Tracking my noise, from AWD gauge to possible turbo failure

[Junkyard_Mad-Scientist]

2 things off the bat, 1. Yes I know my PTU is probably singing its swan song. 2. I know it's a gimmick gauge.
Now that's out of the way, my car hasn't had typical noises/ behaviors of what I've seen for ptu failure but its definitely something in the driveline around the middle of the car, noise is hard to pinpoint. I was watching my awd gauge and noticed the rear never fully goes away like the front does, only at a dead stop. So my thinking is possible rdu issue? I don't know, maybe it's normal gauge behavior. Here's a few screen shots of a video of mine for comparison, anyone with the gauge enabled can you take a look and see if yours behaves the same as mine?

Cruising

Coasting

Full throttle

 

[Majestic]

I think the PTU spins at all times.

 

[kryptto]

Pretty sure the PTU runs all the time, sure could be the rdu. Change the oil yet, if so what's it look and smell like?

 

[Texas Marauder]

Normal. The PTU and driveshaft are always turning. The RDU is what enables rear axle engagement. The RDU is always minimally engaged. FORScan shows the lowest engagement percentage at 3.53% on my car. That's in park or neutral or drive. I don't know if others are different. The RDU engages much more than you may realize. It's a varying percentage.

As far as a noise around the middle of the car, check the carrier bearing on the driveshaft.

 

[Junkyard_Mad-Scientist]

I know the ptu is always spinning, its essentially a big differential, but the level of engagement for the rdu is what I was curious about.

I would imagine it would be same or less than the primary front drive wheels which is why I was confused by the gauge showing more activation than the front at coast. It also goes away completely at a stop so it's varying level of engagement if the gauge is accurate at all would mean it's engaged more than the front at coast creating drag.

I was wondering if possibly the clutch in the rdu could be causing some issues or be the issue itself. Almost like a bind in the PTU since it's receiving in theory, drag from the driveshaft. My noise goes away when I get into the throttle and see the rear axle activate (past the level that doesnt go away) on the gauge. I plan to do a more in depth test with forscan but I figured I'd throw my theory out there.

 

[kryptto]

Still did you change the rdu?

 

[Texas Marauder]

I know the ptu is always spinning, its essentially a big differential, but the level of engagement for the rdu is what I was curious about.

The PID for the RDU is in the PCM. Yes, AWD Clutch is the RDU.

 

[Junkyard_Mad-Scientist]

Still did you change the rdu?

Not the fluid no, I was so concerned with the PTU I did the fluid a little early and didn't worry about the rdu. I suppose I can tack that on to the to-do list for this weekend and get an analysis on the fluid.

 

[Junkyard_Mad-Scientist]

The PID for the RDU is in the PCM. Yes, AWD Clutch is the RDU.

View attachment 94563

This will give me a baseline and know what PID to look for, thank you.

 

[Junkyard_Mad-Scientist]

Okay just took it for a long drive with the wife watching all kinds of systems. First was the awd PID, seems to be operating normally, only getting up to 6.xx % when coasting compared to a normal and at a stop 3.53.

The noise does not increase with speed but can be replicated at multiple speeds, only in certain rpm ranges though. So we watched the turbo bypass on/off and compared the noise to that and the rpm range. It starts around 1000rpms and gets its loudest (still faint, all hvac and radio off) around 1400 rpm, between 1400-1600 rpm it gallops inconsistently, beyond that the noise goes away. But as soon as I let off the throttle and the bypasses open it goes quiet.

I tried to replicate it in gear at a stop with my foot on the brake to put it under load with no luck, but then, the noise went away completely while driving. I'm kind of stumped and will be physically checking things this weekend but is it possible it's the rear turbo? I installed a cheapo cone filter I got for free and now I can hear more intake noise and a slight whistle or more like metal screech when it's making the noise.

The car isn't down on power, there's minimal smoke if it's not evaporation out the tailpipes and it's even. Front turbo is good I just checked the shaft a month or two ago, and it drives perfectly.