Headed into the Dealer for Work

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JExpedition07

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Update

They just got to it even tho they've had it since Tuesday. They were unable to recreate the problem so I had to go in and do it for them. But the tech riding with me was immediately pretty sure he knew what the problem was once I recreated it...good news: not the transmission.

It sounds to him like there's a failure in the 4wd vacuum system. Apparently the hubs default to 4wd as that's seen as more useful (if the system fails they want it to default to 4wd in case you're stuck somewhere). So in 2wd the vehicles run a vacuum to hold 2wd. It sounds to him like the system is leaking somewhere so it's losing the vacuum and the hub on the front driver's side wheel is trying to engage. That's the scraping/grinding noise I'm hearing, the hub attempting to engage while moving. The system isn't showing 4wd because the transfer case is still in 2wd, it's just that individual hub trying to engage because the vacuum that holds it in 2wd is failing/failed.

So, they have to tear into the 4wd system and see where the vacuum is bleeding off, fix that, and I should be ship-shape.

Annoying, but reassuring it's not something more serious like the transmission.

I know there are some seriously mechanically-minded folks on here...if that scenario sounds reasonable, please let me know. If that sounds like hogwash, that would also be helpful to know.

I’m skeptical. I’ve worked on the vacuum hub system, my 2007 has the same setup. Most fords from the early 2000s till now use this setup so we know them pretty well at this point. It is true when a hub is half engaged half not it will grind. Normally it is at random and upon turning etc. But what concerns me is you say it is specifically in 2 and 3 gears and now shifting to reverse. They will not grind unless they are spinning as well does it grind in reverse right away upon shifting?

There is a 4WD solenoid that vents vacuum to atmosphere on our trucks when they are shut off. (When off the hubs lock due to lack of vacuum). Upon startup the hubs disengage when vacuum is present, in 4A however the Solonoid will vent vacuum and hubs will engage so that the front axle is on standby when power is sent forward.
It’s plausible yet this isn’t how the system normally fails as you describe your issue. The system will grind if an actuator is not engaging the with the hub completely, this is often caused by a seal failure in the hub actuator. My main questions are these:

Is it specifically at the gearshift s you mention?

Are you rolling in reverse when you experience the grinding or is it upon shifting?

If your answers are that it’s when rolling and Not specifically at gearshifts then it is very possible. Please view the attached:

 
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aggiegrad05

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I’m skeptical. I’ve worked on the vacuum hub system, my 2007 has the same setup. Most fords from the late 90s till now use this setup so we know them pretty well. It is true when a hub is half engaged half not it will grind. Normally it is at random and upon turning etc. But what concerns me is you say it is specifically in 2 and 3 gears and now shifting to reverse. They will not grind unless they are spinning as well does it grind in reverse right away upon shifting?

There is a 4WD solenoid that vents vacuum to atmosphere on our trucks when they are shut off. (When off the hubs lock due to lack of vacuum). Upon startup the hubs disengage when vacuum is present, in 4A however the Solonoid will vent vacuum and hubs will engage so that the front axle is on standby when power is sent forward.
It’s plausible yet I’m skeptical, this isn’t how the system normally fails as you describe your issue.

I was thinking about the fact that it only seems to do it on shifting. Maybe what is happening is it will start to grind at the tall end of whatever gear I happen to be in and then clunk in when it shifts because the power stops for a split second to accommodate the shift. I FEEL like it’s happening on the shift but to be honest it scrapes as its climbing and then clunks when it shifts. I assumed a shifting problem but maybe not.

The issue happened in reverse one time when I was a little quick on the gas after shifting into reverse. With all that was going on I assumed it was related, but perhaps it was just a coincidence and I just got a little ahead of the transmission.

I have a video of my dash while it’s “performing” so you can hear the noise and see what the gears are doing, but I can’t figure out how to post a video on here.
 

deweysmith

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A grinding/ratcheting sound wouldn't really come from the transmission if the vehicle still moves. All gears are fully meshed 100% of the time in an automatic. You can get a ratcheting sound if you drop it in Park while the drivetrain is still moving, the Park pawl can ratchet a few times if the transmission is spinning too fast. If it's really a ratcheting/grinding sound and you can still drive it at all, it's very very unlikely that it's the transmission.
 

JExpedition07

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I was thinking about the fact that it only seems to do it on shifting. Maybe what is happening is it will start to grind at the tall end of whatever gear I happen to be in and then clunk in when it shifts because the power stops for a split second to accommodate the shift. I FEEL like it’s happening on the shift but to be honest it scrapes as its climbing and then clunks when it shifts. I assumed a shifting problem but maybe not.

The issue happened in reverse one time when I was a little quick on the gas after shifting into reverse. With all that was going on I assumed it was related, but perhaps it was just a coincidence and I just got a little ahead of the transmission.

I have a video of my dash while it’s “performing” so you can hear the noise and see what the gears are doing, but I can’t figure out how to post a video on here.

A video would be great if you can post it. Your answer makes it seem like a good possibility that the hub actuator up there is grinding teeth with with the hub due to a loss of vacuum. This is most likely a bad seal in the assembly at the wheel itself that’s normally when they are half stuck engaged.
 
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aggiegrad05

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A video would be great if you can post it. Your answer makes it seem like a good possibility that the hub actuator up there is grinding teeth with with the hub due to a loss of vacuum. This is most likely a bad seal in the assembly at the wheel itself that’s normally when they are half stuck engaged.

I’ll look and see if there’s a way to post a video. I really appreciate the input. I was encouraged at how confident the tech was as soon as he heard it.

They’ve got a week to fix it before the battle wagon is scheduled to take the fam on a road trip.
 

JExpedition07

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Since we have established it doesn’t seem to be drivetrain related and happens more at random I’m guessing a hub actuator on that drivers side front..... my passenger side actuator had to be replaced as it was doing the same thing, the actuator seal failed and it was staying partially engaged (the wonderful grinding you hear is the teeth not meshing all the way and it’s chewing away at the teeth on the hub, never fear the actuator is a softer metal and will take most of the damage). It’s not totally uncommon for them to fail prematurely. Wish you well good luck!
 
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aggiegrad05

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Well, it was fixed for a whole two weeks....until this morning when the same damn thing happened. So back in it goes.
 
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