So last year I picked up an 89 325i automatic and basically went through the whole car mechanically and suspension wise and swapped in a getrag 260. Anyway, before doing any of this work the car was basically 100% original except some Bilsteins and Eibach springs and although the rear subframe bushings were pretty well gone I could easily take the car up to 90+mph without any noticeable vibrations. However after my swap I noticed a very a vibration coming from mostly the rear of the car but also seat feeling as well, it is a very high frequency and not related to wheel balance as it didn't exist before and I rotated the wheels front to back with no changes. Additionally it is seems largely irrelevant to engine speed and being on/off the throttle. The vibration can be felt slightly at around 75mph and picks up a bit with more speed, however it never gets so bad I feel it will actually damage the car short of maybe less u joint life. That being said, my 226k mile old subaru with original driveline seems to feel silky smooth vibration-wise compared to my E30 at any speed over 75mph which was not the case before the swap. I've had 4 newly rebuilt driveshafts in the car now, largely with the same exact problem so given they are all from reputable companies I do believe it's an engine/driveline alignment issue.
Below are the related driveline/suspension items I replaced all at the same time:
HD rubber Engine mounts w/ aluminum cups
HD rubber trans mounts w/ aluminum cups
the car has the correct OEM 5 speed stamped steel crossmember
garagistic 80a poly rear subframe and diff mounts (I had 2 other diffs in driveshaft #1, #2 , and #3 with rubber mounts, no change except for the speed vibration started, diffs were oem 4.10 open, 3.73 open, then finally 3.64 torsen now). The taller side is on top as per instructions
guibo (Febi) was literally almost new so I reused it for the for first driveshaft, I replaced it anyway with a new Febi one with the 2nd driveshaft with no change
new GKN CV axles - after driveshaft #1, made no difference but the old ones were starting to get bit of play anyway with 190k miles
new wheel rear wheel bearings - after driveshaft #1, no difference but replaced because they're old
Other notes: all driveshafts have the new nose bushing, grease, new CSB (none were cheap URO garbage). giubo is line up correct with arrows pointing at the flanges, all 6 bolts/nuts are the same, CSB was pre loaded as per the bentley manual in all installs, the first 2 driveshafts I tried rotating 180/90 degrees etc and nothing changed at all. Starting with the 3rd driveshaft I even got a laser to ensure the driveshaft was totally straight front to back, but main focus was the on both an up and down and left to right plane the front driveshaft is within .3 degrees of the engine/trans (digital angle finder, said to be accurate within .1 degrees or so). The engine, driveshaft sections and rear diff are no more than .5 degrees apart from one another (within bentley specs). Although I didn't check the first 3 driveshafts the max run out, on the 4th one I found after measuring in several spots of each section, run out was no more that .010" and nothing has any play which seemed okay to the shop and from my online searches.
driveshaft #1 - reputable TX company, noticed vibration around 60mph
driveshaft #2 - same company as above as above, switched to 3.73diff, speed jumped to closer to 70mph, then switched to 3.64 diff, maybe another mph or so more, driveshaft was returned as it was marginally better than the first vibration wise, they were cool about it since I am not close to TX to have them look at the car
driveshaft #3 - from a local company (20 min drive), said they would be able to help me diagnose if not the driveshaft, installed it, was basically same or marginally better than the TX company, but when asked they said they won't do this diagnostic service for BMW contrary to what I was told when I purchased the driveshaft, however they did return it without issue.
driveshaft #4 - I took my auto driveshaft to the company that rebuilt it as an auto under previous owner and they put a 5 speed section on the front and re-balanced, the auto driveshaft was almost brand new/freshly when I got the car. They said its probably not the driveshaft but alignment of it if it still vibrates after. I installed it and the vibration was slightly less but was starting to be noticeable at 75mph (before with the others it was 60-70ish depending what rear was with it, so this one was a bit smoother). I think they were all probably the same, its just I was super attentive to the driveshaft alignment because I had taken apart and double check so many things. I took it back to them to have them check the alignment and they said everything was good and nothing to adjust (focused on the front mostly where adjustment can easily be made, however they looked at it all supposedly) They were actually surprised how close I had gotten it myself. The owner recommended I try adjusting the pinion some to see if it helped but I didn't notice any changes (pinion down 2 degrees further using washers, I tried about 4 iterations to get this and none helped, some made it worse, especially at 2 degrees, but marginally so)
At this point its okay enough as I can cruise at 80mph and not be too annoyed with just minimal vibration, but I still don't feel like this issue is resolved and even a very reputable shop couldn't diagnose it. I even spend $100 on this driveline vibration app and it flagged only one thing, driveshaft vibration lol. Does anybody have any idea what could be causing this vibration or any potential things to check? I have never spent so much time and money trying to diagnose something like this with essentially no results or without finding anything I did wrong, or part out of spec, etc. Feel free to ask for any further details on what I have attempted to explain above too.
