Humming Noise at high speeds

[Jamusky11]

2020 Ram 1500 - 60k miles. Recently on a long trip I started to notice a humming noise coming from what seems like the rear of my truck. It only happens at speeds above 80MpH. It happens with or without cruise control. It only happens when accelerating as once you let off the gas it immediately stops. It is intermittent and only happens when accelerating. No other symptoms. Anyone know what this may be?

 

[stevj]

Does pitch change with speed?

Steve

 

[Jamusky11]

No. Pitch comes and goes with acceleration either during cruise control or pressing the gas. But the pitch wound remains the same the entire time.

 

[stevj]

Well, that would rule out most drivetrain/carrier bearing/drive shaft/differential issues.
My suggestion, then, would be to go over the Ram's exterior and underneath to look for a loose body panel, trim piece or anything that may have enough give or play that it starts fluttering or vibrating due to wind turbulence caused by vehicle speed.
Is your Ram the new body style (DT) or classic body style (DS)?

Steve

 

[Jamusky11]

Mine is the new body style. It seems odd that it would be a loose body piece when I can make the Boise stop immediately by letting off the gas. I will take a look just in case though.

 

[stevj]

It seems odd that it would be a loose body piece when I can make the Boise stop immediately by letting off the gas.

Tossing out ideas, no matter how illogical. Don't dismiss any possibilities until you've verified and can definitely rule it out.
Do your tires have an aggressive tread pattern?
Also check motor and transmission (and transfer case if you have 4x4) mounts. Could be under acceleration or at high speed, one side is unloaded enough through driveline twist to cause a vibration.

Steve

 

[HemiDude]

Hum or whir on light acceleration in a specific speed range sounds like the rear end to me. I would start by changing the rear diff fluid, check for any glitter or debris in the fluid and refill with correct viscosity (and modifier if LSD). If you see anything in the fluid, drive it for a short while and change again.

 

[stevj]

Hum or whir on light acceleration in a specific speed range sounds like the rear end to me. I would start by changing the rear diff fluid, check for any glitter or debris in the fluid and refill with correct viscosity (and modifier if LSD). If you see anything in the fluid, drive it for a short while and change again.

Yep.
I was wanting to point to a driveline component originally, but after he indicated the hum pitch didn't change with speed, I was just "shooting in the dark" as they say.

Steve

 

[RiffWrath]

My guess is axle bearings. Had a instructor who owns a garage tell our class 2019s were bad for rear end bearings and scored axles were quite common repairs in his shop.