4x4 Issues
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Tuned
Joined: Mar 2005
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From: Mesa AZ
4x4 Issues
Ive got a 2003 expedition with some 4x4 issues. Issues started over a year ago. I had a strange noise I could not narrow down. It sounded like a bearing lacking lube . I poked, prodded, spun, & shook everything I could think of. The sound only showed up on the freeway under hard acceleration. I realized a few months ago what it was. The right front 4x4 actuator is trying to engage under low vacuum conditions. (hard accel) I changed a bunch of really poor looking vacuum connections today and tested it. No change. The noise goes away when put in 2 hi. When put in awd, both hubs just chatter.
I havent had a chance to vacuum check anything with a mity vac, but looking closer at things, Im not sure what to even check. The hubs have a large vacuum line and a small vacuum line going to them. The large line ties into the vacuum system and the small one goes no where. It comes back up into the engine bay and is open. Both sides are like this. Am i missing something here?
Tried 4 low today and it does nothing. Does not lite the 4 low light on the dash and no engagement at the transfer case. When the transfer case motor is bad, does the 4x4 low light still illuminate?
Thanks for any help.
I havent had a chance to vacuum check anything with a mity vac, but looking closer at things, Im not sure what to even check. The hubs have a large vacuum line and a small vacuum line going to them. The large line ties into the vacuum system and the small one goes no where. It comes back up into the engine bay and is open. Both sides are like this. Am i missing something here?
Tried 4 low today and it does nothing. Does not lite the 4 low light on the dash and no engagement at the transfer case. When the transfer case motor is bad, does the 4x4 low light still illuminate?
Thanks for any help.
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Joined: Dec 2014
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You can find the owners manual in a downloadable PDF here:
https://owner.ford.com/tools/account...ord/Expedition
https://owner.ford.com/tools/account...ord/Expedition
Fleet Owner
Joined: Apr 2008
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First things first, vacuum test everything. It only take one leak or one plugged line to gum up the works. That small line is an air vent. When the hubs get release and the vacuum actuators move back, those little hoses let the air back in. The shift motor controls the dash lights. So the low light will not light if the t-case/shift motor isn't shifting into low.
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Tuned
Joined: Mar 2005
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From: Mesa AZ
Ok, I'll vacuum check them when I get home today. I'm thinking I may not have been able to get 4 low to work because I never shifted to neutral. I'll give that a try. Any idea why the hubs lock in 4x4 but just chatter in a4wd?
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Tuned
Joined: Mar 2005
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From: Mesa AZ
Ok, finally got a chance to mess with it. happy to report that it does shift into 4low when done properly. 
I started with vacuum testing up at the selector valve behind the battery. The system would not hold vacuum. went to the passenger side hub and tested at the actuator. With my pump on the bigger of the two nipples, it holds vacuum. Went to the passenger side and it will only hold vacuum when i plug the smaller of the two ports while pumping.
The passenger side is the one making the noise. I am still kinda unsure which side is bad. Is the smaller tube simply a vent on the back side of the actuator diaphragm to allow air in when under vacuum and to let it back out when vacuum is released? That would make sense to me. Only thing throwing me off on that theory is the fact that the side that does hold vacuum is the one that seems to be making noise.
I started with vacuum testing up at the selector valve behind the battery. The system would not hold vacuum. went to the passenger side hub and tested at the actuator. With my pump on the bigger of the two nipples, it holds vacuum. Went to the passenger side and it will only hold vacuum when i plug the smaller of the two ports while pumping.
The passenger side is the one making the noise. I am still kinda unsure which side is bad. Is the smaller tube simply a vent on the back side of the actuator diaphragm to allow air in when under vacuum and to let it back out when vacuum is released? That would make sense to me. Only thing throwing me off on that theory is the fact that the side that does hold vacuum is the one that seems to be making noise.
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Tuned
Joined: Mar 2005
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From: Mesa AZ
Stumbled upon this article from a google search.https://www.ford-trucks.com/forums/8...then-some.html
Pretty much sums it up. I definitely have one actuator with a bad diaphragm and possibly a damaged one on the other side.
Pretty much sums it up. I definitely have one actuator with a bad diaphragm and possibly a damaged one on the other side.
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Fleet Owner
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Because it's trying to engage but there isn't enough vacuum to pull it all the way in. The other side with the bad diaphragm is not moving at all.
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Tuned
Joined: Mar 2005
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From: Mesa AZ
Happy to report , it is fixed. Unfortunately, as I expected , I had to replace the passenger side as well. The diaphragm was in tact , but it was my source of grinding. Thanks for all the help.
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