?? Ever hear this clunking noise ??

[m3f_speagle_641be587f7]

Ok guys...have had a few little problems with my M during this first month i owned it. Most of them are common with most owners though, such as power steering and C.C. malfunction, and problems with the clutch not returning ..but i have a new one today...



When driving, up shifting is fine..no problems..but i began to downshift and once i hit second gear, i heard a clunk or a thump right as i released the clutch. Then i downshifted into first and i got the same noise. The noise sounds like its coming from the rear end of the car..but i can't be too certain. Possibly from down below towards the rear..i really dont know though.



Anyway..so I haven't noticed this clunk any other time except downshifting into first and downshifting into second. When i double clutch or if i just match the rpms during the downshift, i dont hear the sound at all.



Any suggestions..i just am praying its not gonna be a serious tranny problem

[m3f_CMT_50ca834bd5]

It could be the old notorious differential bolt - get the car up on a lift, or find someway to check if the main bolt affixing the differential to the car is loose. This same thing has happened to me twice.

[m3f_speagle_641be587f7]

Ok..so are you saying its something i maybe can just tighten. It is external, right? so i'll be able to just see it?

[m3f_speagle_641be587f7]

ok..i have it jacked up...is it a bolt attaching the differential to the cross member..or is it a bolt attaching the diff. to the body?

[m3f_Sirius_880bd69485]

Its located around the bottom of the diff. You can't miss it.

[m3f_PiZark_bed94aaf5c]

i just had that problem fixed it was a broken diff bolt

[m3f_speagle_641be587f7]

Everything seems to be there and tight..doesnt look like anything wrong...i found the hex bolt in the front that attaches the diff. to the cross member...nothing wrong with it....



any other possibilities?

[m3f_PurpleM3Pursuit]

yeah usually if it sounds like a bowling ball is hitting the rear seats in ur car, its the diff bolt.. kinda sux..



but i don't know.. did u check the tranny mounts?

[m3f_Sirius_880bd69485]

A bad tranny mount will cause more of a funky vibration right under your seat, instead of a clunking, as will broken engine brackets.



However, a bad tranny mount/bracket can also cause quick thumping noises under moderate/hard accleration.

[m3f_speagle_641be587f7]

hey thanks for all the advice once again...i ended up jacking up my car and lookin at all the bolts to the differential. 4 of them connect it to the body and one to the cross member. The 4 to the body were very tight and the one to the cross member i cranked only about a 1/4 of a turn until it was very snug. I didnt know what else to do so i lowered it down and took it for a spin and now everything is fine again :dance:



do you think that 1/4 turn could have stopped that clunking noise? It wasn't nearly as loose as i was expecting

[m3f_Sirius_880bd69485]

Who knows.. I doubt that 1/4 turn made it that loose.. but you never know.