Chrome988

I just bought a 2009 e350 4matic. 170k km.
There is a loud howling sound audible at speeds greater than 70km/h. Gets louder with speed. Seems to come from rear of vehicle.

Have taken to 2 seperate mechanics, who have test driven vehicle and put it up on a hoist
Both independently conclude that the noise is coming from the rear diff.

No play in wheel bearings. No noise with stethoscope.
No asymmetrical tire wear, and at least 50% tread.
Moving rear tires to the front did not change any characteristic of the noise, it's still coming from the back.
Rear diff fluid changed recently with proper mercedes spec fluid, no difference in noise, still present.
​​​
​Besides the annoying sound, car drives smooth and great with full power, no lights on the dash.

Question:
I am annoyed by the noise and want to get it fixed.
I am looking at getting the differential rebuilt.
Does anyone know any shops in the GTA that will rebuild differentials? I have no idea who to go to, I live in Barrie.

Plutoe

you may also want to replace with a used diff or get a new ring and pinion set------google diff repair
what amazes me is that you did not notice the noise in your test drive

Chrome988

It was raining during test drive and the previous owner told me the tires were loud, and they are 6 year old Chinese tires, so I got deceived into thinking it was tires.

Onyxthecat

It's the pinion bearing. Mine was also doing the same thing as yours and my diff fluid was silver from the bearing getting chewed up. I had my local euro shop rebuild mine using a kit from ebay using NTN bearings and its smooth and quiet now.
https://www.ebay.com/itm/31397599803...3ABFBM2JO6j4Rk

Chrome988

Thank you for sharing your experience.
I took the car to a transmission shop and they confirmed the same thing. I have purchased a bearing kit from ebay, similar to the link you provided. It arrived on Friday, so I am planning on dropping off the car to the shop again tomorrow, and I hope for a good result like yours. The ebay seller I used is named benzexpert, he had good reviews.

Onyxthecat

Very good. Update us when it's fixed! Good luck!