Thump heard around 40MPH, only while in 4A

[Dustin Gebhardt]

I need some pointers on where to start looking. I have a 2007 EL Limited 4x4. Recently, I've been hearing and feeling a thump at around 35-42MPH. This hasn't been a normal transmission gear shift, but rather in-between shifts. I can eliminate the noise if I switch from 4A to 2H. If I accelerate gingerly, the noise doesn't happen (or it's so faint that I can't otherwise hear it), but if I accelerate moderately or faster, the noise happens every time. Since this noise only happens in 4A, I'm guessing that it has something to do with the components in the front drivetrain.

I suppose that if I knew exactly what is different while running between 2H and 4A, then I could troubleshoot the issue better. Is the transfer case turning the front driveshaft while in 4H (but the wheel hub are unlocked), but not turning the front driveshaft while in 2H? Or are the wheel hubs locked but the transfer case is disengaged?

Any thoughts?

 

[1955moose]

Check the IWE actuators, and vacuum going to them. Theirs videos online that walk you through it. Common problem on F150/Expedition. Also check trans fluid for proper level, cleanness. Lastly I'd run a codes check, see if anything pops up.

Sent from my N9131 using Tapatalk

 

[gixer2000]

Check the IWE actuators, and vacuum going to them. Theirs videos online that walk you through it. Common problem on F150/Expedition. Also check trans fluid for proper level, cleanness. Lastly I'd run a codes check, see if anything pops up.

Sent from my N9131 using Tapatalk

I'll second having a look at the IWE hubs and components. They are vacuum controlled so quick throttle whould have a big impact on vacuum. The solenoids a pretty common to split and leak. I actually did mine in my 07 last winter. Also I recently did the IWE's and the check valve in by the solenoid just as preventive maintenance.

In 4A the hubs lock but transfer case is disengaged. The hubs lock by removing vacuum and unlock when vacuum is applied

 

[chuck s]

Curious why you're running in 4A for normal driving.

-- Chuck

 

[Dustin Gebhardt]

Curious why you're running in 4A for normal driving.

-- Chuck

Why not? It's "safer" than running in 2H, if an emergency situation was to come up. I ran in 2H for several months to evaluate the impact it has on gas mileage and it was unnoticeable. The Ford manual says that 4A can be run in dry weather and on pavement.

 

[chuck s]

Not sure it's safer. Ain't gonna stop any quicker. Ford says 2H and 4A are appropriate for all driving. But it does run at least some power to the front axle all the time according to the little power distribution graphic on my '17 dash in the "off road" display section. On my '07 like yours I could feel the added mechanical drag with it was activated.

Since you can eliminate this in 2H I suspect the bump is related to the truck trying to put some power to the front axle and perhaps taking up the slack in the system.

Interesting my earlier Explorer always ran in 4A unless switched to 4H or 4L, there was no 2H.

-- Chuck

 

[JExpedition07]

Not sure it's safer. Ain't gonna stop any quicker. Ford says 2H and 4A are appropriate for all driving. But it does run at least some power to the front axle all the time according to the little power distribution graphic on my '17 dash in the "off road" display section. On my '07 like yours I could feel the added mechanical drag with it was activated.

Since you can eliminate this in 2H I suspect the bump is related to the truck trying to put some power to the front axle and perhaps taking up the slack in the system.

Interesting my earlier Explorer always ran in 4A unless switched to 4H or 4L, there was no 2H.

-- Chuck

The Explorers used a center differential disconnect no vacuum system, therefore the front half shafts always spin but the diff is not engaged. Different setup on the expy as it uses a vacuum hub system. The 4WD systems are not the same on 07-14’ vehicles and 15-17’ vehicles, we’ve seen this recently. Many different vacuum parts and likely different IWE’s and T-Case. The 07-14’ Expedition uses ControlTrac 4WD and in the 4A mode is 2WD bias until slip is detected. Ford says it’s safe to use on pavement as power isn’t sent to the front wheels until needed. Could be different on yours as it’s a 2017.

 

[JExpedition07]

OP it sounds to me like an IWE may be worn out. Your symptoms are kind of backwards of what is typical, normally they grind in 2WD when they lose vacuum and half engage. Since you say the grinding happens in 4A and stops in 2H when vacuum is applied I’d lean toward warn teeth on a IWE possibly. In 4A your hubs are engaged to the shafts and turn with the diff, the T-Case does not spin until needed to answer your question.