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Weird rear end thump


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So starting a couple weeks ago I began to have a problem with something in my cars rearend thumping and shaking the whole car. It happens about 18 mphs in all gears so it's not the center bearing. It also sorta happens about highway speed but not as bad. When it's at 18 it's semi violent like your going over washboards but over 20 it's gone and under 15 its gone. So what do you guys think it is, I have absolutely no idea. IE Sway bar out of adjustment, bad half shafts, bad guibo, bad ?? The tires were balanced recently to hopefully stop this problem and it didnt... So what you guys think?

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Guest Anonymous

you could swap the tires front to back to rule them out, but that is pretty low speed for a tire to cause problems. The fact that it happens at the same speed, not the same rpms, means it could be anything from the tranny back. Include the shock mounts in your inspection.

One easy way to localize it would be to put it on a lift and run it.

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if the guibo is anything but pristine, replace it!

Good thing I have a spare one from my 320 parts car... I'll get on replacing that one here soon.

If it turns out to be the differential mount, I've got a couple in the junk pile you're welcome to. Good Luck.


Thanks Ryan, I'll check and get back to ya on that!

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Well, I jacked it up, put it on stands and ran the car in 4th at the thumping speed. I found out my center bearing has gone soft and it's now wobbeling a good 1/4 inch... Time to replace that guy. By chance does anyone know if a 320i 4 speed driveshaft will fit? I have an almost new one of those with an almost new center bearing & guibo...

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