odd thud sound

[grke36m3]

Hey guys just picked up my e30 a few weeks ago and been having a blast driving it until yesturday i started to hear a tapping sound that within 10 miles turned into a loud thud like something is hitting the rear center of my car. when i clutch in and put it in neutral the noise goes away. could this be my driveshaft or csb? i have a 318is do i have to drop the exhaust to get to it? thanks for the help guys

[Jaxx_]

is it only while accelerating? and yes, you need to drop the exhaust for either components.

[grke36m3]

Yes only wile in gear. Once I clutch in or put it in neutral it's gone.

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[AndrewBird]

I would say guibo and/or center support bearing.

[grke36m3]

Just ordered a new driveshaft with csb car has 220k so I'm sure ujoints are on their way out

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[grke36m3]

OK so i installed a reman driveshaft from driveshafts.com and im getting a vibration above 40mph and i can feel it in my seat. idk how i could of installed it wrong. i didnt separate each half to throw the balance off. i think my trans mounts are shot could that cause a issue with the driveshaft? anything i should check over to possibly help the situation? thanks for the help guys.

[grke36m3]

Could a un preloaded CSB cause a vibration above 40mph?

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[AndrewBird]

If the trans is shifted at all, it would put a bind on the driveshaft and cause a vibration. I'd start there.

Pre-loading might cause vibration, but I doubt it.

[Delta]

Check driveshaft phasing to be sure that the new shaft isn't out of alignment. Also make sure the CSB isn't installed backwards.

I installed a reman shaft from a reputable company and all of them vibrated until the 4th shaft was put in. Various issues between all of them.

[grke36m3]

well i have a update. i installed a second shaft from a reputable company and all is well no vibrations but 500 miles later the loud tapping sound is back. the original driveshaft had slightly choppy ujoints but the csb was fine. what could make this noise but disappear when i clutch in??

[grke36m3]

Could it be my axels? The CV boots seem fine. How can I check to see if they are bad? When I match the rpms with the wheel speed it kinda goes away.

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[grke36m3]

Ok a update. I jacked my rear end up to look around and didn't find anything unusual. Then I went for a drive and now the noise is gone. I guess by unloading the suspension it changed something?

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