Excessive/high-pitched whining with 4H Auto on (5.13 gears)

[ryanlsmith]

I got my truck re-geared some time ago, and initially I felt there was a concerning whining (in 2H) that starts around 60-65mph. I had the shop double check, although I don’t think they really inspected anything. It either finally settled in or I got used to it, as it’s not something I notice much anymore.

However, with the recent rain I finally put it in 4H Auto and there is a noticeable high pitched whine after 60-65 that gets nearly unbearable. Interestingly it only seems to happen under load.

What I’m really confused about is why 4H Auto would cause this. From my understanding, the front diff isn’t actually under power most of the time, so I assume it’s not coming from that. Is there something about this mode that induces more load on the rear diff? Or is it the axles (although the whining is surely coming from the gears)?

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[dcmdon]

I can't really comment intelligently on the load paths that the gears in the front diff experience when "coasting" in 4H auto.

But I can tell you that the Front Axle Disconnect (FAD) connects in 4H Auto. So something IS different in 4H auto.

But then again, the fact that you get more whine under load is confusing.

 

[dcmdon]

To those who really understand the inner functions of AlfaOBD or JScan, is there a parameter you can monitor that will tell if the front is being brought into play in 4H auto?

I assume its a clutch pack that brings the FWD into play.

 

[ryanlsmith]

But then again, the fact that you get more whine under load is confusing.

Yea, it lingers for a second after letting off the gas, but the second I touch the throttle even lightly it immediately comes back.

 

[ShadowsPapa]

To those who really understand the inner functions of AlfaOBD or JScan, is there a parameter you can monitor that will tell if the front is being brought into play in 4H auto?

I assume its a clutch pack that brings the FWD into play.

Yes, you can monitor the whole thing with JSCAN.
Over about 30% throttle the clutch pack begins to engage, let off and it relaxes.

Go to sensors, drive train control, choose actual transfer case lock torque, t-case status (shows what mode you have selected with the lever), you can choose throttle position to show how much throttle it's being given, etc.
IMO, works best or is easiest to view in "boxes" mode for the display.

 

[ryanlsmith]

Yes, you can monitor the whole thing with JSCAN.
Over about 30% throttle the clutch pack begins to engage, let off and it relaxes.

Go to sensors, drive train control, choose actual transfer case lock torque, t-case status (shows what mode you have selected with the lever), you can choose throttle position to show how much throttle it's being given, etc.
IMO, works best or is easiest to view in "boxes" mode for the display.

Sounds like that explains the behavior then. Taking it to a new shop next Tuesday to have them inspect. One thing that worries/frustrates me is the original shop said not to worry about break-in for the front since "most" of the load is on the rear. While that may be true, I hope there wasn't pre-mature damage done by throwing highway speeds at it without a proper break-in. It's been a long time since the install, but I think I had 4H Auto on for some of the initial low-speed break-in, but definitely not part of the overall procedure.

 

[dcmdon]

Sounds like that explains the behavior then. Taking it to a new shop next Tuesday to have them inspect. One thing that worries/frustrates me is the original shop said not to worry about break-in for the front since "most" of the load is on the rear. While that may be true, I hope there wasn't pre-mature damage done by throwing highway speeds at it without a proper break-in. It's been a long time since the install, but I think I had 4H Auto on for some of the initial low-speed break-in, but definitely not part of the overall procedure.

I think you are over-thinking the break in importance.

Sure it's beneficial overall. But it's not going to self destruct if you break it in incorrectly in all but the most extreme situations.

In this case, we're not talking about a lot of torque being put through the differential since its at most 50% of what's being used to move the truck, and most if the time is far less than that.

 

[Escape.idiocracy]

No better way to tell than to open the pumpkin and take some photos of wear pattern….(post them back here!)
Pick up a dial indicator and check the backlash….. this is easy stuff don’t be intimidated…
Checking the pattern and the backlash will let you know if your gears are wearing right.
The only other thing that’s more difficult to check is if they put preload on the carrier bearings….. I suppose the easiest way to check that would be remove the caps and see if you can slide the carrier out by hand… if not then the write up is too detailed…. Lol you would need a case spreader.
Start with the west pattern and backlash!


bad carrier bearings in my experience sounds like a howl that will progressively get worse…. The crappy part- if you are running MT tires- it’s a similar sound when you increase speed the tire noise gets louder… so do the bearings.

 

[ryanlsmith]

No better way to tell than to open the pumpkin and take some photos of wear pattern….(post them back here!)
Pick up a dial indicator and check the backlash….. this is easy stuff don’t be intimidated…
Checking the pattern and the backlash will let you know if your gears are wearing right.
The only other thing that’s more difficult to check is if they put preload on the carrier bearings….. I suppose the easiest way to check that would be remove the caps and see if you can slide the carrier out by hand… if not then the write up is too detailed…. Lol you would need a case spreader.
Start with the west pattern and backlash!


bad carrier bearings in my experience sounds like a howl that will progressively get worse…. The crappy part- if you are running MT tires- it’s a similar sound when you increase speed the tire noise gets louder… so do the bearings.

Normally I’d attempt, but running out of time. Taking it up to Portland/Seattle (10hr drive) for Thanksgiving week and just want a quick inspection from an expert. Between wrapping up some wiring and getting my steering components dialed in, I need to check off a lot in a couple weeks.

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