thanks for the comments...definitely not a tire/gravel issue as we just did a rotation.

The sound reminded me of when we were kids and used a clothes pin to hold a baseball card on a bicycle wheel to make it sound like a motorcycle. Flap flap noise that increases with speed, with or without brakes or 4x4 in use.

It started after using cruise control in the steep mountains in Pennsylvania. When going downhill, the cruise makes the vehicle slow down by gearing down. Coincidence or could this have caused my issue? Any opinions on using cruise control on steep hills vs braking for long periods going downhill? Is this ok or did this f-up my truck?

 

This is completely okay, just the same as using "M" mode to manually downshift the transmission. You didn't hurt a thing.

 

What someone (the dealer?) needs to do is put the truck up on a frame lift, start it up put it in 4-High and walk around underneath it with all four wheels turning under power. It shouldn't be too hard to determine where the noise is coming from.

 

I like the thinking there, but there might be a issue there. Since all 4 wheels would be off of the ground, there would be no load on the engine or rest of the drive train. In most cases with dealing with differential and other like components, they can act very differently with load and without. I hope that made sense...havent had my coffee yet.

 

I Would think you would need the truck under Load to find the noise How about a Dynamometer that would put the truck under a Load that shouldn't cost to much to do that. Again just a thought?

 

Well, if the truck is still under warranty, hand the dealer the keys and tell him to call when its fixed. Who cares how many parts he replaces. He'll have to explain to Ford why it took $5000 worth of parts and 80 hours labor to fix a clicking noise.

On the other hand, if its not under warranty, anything that you can do to narrow the problem down will save you money in the end. Since I doubt any shop would allow you to do this (insurance issues!) you'll have to try this in your driveway - get the truck up on 4 jack stands. Fire it up in 4-High and have someone sit in the truck. Give it a LITTLE gas and ride the brakes to load the drive-train. If you're hearing the noise while just cruising down the street, you really don't need a lot of load on the drive-train to make it click. If it is a problem in the braking system it should make the noise before you ever touch the brake pedal.

I don't know of any shop with a 4 wheel dyno that will run your truck for cheap.

 

Why are we all trying to diagnose an issue that the dealer is about to fix? I think this part has been done.

 

Dealer's current thinking is the front differential bearing & we are awaiting the part.

What causes this to fail at <20,000mi.? Defective part? Went dry? Improperly installed at factory?

Will changing this lead to anymore fun failures down the road?

 

Hard to say what the reason is. I'll tell you that I've had vehicles that have never had a bearing failure, and I've had a couple that have had one or two. To some extent it's dependent on the skill of the technician.

 

Someone said they don’t click... had a cousins Nissan pickup back in the day ( probably about ‘89-‘90 ) that was in fact emitting a clicking sound right before it locked up thought that truck was gonna flip over forward

 

Bearings are mass produced and a certain, very small percentage will be defective. You just happened to be the lucky winner.

 

There was a thread about this a couple years ago. The guy wound up having the front differential changed under warranty. The pinion was set up wrong. This should cause no further issues once fixed.

 

 

As was mentioned earlier in this thread, if the front wheel hubs are disengaged and the transfer case if in 2 wheel drive the front differential should not be turning. So how can it be the issue?

 

good point, I will ask the tech when I pick up the vehicle.