2004 4.8l Whining/grinding from tranny?

[gpewett]

OK , I have not had this truck long it is a 2004 4.8l auto trans with 190k miles. I have been experiencing a strange whining/grinding randomly while driving. It seems to happen more while decelerating but has even happened when putting the truck into reverse and not moving. If I shift the truck into neutral the noise continues and usually only stops when I press on the gas. This started happening after the front right bearings were replaced and the tranny fluid changed. I suspected the tranny pump was making this noise(even though it seems too loud to be coming from that) . I had a local mechanic pull the pan and said the tranny looked much better then he expected. He replaced the fluid and filter pack. It is still happening. It does not affect speed, rpms, and I can usually make it stop by pressing the gas. I have no idea what is going wrong but it sounds major and two shops have not been able to recreate it. The truck shifts and drives good even while this noise is happening. I am almost positive the sound is coming from right in front of the center console under the truck. I have a video of me driving around 45 mphs. The noise starts as a let the car decelerate on it's own and I can stop it by lightly popping the gas. Any help would be greatly appreciated. Thank you

VIDEO

https://drive.google.com/file/d/1LxRDz8Tw3RvZzeB7OynoJ1KZg5R0h6q7/view?usp=sharing

[ryank1]

Sounds more like a differential coming apart or maybe in the transfer case.  But it shouldn't make a noise when not moving.  

[silveradosid]

look for a broken or loose heat shield

[gpewett]

2 hours ago, ryank1 said:

Sounds more like a differential coming apart or maybe in the transfer case.  But it shouldn't make a noise when not moving.  

It does it a good amount when not moving. Usually in reverse

[gpewett]

1 hour ago, silveradosid said:

look for a broken or loose heat shield

Would it be a heat shield if it does it while sitting still in reverse? I thought the heat shields only made noise when the vehicle was moving and creating vibrations.

[carkhz316]

That definitely sounds like something in the drivetrain, unfortunately. It sounds like someone trying to forcibly shift a manual transmission and the synchros are ratcheting. Fortunately, there's not much inside the transmission that could make that sound, but there's not much else that would be spinning when the truck is stopped.

[gpewett]

12 hours ago, carkhz316 said:

That definitely sounds like something in the drivetrain, unfortunately. It sounds like someone trying to forcibly shift a manual transmission and the synchros are ratcheting. Fortunately, there's not much inside the transmission that could make that sound, but there's not much else that would be spinning when the truck is stopped.

Someone said it sounded like the truck trying to go into 4h. So when it did it again i could feel the shaking in the 4wd shifter. I shifted it into 4h and then pitch changed and then I shifted it back to 2wd and the sound disappeared. I havent been able to get the truck to make the sounds since.

[carkhz316]

You know what, that's exactly what it sounded like. It would make sense as there is a synchro/ blocker assembly in the Tcase that gives you 4WD/ 2WD. I think you figured it out by wiggling the shifter.