Driveline grinding/chafing noise while at highway speeds and not under load

[Snowboarder12345]

So yesterday was the first time since I've begun modifying my pathfinder that I have taken it out onto the highway. Over speeds of ~60kmph I get a grinding noise when decelerating, either by just backing off the accelerator or by depressing the clutch pedal. When just backing off the gas the noise happens for a few seconds and the goes away again, but when I press the clutch pedal the noise is louder and does not go away. In both cases the noise is worse when going downhill as opposed to just being on the flats.

 

I think my clutch throwout bearing is on it's way out, so I'm wondering if this could also cause my high speed noises. However all the reading I've done leads me to believe that this isn't the case. The U joints on the driveshaft are brand new, so they shouldn't be the issue. The one other thing that comes to my mind though is that my differential and transmission angles may be out of alignment enough to be causing this, but I'm not sure what symptoms would be present if that were the case. Anyone have any ideas as to what could be causing this?

[Snowboarder12345]

Oh yeah, I got a short video of the sound.

 

[Citron]

I think if it was the driveshaft you would experience the symptoms all the time, and it would be worse when the angle increases, like going over bumps or flexing. You should be able to find a spec for max drive line angle and measure yours to see if it is in spec.

 

To me, the fact it does it continually while the clutch is in, makes me think throw out bearing. However, it is odd for the throw out to do it when the clutch is out and you are decelerating, in my experience.

[Citron]

What does it do when engine braking?

[Snowboarder12345]

Same noise, just not as loud and it goes away after a second or two.

[Snowboarder12345]

So as it turns out, the gears in my differential were shredding themselves. Wear pattern indicates that the pinion was too close to the ring gear. I am not sure if this was somehow caused by something I did when I installed my airlocker, or if it may have been caused by stresses from the lift on old parts. I haven't pulled the carrier apart yet and had a look to see how the pinion bearings look, but my suspicion is that it may have something to do with one of them being worn or failing. While there is almost no noticeable play there is a slight chafing sound when the pinion is rotated by hand. But I really have no clue as of now. The new gear set is on the way though, so when that gets in and I start pulling things apart more maybe there will be more answers.