Unusual Noise at 40-50 mph

[sharpsicle]

All I could think of when you talked about getting it to speed on jack stands was this....

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[869 KPH]

In my garage, I put the rear on jackstands, shut off ESC, and slowly ran it up to the speed that it typically makes the most noise - 46-47mph. With the windows down, I could hear the rear end, but it didn't sound 'bad', and the noise didn't get noticeably louder at 46-47mph like I have noticed previosly with the windows closed.

Cam, that you?

 

[869 KPH]

All I could think of when you talked about getting it to speed on jack stands was this....

Yes, @sharpsicle, I could not find that gif!

 

[Maximus Gladius]

Another Update:

In my garage, I put the rear on jackstands, shut off ESC, and slowly ran it up to the speed that it typically makes the most noise - 46-47mph. With the windows down, I could hear the rear end, but it didn't sound 'bad', and the noise didn't get noticeably louder at 46-47mph like I have noticed previosly with the windows closed. So, I figured the noise must be coming from the front end. However, with the windows closed, I could definitely hear the noise and it 'spiked' at 46-47mph. So, the noise is related to the transmission/driveshaft/rear end.

I had my son ramp up speed while I used my mechanics stethoscope on the rear end, driveshaft center bearing, and transmission output. It seems to be the input pinion bearing making the noise, but it is fairly consistent. So, outside the vehicle 'by ear' or with the stethosope the rear end noise sounds fairly normal, although slightly higher frequency than I would expect, and it varies drectly with speed - no spikes in volume. Driving down the road with the windows open, I can't hear anything abnormal sounding at all - even when next to a jersey barrier or going under an overpass at the critical 46-47mph speed.

So, I can only notice the noise with all the windows shut and the radio off, and it seems to have a resonance at 46-47mph and again at 58mph.

Next step is to look at the parking brake cables, since they are attached to the rear diff via a metal bracket almost directly above the pinion bearing area.

What is the MILAGE on your vehicle?

 

[jac04]

All I could think of when you talked about getting it to speed on jack stands was this....

Yeah, me too.

 

[jac04]

What is the MILAGE on your vehicle?

2200 miles.

 

[Maximus Gladius]

Tried rotating tires or maybe have a set of winter rims/tires you can swap out and try?

 

[jac04]

Tried rotating tires or maybe have a set of winter rims/tires you can swap out and try?

It's not the tires. It makes the noise with the rear end on jack stands.

 

[jac04]

UPDATE:

I disconnected the stamped metal bracket that connects the parking brake cables to the rear diff housing. I stuffed a piece of medium density foam between the bracket and the diff housing and the noise in general can't be heard any more, and the resonance 'spikes' in noise volume went away.

So, I removed the metal bracket from the cables and made a spacer to hold them separated from each other.

 

[869 KPH]

UPDATE:

I disconnected the stamped metal bracket that connects the parking brake cables to the rear diff housing. I stuffed a piece of medium density foam between the bracket and the diff housing and noise in general can't be heard any more, and the resonance 'spikes' in noise volume went away.

So, I removed the metal bracket from the cables and made a spacer to hold them separated from each other.

Way. to. go. lol would be interesting to see if this bracket is revised in a future MY, all thanks to you. If I worked for Stellantis I would know these kinds of threads forwards and backwards.

 

[jac04]

Way. to. go. lol would be interesting to see if this bracket is revised in a future MY, all thanks to you. If I worked for Stellantis I would know these kinds of threads forwards and backwards.

Hahaha, thanks! I think I'm the only one bothered by the noise, or who even noticed it, so I doubt my experience will result in any changes.

 

[Hipbilly]

I just had a re-gear performed and am 99% sure I'm hearing my rear ring & pinion groaning at that speed, sounding like that... Mine stops when I let off the throttle and unload the torque, though.
I'm gonna have the gear guy drive it and see what he thinks,
This bracket isolation may be in my future if he doesn't believe it to be an issue...

 

[jac04]

I just had a re-gear performed and am 99% sure I'm hearing my rear ring & pinion groaning at that speed, sounding like that... Mine stops when I let off the throttle and unload the torque, though.
I'm gonna have the gear guy drive it and see what he thinks,
This bracket isolation may be in my future if he doesn't believe it to be an issue...

If the noise changes when on/off throttle, then it is a problem with either the gear set-up or the bearing preload (IMO). But, getting someone to admit it can be a problem, especially with aftermarket gearing. My 2014 JK Rubicon had rear pinion bearing noise that changed when on/off throttle and Jeep couldn't have cared less and told me it was normal. ECGS ended up building me a HD replacement rear axle assembly that has been quiet for the last 25k miles.

 

[dcmdon]

I know I said I was going to forget about this, but against my better judgement, I've kept looking into this... It is more of a challenge to me now to try to figure it out.

I aired down my front tires to 28psi and the noise is still there - it sounds exactly the same and happens at exactly the same speeds. So, I think this rules out the tires (at least the front tires, and the noise sounds like it is coming from the front).

I also put the trans in N and shut off the engine, and the noise is exactly the same.

Changing between 2WD, 4H Auto and 4H has no impact on it. I have Selec-Trac.

Turning side to side doesn't appear to change the noise, although it is difficult to tell because of tire noise when turning side to side at 46 mph.

I dropped the glove box and used a piece of 3/4" rubber hose to listen the the area behind the dash, and the noise does not appear to be originating from inside the vehicle. However, when I put the windows down I can't hear any external noise over the wind noise.

So, I'm down to possible causes (things that are always the same based on road speed):
Front wheel bearing(s).
LH side front diff carrier bearing.
Something transmission or Selec-Trac related.
Rear drive shaft, wheel bearings, diff bearings (although noise sounds like it is coming from the front).
Some electrical component that would be active without the engine running and would change based on road speed (???)

I'll keep you posted if I ever find the source.

You would do well in any field that requires attention to detail.

Have you thought about becoming a quality engineer?

Ha.

 

[Hipbilly]

...getting someone to admit it can be a problem, especially with aftermarket gearing.

I am slightly nervous about that, but its a new, small, family owned gear & axle shop, and they seemed very knowledgeable and have a warranty. I'm hoping they stand behind their work.
I was surprised when he told me I DIDN'T need to come in @ 500 miles for a fluid change and inspection, though...

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