Diff flange to DS flange orientation

[E30Gus]

Can the diff flange and the DS flange go on any way or is there a specific orientation?
Having slight vibrations after fuel tank R&R. Guibo, CSB, DS, and Diff all in good working condition and I didn't have this prior to the tank swap.

TIA
Gus

[jlevie]

When installing a drive shaft the only orientation that matters is that the drive shaft halves must aligned as they were when the drive shaft was balance. There should be a pain dot on each half at the center joint.

[E30Gus]

Thanks Jim,

Unfortunately this does not explain the problem I am having because I didn't pull the two halves apart. I don't know where to go from here....lost.

[jlevie]

Exactly what did you do in the process of swapping the tank?

[E30_fiend]

My guess is, whoever did the work didn't preload the center support bearing. If it wasn't preloaded, then it will shake as well as blow out VERY quickly.


Taylor

[E30Gus]

When I dropped the tank, I also removed the diff to reseal and put new fluid in it. The DS, exhaust, heat shields came out to get at the tank. I did preload the CSB and actually went back in there just to make sure. The only thing I can see as different than before is that the flange to the diff is rotated 90 from what it was before...i think. It's been a while since I've dropped the diff so I can't remember exactly. But I've never read that this matters. Other than that a new/used clutch fan was installed. I topped off the transmission fluid. My transmission mounts are in decent shape although a little bit squishy after ~3 years. Could having the car jacked up from the rear cause those mounts to shift at all causing the vibration? It isn't a BAD vibration but I'm pretty anal when it comes to vibrations especially when I want to get to the track real soon and I don't want anything bad to happen to ruin my weekend. At this point I have nothing to lose by rotating the diff flange 90 and trying that.

[Wanganstyle]

diff flange phase does not impact balance of driveline or cause vibrations.

my e30 is on custom diff test #4 as of this week and not a single time has the diff flange position been kept the same - different diff every time :)

[E30Gus]

After a week of driving, I am beginning to think the vibration is coming from somewhere else. It only happens over 85 mph and goes away ~95mph and has nothing to do with the engine rpm's. It almost feels like when a tire is out of balance or bad alignment and it starts shaking at a certain speed. I need to check the front suspension and go from there.
Anyone have GC camber plate bushings go bad and have to replace them? I ask because I've never changed them. I'm wondering if jacking the ass end of the car up for a couple days did something to loosen them up and cause this.

[jlevie]

That sounds like a slightly out of balance or out of round tire, possibly exaggerated by worn shocks or worn suspension parts. While worn bearings in camber plates are possible, they are unlikely to cause this kind of problem. Shocks, CAB's, tie rods, or control arms are candidates if you feel the vibration in the steering wheel. If you feel it in the seat, shocks, or RTAB's are the likely candidates.

[E30Gus]

Could a half shaft cause this?
While doing the swap I remember the drivers side shaft was ziptied up and at one point the zipties let go letting the half shaft drop down which I know is not good.
Should I swap the half shaft sides to see if anything changes?

[Wanganstyle]

no, the halfshaft will either be ok and working, or dis-coupled/pulled apart and not functioning. Halfshafts can have torn boots and missing grease but still wont cause vibrations.

check:

wheel bearings
bushings
top hats

check also anything that can vibrate free / moves / rolls?

[E30Gus]

no, the halfshaft will either be ok and working, or dis-coupled/pulled apart and not functioning. Halfshafts can have torn boots and missing grease but still wont cause vibrations.

check:

wheel bearings
bushings
top hats

check also anything that can vibrate free / moves / rolls?

All my bearings are fairly new and good. Bushings have all been replaced with poly within a few years.

How would the top hats cause this? I noticed that my pass side top hat spins easier than it has in the past and generally feels looser which is why I asked about the camber plate bearing. Please tell me more!

Thanks
G

[Wanganstyle]

if the spherical bearing is worn it will have nasty clunks yes. reference the entire rear end of FD3S mazda RX7 which had this issue due to oem spherical bearings in the rear suspension.