‘88 325is vibration between 55kph-80kph

[saskye30]

A while back I did rear subframe bushings, trailing arm bushings, transmission output shaft seal, selector rod seal, guibo, and csb. Car was driving great except for a new noise a whine that would start at 40kph. The diff was done and figured the noise was the diff. Now have a used diff installed and the whine noise was still there.

Yesterday I changed the csb with an oem one and the noise is gone, but now once you hit 55kph there’s vibration until 80, then it goes away until you decelerate thru that.

It was butter smooth before but was whining now it’s silent except for the vibration. Before I crawl under the thing in the cold garage, hope I might get some knowledge of what to check.

Thanks in advance. I’ve poured a lot into it and mechanically this is the only thing she needs (for now haha)

[Sea Aych]

Did you "pre-load" the CSB by nudging it forward 5mm-ish when you bolt it up?

Also, how are your rear wheel bearings? I was going to suggest diff (because i had the same symptoms as you), until i saw you changed it.

[packratbimmer]

I had a similar problem when I used a cheap CSB. problem gone after replacement. What brand did you use?

[Kershaw]

Maybe recheck your tires too.

[MrBurgundy]

Maybe recheck your tires too.

yeah, sounds like it may be some unbalanced tires.

[tomstin]

A lot has been mentioned but:
Move the tires front to back and see if that changes anything. You could be chasing your tail. Maybe have the tires road forced balanced. That surfaced a out of round rim for me.

Are you sure you installed the flex bushing (guibo) correctly?
Pre-load the Center Support Bearing?
Properly match up (align the marks) the two pieces of the drive shaft when you replaced the CSB?
Properly tighten the threaded collar on rear section of the drive shaft?
Did you check the u-joint when you took the drive shaft out?

Align the whole mechanism? I wrote up a post on the DIY section that may help. In a nutshell, I used fishing weights hanging from strings to make sure from the front of the engine to the differential everything was aligned.

I just got finished chasing a vibration. Out of total frustration, I ended up buying a rebuilt Beyer driveshaft that solved 90% of my vibration after having a local guy rebuild and balance my driveshaft. The other 10% ended up being a front strut bearing of all things!

Good luck, vibrations can be tough to track down...and god I know how frustrating!!!!!