07 E350, Recently there has been a howling noise that has been occurring and does vary due to speed but is at its loudest at 40-50 mph. I replaced both front wheel hubs about 2000 miles ago. The rears I think are fine, did the test of driving down a straight and steering left then right, did this and did not hear any change of the sound as the weight transfers side to side. Also it still occurs with the a/c on or off. I did change the rear diff with royal purple 75w-90 but if it is destroying it, I don't think this would make a sound like this and the rear diff would be done by now, did this awhile ago.

So can anyone help out as to where this can be coming from? I was thinking bearings in the driveline possibly, or pulleys

 

Most likely the driveshaft bearing however, don't discount the tires themselves. Those of us here on the forum don't have the benefit of observing and listening first-hand, so our guesses are a stab in the dark as well. Best investment is to take it in to the shop before you start blindly throwing money at it.

 

Did you ever find the cause of the howl? My issue fits your description perfectly. This car is new to me and I'm just starting to dig into the bugs. Cannot manipulate the howl, just always there, most noticeable around 40-50 mph. Does sound like a low howl from a bearing but otherwise all is smooth.
Thanks
2006 E350

 

I have not yet and it has gotten a little more noticeable, so it has to be some sort of bearing. In the next week or so I will buy the center support bearing and the rear wheel bearings and change them out one at a time, will start with the center support bearing first (just b/c this ones easier) then see what happens if no change then the rear wheel bearings as a pair. I will make sure I update you as soon as I do so. By the way how many miles on yours?

 

I have 130K.. Plan was to replace driveshaft bearing this past Friday, but after purchasing I noticed bearing had been previously installed and returned to store. I noticed some fine lateral scratches on the OD. I wasn't about to use a bearing someone else may have damaged. I returned it but they did not have another one until today. Gave me a chance to tool up for this car. My tool box was woefully inadequate. Looks like the entire car is built with torx fasteners. Will report back as well when I complete the swap.

 

I'm at 149K possibly may be the same thing. When you say driveshaft bearing by this you do mean the center support bearing? This thing: https://www.ecstuning.com/b-vaico-pa...114100181~vai/

 

Yes, that's it. I didn't buy the entire bracket/bearing assy, just the bearing. It is possible to replace the bearing alone, for about half the price. We will see if this is the culprit. Otherwise front wheel bearings are next. This was the easiest to change out first.
I am new to MB, and was looking for an inexpensive daily work driver to semi retire my Super Duty. I came across this car and fell in love with its clean looks. I spend 400 miles a week traveling to work and back and wanted a little more comfort than the beloved buckboard I have been riding in the last 15 years. Slowly coming up to speed with all the known issues on this model. I am not naïve to expect a trouble-free relationship. There will be times I'm sure I will hate this car. But when it's right, it sure does ride sweet. And while waiting for my replacement bearing, I did manage to repair that damn broken tweeter in the dash that was bugging the crap out of me..

 

In my experience with rear end noise, it's more of a whine than a howl. It's also always there and gets louder. My Durango needed a new rear and it was embarrassing to drive it with how much noise the rear made. I picked up a junkyard rear for it (only $300) and put it in 40,000 miles ago and it's starting to make noise again. I'm not sure of the mileage of the vehicle it came off of.

 

Well, last night finally had a chance to work on car. Was able to remove the driveshaft bearing support by only removing the rear half driveshaft. ( be sure to add timing marks to halves before uncoupling) You do not need to remove the exhaust, tranny mount, etc. to gain access as some instructions state. A couple of heat shields right below the bearing support, the cross brace under the exhaust, the bolts that secure the bearing support bracket, and the rubber hangers at the back end of the exhaust are all you need to do. If you lower the exhaust at the back end about 4-6 inches, you create enough room to slide the driveshaft rearward and just clear the rear differential. Keep the front end of the driveshaft pointed up towards the floor to give you the angle you need. The support bracket will come right out with it. Anyways, the bearing did not appear to be bad. Still smooth, but who knows. It was replaced anyways. What I did find was a ratchety universal joint, meaning if you moved the yoke from its plane of rotation, it definitely has a flat spot you can feel. In fact the yoke will hold position linearly until you manually move it. It should just flop around. Again, who knows. Not sure how much deflection this shaft normally sees. I know its not right, but if it doesn't flex, then it may have just taken a set in that position. This too will be replaced and I hope this was it. While there, I did notice the output shaft on the transfer case feels a bit sloppy, but before I get stupid..... (sucks chasing down a vibration) lets see if this was it.
Now here is the problem. Looks like MB wants to sell me the entire driveshaft, not just the universal. It is staked in place, no clips used. Local stores do not even list the u joint as a stand alone. I did get the old one out, and will stake a new one in if I can get it.
Searching now for a replacement, hopefully local first. At work now and wish I brought the old one with me to attempt a cross reference.

 

Curious to know whether replacing the driveshaft bearing eliminated the howling noise. On the brink of breaching 130k with my E350 4Matic and the noise is gradually becoming more noticeable. My first guess was a bad front left wheel bearing because it sounds like the noise is coming from that general area, but I know these noises can be tricky to pinpoint so I'm not convinced.