4x4 issue - Ford Powerstroke Diesel Forum
 
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post #1 of 5 Old 02-21-2013, 12:05 PM Thread Starter
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4x4 issue

I read the previous 4x4 issue post but mine is a little different. We are in the middle of a snow storm. I always put my 4x4 in from a stop and then goose the throttle to pop it into 4x4. It will run fine but it seems a lot of times when I come to a stop again it will disengage the 4x4 but my dash light stays on. I can switch it back out of 4x4 then turn it right back on then it will engage. Does anyone have any ideas?
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post #2 of 5 Old 02-21-2013, 02:50 PM
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How do you know it is disengaging? Have you checked the hubs, specifically the vacuum tubes and system? It may only be the front hubs disengaging. Also, remember the fronts are not limited slip or locked.

Your technique to engage the 4x4 synchro is very hard on the TC. You should only have to move forward or aft a few feet to engage. You could try to replace the fluid to make it work better, but if you don't exercise the system frequently, it will get sticky over the years. I don't believe you have an electrical solenoid problem.

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post #3 of 5 Old 02-21-2013, 04:07 PM Thread Starter
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I know its disengaging because I can be clicking along just fine in the snow. Then stop at a light then cant get going without the rear kicking out. Then i turn switch to off then back on then I can get going no problem at all. How do I check the vacuum tubes?
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post #4 of 5 Old 02-22-2013, 02:54 PM
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The tubes attach to the back of the front hubs. You might be able to see the deterioration of the hoses, but it could be anywhere back up to and including the vacuum pump. To check the hubs you need to hook up a vacuum source and see if it bleeds off. Of course, there may be other causes like wiring or switches.

With the hublocks in the AUTO position, the 4WD ESOF system uses timed vacuum sequences to lock and unlock the wheel ends when switching the
instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm [8.75 in] Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the
spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including
the 4X4 control module, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring
connections, loose vacuum connections or damaged vacuum lines.

This where I would start with your problem. To see how it all works, raise the front axle off the ground and run vacuum checks to lock and unlock your hubs.

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post #5 of 5 Old 02-22-2013, 03:06 PM
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if the hubs are locking it doesn't require a maintained Vacuum to keep them locked

so if your hubs are indeed unlocking you have a hub issue or maybe a bad ESOF solenoid that is leaking vacuum sending a false unlock signal

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