4WD vacuum switch

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Nov 22, 2006 | 01:11 PM

sonicblue2003

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From: Windsor Ontario Canada

4WD vacuum switch

I have had problems with my auto/manual hubs,so I did some research on here and found some interesting stuff. So I have dissasembled them ,cleaned and lubed as explained. Ok so now that that is done I thought I would check the vaccum at the hub. Well there wasn't any when it was running. So I traced everything back to the switch on the RF fender. I put a gage on the port with the supply still hooked up and when I swich into 4WD high or low I get vacuum.
Heres the question I have. How long should the vacuum stay applied to the hubs. Mine quits after about 30 seconds. Does this mean something is wrong with a relay or is this normal??? If you lose vaccum wont the hubs disengage?
I didn't stand there and wait for more than a couple of minutes to see if there would be another pull of vaccum but i need to know what to expect and what to look for.
Thanks in advance.

Nov 22, 2006 | 01:56 PM

biz4two

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Joined: Sep 2003

Posts: 5,844

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From: Albuquerque

Nope your vacuum actuator is performing normally. If you have no vacuum at the hub, then it must be between the hub and the vacuum actuator...IMHO.

The vacuum actuator will provide the initial pulse of vacuum, then it will turn off. It does not continue to provide vacuum to the hub. The hub should lock and remain locked until the ESOF switch is turned to the 2HI position...then again the vacuum actuator sends a pulse to the hub and disengages the hub.

Hope this helps...and makes sense.

biz

Nov 22, 2006 | 04:34 PM

sonicblue2003

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From: Windsor Ontario Canada

Ok. So what you are saying is that it only needs to engage and the plastic thingy (for lack of the correct term) locks and hold it there until it ratchets and allows full return with the next pulse?
The reason I had no vacuum at the hubs is, by the time i got in and out of the truck,it had already shut off. DUH!!! I'm blonde!
Thanks.

Nov 22, 2006 | 05:36 PM

2012 SD Snowbuster

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Joined: Jan 2005

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From: Rochester, NY

I have a similar question.. I slid off the road and switched the selector to 4hi and the truck didnt engage, result rear tires spinning and diggin up the grass. Shifted from reverse to drive, to rock it and still no 4 wheel. The Powerstroke is just diggin some more. I still had no 4wheel after 2 more trys and then just ripped the side of the road up. Once I got back on stable ground I pulled off to the side(gravel) and flipped the switch.. bingo 4 wheel light on dash and no spin...what gives?? I have had 4 other 4x4's and none had this shift on the fly crap switch I had a shifter on the floor. I pulled back and it was in...no maybe it's in I knew it was in.. Can somebody enlighten this oldschool 4x4er?? I love the 04 but hate this ESOF stuff so far.

Nov 22, 2006 | 06:51 PM

LP2

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I couldn't agree more. Give me a part # for the floor lever please!

Nov 22, 2006 | 07:14 PM

sonicblue2003

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Joined: Aug 2005

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From: Windsor Ontario Canada

Also take note for you ESOF guys. When you put the selector in 4HI you get a slow vacuum apply(takes 5 to 10 seconds for full vacuum). But if you put in 4LO you get instant vacuum.whatever amount you have at the manifold.
I guess that is so you don't get a bang when it engages at 50mph.