I'm having exactly the same sound and problem - it just cropped up this weekend on a long drive. Sounds like an owl is trapped behind the dash or in a wheel well, and I can feel the slight vibration in the accelerator pedal. It happens when I hit 45mph, and was intermittent at first and now happens every time I hit 45.

I have it at the shop down the street to see if they can diagnose it. My money is on a wheel bearing. It sounds like from this forum the same sound could happen with the speedometer cable, but my speedo isn't acting weird.

I'll post what they come back with.

Well my mechanic thinks the problem is the driveshaft bearing. The bearing support is obviously total rubbish and the bearing is making noise as well. It's hard to tell if it's the same noise but we'll replace it and report back.

He took the wheel bearings out and said they seemed fine...

Good luck Treeman.

Took the car to a trusted Mechanic, We went on a test drive, we had maybe got out of his driveway. and he say's RearEnd, after another 10th of a mile he say's strong chance it will be passenger side rear wheel bearing, but still could be the Diff. We will soon find out as I am taking it to one more guy to get his diagnosis. Thought I would share what I found so far. Will let yall know what the second opinion is. I want to Thank everyone for input. I appreciate you guy's and the entire forum Happy New Year!!!

__________________
Collector of Fine Hose Clamps
'77 240D 'AVA' is in heaven now
'80 240D Kanarienvogel
'82 300TD 343k was my daily driver 'ADOLPH' In Surgery for a severe Deer Bite to the Nose
'88 560SL 102k 'White One'

Does the tone change in pitch with a change in speed? If so then it could be a wheel bearing or a bearing in the diff.

If it does not change in tone, check your brake lines for flexibility, bleed your brakes (flush them, not just a single bleed) and then test the car.

I had a howl in the rear of my 1978 300D that didn't change pitch and it turned out to be a stuck caliper. Bleeding the brakes got me by for months but the caliper was just diagnosed as really stuck by my friend, who bought the car from me.

If you hear only one single tone then it's most likely the brake pad heating up the piston, heating up a small amount of water which expands and vibrates the pad against the rotor at a constant frequency.

If the tone changes, then look at the wheel bearings and the differential. You can save a lot of money if you do the work yourself. A LOT.

Before you get into all the expensive stuff, try fixing the easy stuff first.

Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

I took it to a Transmission shop. The Owner told me it is nor a wheel bearing, throwout bearing, locked brakes. He agrees with RollGuy it is the Center Support or Drive Shaft Support Bearing. I pulling the one off my parts car ant try to slap it in.

Here is a video I made to get the noise for yall. I know I sound like a Hillbilly, I am a Hillbilly. Thanks for all the help. The 1980 240D Howler - YouTube

__________________
Collector of Fine Hose Clamps
'77 240D 'AVA' is in heaven now
'80 240D Kanarienvogel
'82 300TD 343k was my daily driver 'ADOLPH' In Surgery for a severe Deer Bite to the Nose
'88 560SL 102k 'White One'

I know a hillbilly when I hear one, and I also know a center support bearing noise when I hear one. My vote is yes on both

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All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html