My '90 325i 5 speed had vibration on acceleration, until ~25MPH for as long as I had started driving it. It had been getting worse so I decided to take the plunge in dealing with it. Enter, hell.
Important to know: I set up a test-bed, where I have the car up in the air with the rear axles disconnected so I can remove some variables from the situation, as well as do some testing without having to keep going out and driving around. Also, my original driveshaft had the vibration damper on it, you know, the one that prevents you from running a DSSR.
I discovered the original driveshaft to have a very minute amount of play in the rearmost u-joint, my transmission mounts to both be severed, and the center support was no longer round?
This is mysterious to me, it doesn't seem like something that would've happened on its own...I can't decide if someones just goofed it up when installing it, or if this was an intentional move to align the driveshaft in a different way...
1) Installed first rebuilt driveshaft from Driveshaft Specialists in TX, with vibration damper. Vibrated like crazy above 50MPH Measured .025" of runout on the rear half of the driveshaft, which seemed excessive so I sent it back.
2) They send me a second one, fully custom-built unit this time. Install this one without the vibration damper though it has the wrong flange for the transmission, causing preload on the giubo, and more vibrations, though very different in frequency. Install vibration damper with this driveshaft so that it acts like a washer and takes the preload of giubo, then it gives me a high-frequency vibration. Back it goes.
Install the original driveshaft with the original damper, now that gives me a high-speed vibration, ok the damper is suspect, the rubber does appear to be separating from it so it doesn't seem unlikely. I run the original driveshaft without that damper and I get the least vibration of any driveshaft I've tried so far, but there is still a buzz at 50MPH.
3) Today I got the third driveshaft from them, another OE-style but rebuilt, slap it in and it vibrates at & above 50MPH, more aggressively than the original OE driveshaft, ugh.
Checked flange angles at diff and pinion, both are within a fraction of a degree, though my subframe does appear to be slightly higher than it should be because it's sliding on my subframe bushings? (f**** corteco bushings I swear)
Used a string to check for driveshaft straightness in the horizontal plane front to back, seems fine there as well, potentially ruling out the old CSB as an intentional play.
With the car "driving" at 55MPH on this remanufactured driveshaft and feeling around underneath for the vibration, it is 100% felt on the differential itself, not sure if that identifies the diff as an issue, or just the rear-most u-joint as an issue. Tried clocking the driveshaft 90 degrees on the pinion flange, not sure it really made a difference. Something I did notice is that the angle of the u joint at the center of the DS is 6 degrees off from the angle of the u joint at the rear of the driveshaft...trying to realign the two halves by separating them only puts them more off. Not sure how this would get messed up by them replacing u-joints though.
I'll be checking the diff flange for runout as a next step I suppose, then I push the car and its pile of driveshafts off a cliff.
Curious if anyone sees anything I'm missing. Otherwise I hope to chronicle this saga in case anyone else finds themselves in this hell. Fortunately all HPDEs and everything all are canceled, so I'm not missing out by not having a car :shrug:
Not trying to buy a new OE driveshaft for $1000, but that may be what it comes to. I just want to be super confident there's not something else going on with the car.
For reference, this is what my subframe bushings are doing as well: https://www.r3vlimited.com/board/for...jacked-replace
Important to know: I set up a test-bed, where I have the car up in the air with the rear axles disconnected so I can remove some variables from the situation, as well as do some testing without having to keep going out and driving around. Also, my original driveshaft had the vibration damper on it, you know, the one that prevents you from running a DSSR.
I discovered the original driveshaft to have a very minute amount of play in the rearmost u-joint, my transmission mounts to both be severed, and the center support was no longer round?
This is mysterious to me, it doesn't seem like something that would've happened on its own...I can't decide if someones just goofed it up when installing it, or if this was an intentional move to align the driveshaft in a different way...
1) Installed first rebuilt driveshaft from Driveshaft Specialists in TX, with vibration damper. Vibrated like crazy above 50MPH Measured .025" of runout on the rear half of the driveshaft, which seemed excessive so I sent it back.
2) They send me a second one, fully custom-built unit this time. Install this one without the vibration damper though it has the wrong flange for the transmission, causing preload on the giubo, and more vibrations, though very different in frequency. Install vibration damper with this driveshaft so that it acts like a washer and takes the preload of giubo, then it gives me a high-frequency vibration. Back it goes.
Install the original driveshaft with the original damper, now that gives me a high-speed vibration, ok the damper is suspect, the rubber does appear to be separating from it so it doesn't seem unlikely. I run the original driveshaft without that damper and I get the least vibration of any driveshaft I've tried so far, but there is still a buzz at 50MPH.
3) Today I got the third driveshaft from them, another OE-style but rebuilt, slap it in and it vibrates at & above 50MPH, more aggressively than the original OE driveshaft, ugh.
Checked flange angles at diff and pinion, both are within a fraction of a degree, though my subframe does appear to be slightly higher than it should be because it's sliding on my subframe bushings? (f**** corteco bushings I swear)
Used a string to check for driveshaft straightness in the horizontal plane front to back, seems fine there as well, potentially ruling out the old CSB as an intentional play.
With the car "driving" at 55MPH on this remanufactured driveshaft and feeling around underneath for the vibration, it is 100% felt on the differential itself, not sure if that identifies the diff as an issue, or just the rear-most u-joint as an issue. Tried clocking the driveshaft 90 degrees on the pinion flange, not sure it really made a difference. Something I did notice is that the angle of the u joint at the center of the DS is 6 degrees off from the angle of the u joint at the rear of the driveshaft...trying to realign the two halves by separating them only puts them more off. Not sure how this would get messed up by them replacing u-joints though.
I'll be checking the diff flange for runout as a next step I suppose, then I push the car and its pile of driveshafts off a cliff.
Curious if anyone sees anything I'm missing. Otherwise I hope to chronicle this saga in case anyone else finds themselves in this hell. Fortunately all HPDEs and everything all are canceled, so I'm not missing out by not having a car :shrug:
Not trying to buy a new OE driveshaft for $1000, but that may be what it comes to. I just want to be super confident there's not something else going on with the car.
For reference, this is what my subframe bushings are doing as well: https://www.r3vlimited.com/board/for...jacked-replace
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