Chassis/cabin vibration at highway speeds only

[Mozza1219]

watching and subscribing, i have the same symptoms.

Excellent.
I'm starting to think it's the rear wheel bearing, but I've never known bad bearings to actually vibrate the whole car.

[glnr13]

watching and subscribing, i have the same symptoms.

[Mozza1219]

Have you tried changing the preload of the CSB, to see if the vibration characteristics change?

Yeah, I had it on no preload before, when i checked all the driveshaft bolts etc I preloaded it. No change.

[cory58]

Have you tried changing the preload of the CSB, to see if the vibration characteristics change?

[Mozza1219]

double check you have all the bolts in the flex disk, as well as the diff flange. Also, make sure diff mounts are tight.

Checked all the bolts again. No change. This is really bugging me.

[Jaxx_]

double check you have all the bolts in the flex disk, as well as the diff flange. Also, make sure diff mounts are tight.

[Mozza1219]

Well if you suspect the driveshaft did it after the unis, then maybe when you did the unis you through the balance out of the driveshaft. I had a drive shaft checked for balance at the local driveline shop a few yrs back, was less than 100bucks. might be worth looking into if you cant find anything else (or nobdy else has any good ideas)

I don't know if I suspect the driveshaft. What I meant was, I had the driveshaft uni's replaced and the shaft was apparently balanced. I installed it, all good. Then a few weeks later this vibration started.

[e30davie]

Well if you suspect the driveshaft did it after the unis, then maybe when you did the unis you through the balance out of the driveshaft. I had a drive shaft checked for balance at the local driveline shop a few yrs back, was less than 100bucks. might be worth looking into if you cant find anything else (or nobdy else has any good ideas)

[Mozza1219]

Hey guys i'm after some assistance with a problem which my e30 (323i) has recently developed.

The car gets this bad cabin vibration (bottom of seat, nothing in steering wheel) when driving on the highway (55mph to 70mph), but ONLY in this speed range. Outside this speed range, the car is perfectly smooth.
Being in neutral, accelerating, braking or steering in either direction doesn't have any affect on the vibration, it is only occurring in the above speed range. This leads me to believe that the issue is from the driveshaft and further back (CV's etc).

Things I've done so far:
1. New driveshaft Uni joints, giubo (made sure it was facing the right direction) and CSB installed (CSB could probably be pre-loaded more, but I don't see how this could cause this bad of a vibration?)
2. Tyres have about 200 miles on them (balanced twice at two different shops now)

I changed the driveshaft Uni's because I was experiencing another issue which ended up being a misfire (uni's were pretty stiff anyway). But I swear that when I originally installed the driveshaft, this vibration did not exist. It only started occurring sometime after I had the car running well and i noticed it when i was driving on the highway.

Any help would be appreciated! Thank you :)