Thanks for reading, I feel like this is a novel at this point.
EDIT: cleaned up a few typos
Below are the related driveline/suspension items I replaced all at the same time:
HD rubber Engine mounts w/ aluminum cups
HD rubber trans mounts w/ aluminum cups
the car has the correct OEM 5 speed stamped steel crossmember
garagistic 80a poly rear subframe and diff mounts (I had 2 other diffs in driveshaft #1, #2 , and #3 with rubber mounts, no change except for the speed vibration started, diffs were oem 4.10 open, 3.73 open, then finally 3.64 torsen now). The taller side is on top as per instructions
guibo (Febi) was literally almost new so I reused it for the for first driveshaft, I replaced it anyway with a new Febi one with the 2nd driveshaft with no change
new GKN CV axles - after driveshaft #1, made no difference but the old ones were starting to get bit of play anyway with 190k miles
new wheel rear wheel bearings - after driveshaft #1, no difference but replaced because they're old
Other notes: all driveshafts have the new nose bushing, grease, new CSB (none were cheap URO garbage). giubo is line up correct with arrows pointing at the flanges, all 6 bolts/nuts are the same, CSB was pre loaded as per the bentley manual in all installs, the first 2 driveshafts I tried rotating 180/90 degrees etc and nothing changed at all. Starting with the 3rd driveshaft I even got a laser to ensure the driveshaft was totally straight front to back, but main focus was the on both an up and down and left to right plane the front driveshaft is within .3 degrees of the engine/trans (digital angle finder, said to be accurate within .1 degrees or so). The engine, driveshaft sections and rear diff are no more than .5 degrees apart from one another (within bentley specs). Although I didn't check the first 3 driveshafts the max run out, on the 4th one I found after measuring in several spots of each section, run out was no more that .010" and nothing has any play which seemed okay to the shop and from my online searches.
driveshaft #1 - reputable TX company, noticed vibration around 60mph
driveshaft #2 - same company as above as above, switched to 3.73diff, speed jumped to closer to 70mph, then switched to 3.64 diff, maybe another mph or so more, driveshaft was returned as it was marginally better than the first vibration wise, they were cool about it since I am not close to TX to have them look at the car
driveshaft #3 - from a local company (20 min drive), said they would be able to help me diagnose if not the driveshaft, installed it, was basically same or marginally better than the TX company, but when asked they said they won't do this diagnostic service for BMW contrary to what I was told when I purchased the driveshaft, however they did return it without issue.
driveshaft #4 - I took my auto driveshaft to the company that rebuilt it as an auto under previous owner and they put a 5 speed section on the front and re-balanced, the auto driveshaft was almost brand new/freshly when I got the car. They said its probably not the driveshaft but alignment of it if it still vibrates after. I installed it and the vibration was slightly less but was starting to be noticeable at 75mph (before with the others it was 60-70ish depending what rear was with it, so this one was a bit smoother). I think they were all probably the same, its just I was super attentive to the driveshaft alignment because I had taken apart and double check so many things. I took it back to them to have them check the alignment and they said everything was good and nothing to adjust (focused on the front mostly where adjustment can easily be made, however they looked at it all supposedly) They were actually surprised how close I had gotten it myself. The owner recommended I try adjusting the pinion some to see if it helped but I didn't notice any changes (pinion down 2 degrees further using washers, I tried about 4 iterations to get this and none helped, some made it worse, especially at 2 degrees, but marginally so)
At this point its okay enough as I can cruise at 80mph and not be too annoyed with just minimal vibration, but I still don't feel like this issue is resolved and even a very reputable shop couldn't diagnose it. I even spend $100 on this driveline vibration app and it flagged only one thing, driveshaft vibration lol. Does anybody have any idea what could be causing this vibration or any potential things to check? I have never spent so much time and money trying to diagnose something like this with essentially no results or without finding anything I did wrong, or part out of spec, etc. Feel free to ask for any further details on what I have attempted to explain above too.
Thanks for reading, I feel like this is a novel at this point.
EDIT: cleaned up a few typos
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