Cole Hudson

Hello All,
​​​​​
​​​​​​I have an issue with my 2013 E350 Cabriolet where there is a humming/roaring sound coming from the rear end. I thought it sounded like tire noise so I replaced all 4 but the noise persists. It starts at about 20mph and goes through about 80mph and increases in pitch the faster I drive. I'm thinking it could be diferential or bearing related but I'm not entirely sure. The car only has 14,000 miles on it (sat in a garage most of its life until I got it). Since I've owned it, the sound hasn't gotten worse, but it never goes away. I have one Service record but it doesn't say anything about the diferential oil being changed. Any help is greatly appreciated. Cheers!

Plutoe

Put on a lift check the fluid and then run in gear while seeking to localize the noise bla bla bla

Chevota

Interesting.... I'd check the ring/pinion for play, which happens if they decide to start wearing. Imo once they go they go fast and the play goes from barely anything to a lot. Hard to tell for a noob tho, but the dealer guys will know. Another check is the oil, if they wear the diff oil will have mass metal in it which gives it a metallic paint look. You can also put a strong magnet in the oil and if gear metal is in there it'll collect on the magnet and look like ferrofluid (google pix of it)
Other than that, from what you described, it seems like its the differential one way or another so I'd either start tinkering, or take it to a shop.