Auto hubs not engaging

Reply Subscribe

Thread Tools

Search this Thread

Jan 3, 2011 | 09:08 AM

emmagator

Thread Starter

Senior User

Joined: Aug 2006

Posts: 333

Likes: 0

From: Roseburg, Or

Auto hubs not engaging

2006 F350 6.0l. Manual 4wd works fine, but the auto hubs wont lock. I want to say this happened after i got new tires mounted and balanced, not sure though, dont use 4wd much. Anyway is there a vaccuum line that the tire guys might have damaged? Any other suggestions? Thanks

Jan 3, 2011 | 09:12 AM

riverstroker04

Cross-Country

Joined: Jul 2010

Posts: 96

Likes: 1

From: on the river

yep look at the wheel hub on the back there is a ABS wire and a VAC line see if that has been knocked off.

Jan 3, 2011 | 10:34 AM

Got Rattle

New User

Joined: Dec 2004

Posts: 16

Likes: 0

I just went through this with my 05. Turned out to be the vacuum switch mounted on the passenger firewall, right by the vacuum pump. You can easily verify the switch by disconnecting the vacuum line from it and plugging it in directly to the pump. Fire the truck up, let the pump rebuild vacuum, turn the dash switch to 4X4, and move the truck a few feet. Before exiting the truck, turn the wheel all the way to the right and put in park. Now you can reach in behind the wheel and try to spin the drive shaft from the transfer case to the front dif. And you can try to spin the u joints at the end of the front axle.

If the pump is working and the 4X4 is now engaged, then it's probably the vacuum switch under the hood. Took longer to fetch the socket and ratchet, than it did to swap it out.

Hope this helps.

Jan 3, 2011 | 02:59 PM

rpaxton

New User

Joined: Jun 2004

Posts: 19

Likes: 0

From: College Station, TX

Quote:

Originally Posted by emmagator

I'm driving a 2001 truck, and on my system you HAVE TO BE MOVING for the auto hubs to lock. Not sure if the 06s have the same need, but try that before you start ripping your truck apart.

Jan 3, 2011 | 03:08 PM

UGA33

Lead Driver

Joined: Sep 2006

Posts: 5,665

Likes: 164

From: Cartersville, Ga

Quote:

Originally Posted by rpaxton

I'm driving a 2001 truck, and on my system you HAVE TO BE MOVING for the auto hubs to lock. Not sure if the 06s have the same need, but try that before you start ripping your truck apart.

Still works the same way. Tire has to make atleast a revolution before the auto hubs lock. Manually locking them locks them immediately. Test the 4x4 solenoid that was mentioned in the post above. They fail a lot.

Jan 3, 2011 | 07:39 PM

emmagator

Thread Starter

Senior User

Joined: Aug 2006

Posts: 333

Likes: 0

From: Roseburg, Or

Quote:

Originally Posted by rpaxton

I'm driving a 2001 truck, and on my system you HAVE TO BE MOVING for the auto hubs to lock. Not sure if the 06s have the same need, but try that before you start ripping your truck apart.

Tried this, i went forward reverse. They just are not engaging, ill check out what you guys suggested, thanks. Other than solenoid or the lines themselves, is there anything else i should check? Thanks

Jan 4, 2011 | 09:22 AM

spstgermain

Junior User

Joined: May 2010

Posts: 57

Likes: 1

I just repaired mine. Get a vacuum gauge and do the following:

Remove line going to solenoid and check pump. There should be approx 14 inches of vacuum there.

If not pump is bad. If O.K.remove line going to hubs on the solenoid.

There should be approx 14 inches when engaging 4 wheel drive.
It should be there for around 30 secc.

There should be approx 7 inches of vacuum when going back to 2wd.
It should be there for 20 to 30 secs also.

If you don't get the 14 when engaging, as was my case, the vacuum solenoid is bad. I was getting only 7.

If all that is good you have either a leak in one of the lines going to the hubs or a leaking hub itself.

You cannot check system by just disconnecting a hub line and seeing if you have vacuum there.

Fixed mine in less than 1 hour after buying a 20 dollar gauge.