Hi,

I have been noticing this along with harder shifting in the past month.

I read about the vacuum modulator/lack of vacuum/etc. However, it seems that it only affects downshifting when coasting to stop.

My problem is especially noticeable when I floor the car at low speeds (20-30mph). I would hear a clunk from the rear (in front of the rear diff I think)

At high speed downshiftings, it's not there.

I then decided to drive around the parking lot and apprently when I put it in D and hit the gas rather hard I could hear a slight clunk too.

The sound is also there when I hit the gas when the tranny is in P or N (could it be the exhaust system?)

or is it the Rear Flex Disc? I had a glimpse of it and it seemed allright.

and yes, I am very positive that it's from the back of the car.

Thanks!
-Holson-

I think I'm gonna get the car checked tomorrow.. will let you all know.

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2008 BMW 335i Coupe

may be u want to follow

http://www.peachparts.com/shopforum/showthread.php?threadid=40484

mvk

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One penny saved is three penny earned.

1985 300D Turbo 179,000miles

Check the flex disks, differential mount, and vacuum system. An excessively hard 2-1 downshift will make the rear end thump.

Also check the differential bushings -- they can be bad, as can the rear carrier bushings. Anything loose will cause a thump.

You could also have a loose exhaust that thumps when you floor it, too -- check the rubber hangers and the condition. Not a typical problem.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

You have the best of all possible situations... So be happy ! It is the noises that will only happen when traveling which are difficult to find.. Many uppity MB mechanics refuse to ride in the trunk or under the hood at even reasonable speeds.... even in parking lots....to find moving specific noises.... those snobs....

If it will make the noise when in PARK then you get someone to hit the throttle while you prob underneath the car... Be SURE they understand the concept of LEAVING THE CAR IN PARK......you might even apply the parking brake ....

Take a long metal tube with you and place one end to the little flap on your ear... and push the flap in to close the usual ear opening... do not stick the metal rod into your ear....

Then you can put it various places on the frame drivetrain or exhaust and have a good chance of finding your noise producer.

If it will do it in park it pretty much eliminates all the moving objects behind the transmission. It does not eliminate things in the trans... but that is not a likely suspect from what you have described... ( Why is there not an icon for "good luck" ? perhaps a four leaf clover ? ) Greg

Well took it to a different shop than the one I usually take it to....
http://www.peachparts.com/shopforum/showthread.php?threadid=40536

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2008 BMW 335i Coupe