)

 

[whoisbigman]

Thanks... I will do that this afternoon. This is my first Raptor but I have had and built many 4-wheel drive trucks. Since I'm not yet familiar with how this system works, I'm trying what always worked in the past. On a superduty for instance, vacuum actuates hubs into 4-wheel drive... this almost seems counterintuitive, but I get it.

Getting out the jack... and my forearms are strong enough to lift the truck let alone twist an axle

 

[Squatting Dog]

Ford claims that it is designed feature so you do not get stuck without 4wd. The system defaults to hubs locked.. The issue is during slow leak down or over night the locking ring is not fully engaged. This causes wear of the rings and then during off road use causes them to slip and eventually break.

I am happy to help.. This system is the bane of my existence.


Here is a decent thread (one of many) about the ****** system
http://www.fordraptorforum.com/showthread.php?t=20474


-Greg (aka Squatting Dog)

 

[whoisbigman]

Okay then... so here goes. Jacked up pass side front tire, wheel wont turn, hubs are locked, I'm in 2-wheel drive. Push key fob thingy to start truck while underneath, still no turny with truck running. Shut off truck, get vacuum, pull 25 lbs vacuum, tire spins, able to turn axles by hand (told you I was strong enough) everything doing what it's supposed to do. Leave vacuum on and vacuum holds. check to see if actuator is pulling vacuum, it is pulling 24 lbs. I reattach line to actuator and wheel is locked again because vacuum escaped when I took my hand pump off. Sitting next to tire, start truck with remote thingy, wheel wont turn...

Wait for it...

put key in ignition and tire spins freely, axles and shaft turn freely.

Lesson we have learned is that remote key fob thingy starts engine only, doesn't turn on other systems like vacuum pump. As soon as key goes in, everything works.

I bet everyone knew that but me.

---------- Post added at 05:54 PM ---------- Previous post was at 05:53 PM ----------

Thank you again for your help. You will see me around here a lot.

 

[Squatting Dog]

There is no vacuum pump. You are correct the BCM/PTCM does not turn on. Which means there is no signal to the IWE solenoid mounted on firewall to open and use engine vacuum. Thank you. I learned something new about the BS vacuum system.

-Greg (aka Squatting Dog)

 

[PropDr]

Me too...


Thanks!