Let's play "What's that Noise?"

[acfortier]

I've got a pretty loud oscillating higher-pitched sound that seems like it's coming from the transmission when I'm driving in the cab. I feel like it goes away after awhile, but not always. It's kinda annoying at this point, and driving me insane. Can anyone else identify/hear it in these videos?

 

https://drive.google.com/file/d/1NQ2llMEPGLJLTITn_kyvNMR_POcEnwDO/view?usp=sharing

https://drive.google.com/file/d/1J_u6DNNMJuUnMqDREZqTyUlWXnD-BXV-/view?usp=drive_link

[Strokermjcomanche]

Does the noise match the speed that you’re going? In other words does it go faster as you go faster, or slower as you go slower? Without being close to it, I would say something internal. 
 

However maybe u joints, or throw out bearing are a couple other things I can think of off the top my head

[pizzaman09]

Start with the easy things I'd say, check that nothing is rubbing on the drive shafts and confirm the fluid levels are correct in the transmission and transfer case.  

 

I kind of agree that the sound could be a worn out throw out bearing, but the sound should change when you push in the clutch.

[acfortier]

Forgot to follow up. No, I don’t really notice the frequency of the noise change when I go faster—it might get louder but that’s it. Seems to go away under ~20 mph or so?

 

Haven’t noticed if it goes away when pushing the clutch in, I’ll give that a shot.

 

Ill take a peek underneath and check fluid levels.

[acfortier]

Changed fluid and put in MT90. Noise is still present when cold, but goes away much quicker and doesn’t get nearly as loud as it used to.

 

Noise does not go away when clutch is pressed in.