Hubs not disengaging

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Jan 23, 2021 | 04:43 PM

Dweber85rc

Thread Starter

Fleet Mechanic

Joined: Mar 2019

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Hubs not disengaging

Before I rebuilt my front axles this summer and replaced all the hub seals I had disconnected the vacuum lines at the ESOF solenoid since they leaked and I would have to manually lock the hubs anyways. Today I decided to give it a try since I hadn't tried and hooked it back up. The hubs locked instantly but would not unlock without releasing vacuum. I drove a couple of miles, backed up a while and they stayed locked until I disconnected the vacuum line at the solenoid and they unlocked instantly. I did some searching and this would lead me to believe that the vacuum solenoid on the passenger fender is probably not working right. Does that sound about right? All the hub seals are new and since they locked I think I can assume that there are no vacuum leaks so about all it could be would be the solenoid I would think?

Jan 23, 2021 | 05:36 PM

Vinny G-the EX man

More Turbo

Joined: May 2015

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From: Staten Island, NY

Probably the problem, they crack on the bottom of the switch. I changed mine for 35 bucks That switch also controls the air flow in the vents, mine worked intermittently until I replaced it

Jan 23, 2021 | 10:23 PM

DSMMH

Fleet Mechanic

Joined: Jun 2006

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Here is how to check the ESOF solenoid. At the ESOF solenoid, disconnect the vacuum line that goes to the hubs. Connect a vacuum gage where you disconnected the hub vacuum line. Start the engine. You should be able to select 4WD on the dash switch and you should see vacuum. Deselect the 4WD and the gage should go to zero. If not, the solenoid is sticking and needs to be replaced.

Ed

Jan 24, 2021 | 06:06 AM

DavenTn

Cargo Master

Joined: Jun 2013

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From: Florida and Tennessee

The solenoid has a small foam filter in it that deteriorates and gets clogged. It's really not worth fixing since they're pretty cheap... but just in case.

Jan 24, 2021 | 12:52 PM

Teal69

New User

Joined: Jan 2021

Posts: 23

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From: South of Denver

Quote:

Originally Posted by DSMMH

To add to what Ed said, the solenoid (PVHS or Pulsed Vacuum Hublock Solenoid) acts like a click type pen, one click to engage and another to disengage.

A while back I copied this from a thread somewhere.
You can verify the function of the PVHS by connecting a vacuum gauge to the vacuum line from the PVHS which goes down to the hubs behind the passenger side inner fender. Leave the line to the hubs disconnected for the test. (I connect at the factory splice which is right beside the vacuum reservoir.) When you turn the switch to 4HI you will see full vacuum for 30-45 seconds. When you switch it back to 2WD you will see reduced vacuum (about 7 in/hg) for a slightly longer period of time.

Jan 24, 2021 | 04:36 PM

2002Ex

Tuned

Joined: Sep 2019

Posts: 418

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From: Tacoma, WA

My solenoid was shot too. Even the heater controls are affected by it, if you have the push button control style. Replaced mine and the heater controls are good, but my hubs still won't engage from the switch, the transfer case switch works, but not the vac lines. I assume it is the hub seals.

The solenoid is cheap and easy to replace. RockAuto for example.

Jan 24, 2021 | 04:45 PM

Teal69

New User

Joined: Jan 2021

Posts: 23

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From: South of Denver

Quote:

Originally Posted by DSMMH

To add to what Ed said, the solenoid (PVHS or Pulsed Vacuum Hublock Solenoid) acts like a click type pen. One click to engage and one click to disengage.

You can verify the function of the PVHS by connecting a vacuum gauge to the vacuum line from the PVHS which goes down to the hubs behind the passenger side inner fender. Leave the line to the hubs disconnected for the test. (I connect at the factory splice which is right beside the vacuum reservoir.) When you turn the switch to 4HI you will see full vacuum for 30-45 seconds. When you switch it back to 2WD you will see reduced vacuum (about 7 in/hg) for a slightly longer period of time.