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F-150 Rear Diff Noise

I have a 2015 Ford F-150 4x4 2.7 Ecoboost that I use to haul a trailer for my business. I have installed an airbag system and use a weight distribution hitch due to the trailer tongue weight being rather heavy, but still within the 1200lbs limit. My truck makes an awful rhythmic grinding/clunking noise that increases with speed and it only makes this noise when I am towing. The truck does not make any noise when the trailer is not hooked up. The U joints are fine and there is no clunking or slipping with the transmission. I have taken the truck to the mechanic, but he could not find anything wrong with the truck. I am thinking it might be a pinion bearing or something in the differential, but I have not been able to find anyone that has had the same problem. Any ideas?

Pinion bearing sounds possible. Transfer case bearings could be possible also. A good drivetrain shop should be able to check for play in the t-case output shaft and the yoke on the rear differential.

The “integrated wheel ends” (IWE’s) on those model 4wd trucks sometimes give problems. It is what automatically locks the hubs when 4wd is engaged. They’re controlled by vacuum, and when they lose vacuum, they tend to try to half way lock when in 2wd. But this would be a grinding sound in the front, and towing shouldn’t make a difference.

Don’t forget to check the trailer. Noises may transmit through the tow bar.

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Wait a minute.

Is the towing capacity 12,000 lbs., or is the tongue weight capacity 12,000 lbs.? You need to differentiate and make sure you’re not exceeding either one. If the trailer is under towing capacity, but the tongue weight is over the tongue weight maximum, adding a heavy weight distribution hitch isn’t going to help; you still have to stay under tongue weight capacity.