Whistle in 4WD?

This weekend I put the truck into 4WD, rolled the windows down, and cruised down a dirt road. While driving I noticed a really loud steady whistle. At first I though I had gotten a rock stuck in a brake caliper or something. It didn't go away. Stopped and drove in reverse a couple times in case I had a brake drum stuck or something.

Ultimately I determined that the whistle is ONLY present while in 4WD. The instant 2WD engages the whistle stops. If I put it back into 4WD the whistle begins within 2-3 seconds and won't stop while the truck is moving unless I drop back to 2WD.

Reaching out to my Toyota dealer since the truck is still under 60k miles. Curious if anyone has experience this or has ideas on what should be checked out.

Front Diff had fluid change at 30k miles. Truck is now at 46k miles. Transfer case is probably due for refill though (still factory fluids).

 

How fast were you going?

 

20mph at the most.

 

Could it be the add actuator? Are you able to hear it while in park and still in 4wd?

 

Only whistles while in motion.

 

It’s the ladies whistling as you go by.

 

Ha! Doubt it.

Taking it to Toyota tomorrow...

 

Of course... Toyota says they cannot replicate the whistling noise...

Figures. Whistled like a S.O.A.B. this weekend.

 

Did you ever get to the bottom of the whistling? I just checked out a used 2014 4x4 today with 96k that seemed to have the exact same noise you’ve described.

 

It went away on its own. I think maybe something got struck in the brake caliper or something. Really not sure.

 

Anyone have any insight? Been trying to diagnose this issue on my truck