Driveline noise mystery... need some help diagnosing

Hoping you guys will be able to help me narrow down the source of some driveline noise.

The Noise
It's a howl that occurs mostly at 53-62 mph but only under light throttle to maintain speed. Applying or letting off the gas makes it go away. The noise starts to be come slightly noticeable at just under 50 mph. There also seems to be a lower frequency sound at about 35 mph -- a very light (barely noticeable) roar, if you will.

History
I had 4.88's installed in the spring by a local shop. The noise started to appear during the break-in period, so we naturally assumed it was the gear setup. The shop made two additional attempts with new gears and bearings each time. By all accounts, the setup (pattern, preload, etc.) was perfect, but the noise remained. I continued to believe (perhaps incorrectly) that the setup was not right, so I bit the bullet and had an ECGS third member installed last week. Yes, the noise continued -- you've got to be kidding!!

Other Info
The truck is a 2016 5.7 4WD and has 55K miles. I have towed a 6500 lb boat/trailer since new (about 2500 miles/year). I've also had to submerge the rear wheels past the hubs at the boat ramp several times. Since January, I've installed Bilstein 6112/5100's, Toytec shackles, diff drop kit, carrier bearing drop kit, and 34" tires (this is NOT tire noise, given that I can regulate it with throttle).

So now I can only conclude that the noise is coming from elsewhere in the driveline other than the diff -- I mean what are the chances that four gear setups (from two different places) would produce the EXACT same noise under the EXACT same conditions? Perhaps the noise starting during the first 4.88 break-in period is just a coincidence. Possibilities in my mind:

• Center Support Bearing
• Wheel bearing (seems unlikely since I can regulate with throttle)
• Transfer case

What do you guys think? Yes, I ultimately need to get it diagnosed at a specialist, but thought I'd challenge the forum with this mystery.

 

The throttle body gasket has a wire screen that causes a high-pitched whistle under certain loads and throttle positions. Is there any chance that’s what you’re hearing?

 

I'll definitely look at that, couldn't hurt, but the noise sounds more mechanical than a whistle.

 

The guy that did mine said, that Nitro Gears are made in India (if I remember correctly) and they are not using one type of metal in the forging process (recycled steel)and it's actually caused by the harmonics of the gears making contact with each other. Mine happens at 55 to 58 mph.
When I did the service on the differentials there was zero metal and zero wear.

 

It’s easy to do the driveshaft and carrier bearings. Then you don’t have to worry.

Or take it to the shop and ask. That could do it.

 

I've been told the same... that it's just the nature of these particular gears. Seems strange that we don't hear about it more given the number of people who have installed 4.88's.

Yes, it's gonna come to that.

 

As long as theres no metal pieces or wear, I'm not too concerned.

 

If that's what I'm hearing and it's just nature of the gears without doing harm, then I guess there's not much I can do.

Hoping it's something else.

 

I have a 2019 and around 2500 miles I'm experiencing the same exact issue. My old Taco had the same noise and it was the wheel bearings. I can't believe wheel bearings would be going out so soon, but anything is possible. My guess is that it is the carrier bearing(s). My dealer also told me it was the throttle body, but then the noise should be at that same RPM no matter the speed. I manually shifted down to hold the RPM at a lower speed and it did not make that noise. Only at 50-55 mph. It's getting louder and I can hear it over my radio. I'm planning to go back to the dealer and talk to a different tech. I'll keep everyone posted.

 

Very interesting, please keep us posted. I just changed the diff fluid in the ECGS unit and it was clean as I've ever seen it, so I'm really not worried about the diff. Hoping it's the carrier/support or wheel bearing.

 

I can definitely relate to this.

To keep a long story short, I had Nitro (REM Polished) 4.88s installed on my 2018 a few weeks ago. Needless to say, i experienced the exact same howling/whining within the parameters you described. So, the shop set up the gears for the 2nd time, with a very slight shim adjustment. On the way home, around 55, the whine/howl was much more pronounced.

Lastly, the shop want's to "Make it right", so I tell the shop owner that this will be their final attempt at solving the issue. At this point, the owner is blaming the Nitro gears, and asks me if I'd mind if we go with Yukon, I said "ok".

So now the Yukon 4.88 is installed, and I'm still experiencing a very slight whine. I have about 200 miles left for the break in period, then I'll hope there's no excessive metal in the fluid. So far, the noise is far less than before, and at times, I can't hear anything at all.


I do have an appointment with an axle/gear shop next week. I'll post what they tell me.

 

Well, just heard from the Dealer. The noise is normal. They are telling me it's the air coming in thru the intake (butterfly) that's making the noise. They drove other 2019's and experienced the same noise. At this point, I'm thinking of installing an aftermarket cold air intake, or something to get rid of the noise.

 

Aftermarket intakes make it louder in most cases. And it’s that screen in the throttle body gasket I mentioned, P/N 22271-50050 for a 5.7L Sequoia seals the same, just no screen, no whistle.

Or you can cut the screen out of your existing gasket if spending < $10 on the gasket is too much. LOL.

 

Glad to hear it's resolved for you. I'm just surprised that noise from the throttle body would be so similar to a whine or howl from the drivetrain.

 

Thanks everyone for the help! I will plan to order the gasket/seal.

 

I have Nitro Gears 4.88s and am experiencing the same issue. Good to hear others have the same circumstances.

 

Yukon gears do have some noise also, Put them in a '67 Camaro 12 bolt. Best driveline people in Orlando. No matter how may times re-done still some noise. Changed gear lube to Redline high shock. Helped some. Check out web for Yukon gear noise- reports everywhere of the same. 34ford