New to board and looking for help. I have a 2015 F-150 I bought used with 100K miles. Truck runs great except when I take on beach and run in 4WD. While running in 4WD under load in soft sand, 4WD makes terrible banging sound and shakes the whole front end. This bang happens randomly but many times while driving. I am under warranty and have taken to Ford and provided videos documenting sound but they cannot replicate the issue on pavement or in the shop. Again, it only happens when 4WD is under load or stress. Oddly enough, if I run in reverse in 4WD on the beach in the same soft sand there are no issues at all. I have driven in reverse for long distance on beach and the bang doesn't happen.

IWE and and half shafts were just recently factory replaced. Ford dealer is at a loss as to what the problem is and having trouble diagnosing.

Attached is short video of the sound while running on the beach.

Any help or ideas would be appreciated!

Thanks.

 

When does the noise happen, at the same moment the shift to 4x4 completes?

Are your tires all matching, age and style?

 

Welcome!
.
s.
As a newbie...
..

 

Noise happens randomly when driving and 4WD is underload/stress. If I am running in compact sand trail leading to beach it dies not happen, only when sand gets a little deeper, Noise/bang does not coincide with shifting into 4WD.

All tires match and are less than 1 year old. 33" BFG KO2s.

Again, this problem does not exist when running in reverse in deep sand so I don't think it is a tire issue.

 

As far as I know condition of front end suspension and alignment is fine. Truck has been serviced by dealer numerous times and nothing brought to my attention.

Truck does have 2" spacer level kit in front and I have added 33" BFG KO2s.

 

Had a similar issue with my 2012 f150 last winter, I would get a loud bang while in 4wd when under a load. I ended having a new transfer case installed in my truck. That took care of the issue.

 

It sounds like the chain in the transfer case is stretched and is slipping when under load. That is what happens when you drive in 4X4 while on road surfaces with good traction. There are a lot of people who come on these forums and will tell you it is OK to drive in 4X4 on pavement. It is not. BTDT and paid the bill to have transfer case rebuilt.

The damage is cumulative and it doesn't break all at once. But parts wear out gradually. Often, as in your case, it is the next owner who gets to pay the bill.

You can see the internals here. When the driveline is under stress something has to give. Sometimes parts break, sometimes they stretch. Once the chain stretches it will start to slip over the cogs when under a load.

photo of transfer case - Bing images

 

I'm going to say that even though the sand is soft the tires are not turning at the same speed. One or more tires are getting the grip and other(s) are spinning. Similar to trying to turn on dry pavement.

 

Deleted comment. Should have listened to vidio befoer commenting.

 

Definitely transfer case as stated by Cliff85 and marshallr.