Well, after about two hours of searching and reading vibration threads I don't feel much closer to an answer of even where to start looking or how.
My car is a completely stock daily driven 1991 325i convertible automatic. 175k in very good condition. I've owned it since April 2017. There have been no repairs or changes to the driveline or suspension since I've owned it.
I don't know if it is related, but I had a vibration that started out intermittent. Over about five months I would have one or two instances during a month where i'd have a mild vibration/shake from 0 to about 30 MPH. After about 2-3 miles it would go away. Again, just once or twice a month for a mile or two.
My current issue. Starting at about 40 MPH, quietly a hum starts to be audible. It's subtle at that speed, but if I'm concentrating I can start to hear it then. I can't feel it in the steering wheel. It's speed dependent. By 70 MPHI can hear it pretty easily with the top up, still to quite to hear with it down. It isn't loud, but it isn't the normal sound I know from previous months driving the car. I'd peg the hum around 500-700hz at 70. The side mirrors blur cars behind me visibly showing the vibration. It is hard to localize and almost feels central in the car. It does not increase or change when turning. (Lets be honest though, I'm not doing much 70 MPH cornering in my stock convertible! :) )
It isn't like a hard vibration from an unbalanced tire or such. I know what those are like. There isn't any shaking.
I'm just kind of stumped at what this could be or where to start, and I haven't found anything that really sounds like what I'm talking about in the posts on here.
My car is a completely stock daily driven 1991 325i convertible automatic. 175k in very good condition. I've owned it since April 2017. There have been no repairs or changes to the driveline or suspension since I've owned it.
I don't know if it is related, but I had a vibration that started out intermittent. Over about five months I would have one or two instances during a month where i'd have a mild vibration/shake from 0 to about 30 MPH. After about 2-3 miles it would go away. Again, just once or twice a month for a mile or two.
My current issue. Starting at about 40 MPH, quietly a hum starts to be audible. It's subtle at that speed, but if I'm concentrating I can start to hear it then. I can't feel it in the steering wheel. It's speed dependent. By 70 MPHI can hear it pretty easily with the top up, still to quite to hear with it down. It isn't loud, but it isn't the normal sound I know from previous months driving the car. I'd peg the hum around 500-700hz at 70. The side mirrors blur cars behind me visibly showing the vibration. It is hard to localize and almost feels central in the car. It does not increase or change when turning. (Lets be honest though, I'm not doing much 70 MPH cornering in my stock convertible! :) )
It isn't like a hard vibration from an unbalanced tire or such. I know what those are like. There isn't any shaking.
I'm just kind of stumped at what this could be or where to start, and I haven't found anything that really sounds like what I'm talking about in the posts on here.
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