Rear end whine

[C Trost]

’20 XLT HDTow pkg, 40k miles. Rear end developed whinethat starts as soon as move and continues at all speeds. It is a flutter whirl start to slow speeds to a constant whine at high speeds. It is slightly quieter at high speeds. Anyone else have this, or ideas on cause.

 

[99WhiteC5Coupe]

’20 XLT HDTow pkg, 40k miles. Rear end developed whinethat starts as soon as move and continues at all speeds. It is a flutter whirl start to slow speeds to a constant whine at high speeds. It is slightly quieter at high speeds. Anyone else have this, or ideas on cause.

No idea on cause, other than a fluid leak causing low fluid - but repair should be covered under the 5-year / 60,000 miles power train warranty.

 

[Deadman]

How do you know its the rear end? Just curious, not being rude....

 

[ROBERT BONNER]

I have a '20 XLT FX4 Trailer Tow MAX with the 9-3/4" Elsd. And mine whines under forward torque (but not coast/decel) at speeds between 65 and 85 mph. The question about how do I know...I believe it is differential noise because of the direction and frequency, it is high frequency and at freeway speed the driveshaft and pinion are the fastest rotating (highest frequency generating) mechanical pieces on the vehicle. My experience says that the frequency is driveshaft frequency. I think mine has been doing it since it was nearly new. It has 45K miles now. The driveshaft universals are tight and typical in appearance. The ring/pinion has had more slop since new than I would like; however, looking at how the ELSD is designed, the design probably requires more ring/pinion clearance than a standard rear-end. I believe that it is the ELSD "push rods" singing on the fixed ELSD piston. For those unfamiliar with the ELSD design, I've included a link. If I had designed it, I would have used an odd number of push rods spaced at irregular arc angles to avoid resonance.

Eaton IntelliTrac electronic limited slip differential rear wheel drive features

In rear-wheel drive applications, IntelliTrac can neutralize oversteer (when the vehicle is turning more sharply than the intended path) by transferring torque from the outside to inside wheel

videos.eaton.com

 

[VBreithaupt]

I had to take mine in for rear end whine. They had to serve the rear differential . I can you you the more technical work when I get home to and pull paperwork

 

[C Trost]

How do you know its the rear end? Just curious, not being rude....

Put the rear off the ground, put it in gear. Noise clearly coming from the rear differential.

 

[C Trost]

’20 XLT HDTow pkg, 40k miles. Rear end developed whinethat starts as soon as move and continues at all speeds. It is a flutter whirl start to slow speeds to a constant whine at high speeds. It is slightly quieter at high speeds. Anyone else have this, or ideas on cause.

UPDATE: bearings and races in the differential bad. Poor part quality and build installation leading cause. Complete diff overhaul by dealer under warranty. Butter smooth now.

 

[JasonH]

UPDATE: bearings and races in the differential bad. Poor part quality and build installation leading cause. Complete diff overhaul by dealer under warranty. Butter smooth now.

Ford quality strikes again.