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1 What would cause a knocking noise when downshifting a manual?
I hit a pothole a few weeks ago which may or may not have had something to do with my problem. At first I had knocking/banging when backing up (especially up a hill). The shop rebuilt my transmission, replacing worn out bearings and clutch and resurfacing the flywheel. Well now I still hear the noise, not as loud, when downshifting. I also heard it once when starting the engine.
My father in law found a metal strap with grease on it in his driveway and I am pretty sure it goes to my car, but the shop says no.
Also, the said the engine mounts were fine.
This is a 2008 Mazda 3 2.3L manual with 120k+miles.
Update
They said they checked everything external first and narrowed it down to the tranny. Right now it is just when downshifting and starting the engine. before it was engine starting and backing up. I do have a shake 55-60, but have had that for awhile. I was told that was my struts.
I think maybe I need to take it to a Mazda dealership for them to examine.
Cette question est-elle utile ?
2,3k 
Did you get them to look at your drive shafts while they rebuild your transmission and all the mounts? Checked your front end for any worn or bend pieces? Just trying to narrow it down a bit. Is the noise heavier when you rapidly step on the accelerator? Any shakes, rattles when you drive.
par oldturkey03