Chassis/cabin vibration at highway speeds only

[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 :)

[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]

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.

[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]

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.

[cory58]

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

[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.

[glnr13]

watching and subscribing, i have the same symptoms.

[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.

[Westija]

Long shot, but let's assume you have a bad rear tire. One way to eliminate that would be to swap rears with fronts and see if the vibration comes to the steering ?

[Mozza1219]

Long shot, but let's assume you have a bad rear tire. One way to eliminate that would be to swap rears with fronts and see if the vibration comes to the steering ?

I think i've already swapped the wheels around but i can't remember so I'm going to try that today. Also going to try and back the handbrake off a little more as I recently replaced the shoes and didn't really understand how tight it was. I'll report back with my findings.

Interestingly, the vibration has changed a bit, the range at which it vibrates is now bigger, it seems to vibrate beyond 70mph, but the frequency of the vibration is at its worst at 60mph, which is why its more noticeable at that speed.

UPDATE: swapped the wheels from front to back, no change.

[twright]

You need to find out if your wheels are bent. Just because two different shops balanced them, it doesn't mean that they might not be bent. (you can balance an egg, but it won't roll very well)

The way I check wheels is too jack up each wheel and spin them by hand. If they are really bent, you can see it right away. If they are only bent a little bit (1/16" is too much), you have to place something on the ground next to the rim (scissors jack?) so you can see if the wheel moves in relation to your reference point (scissors jack).

You can chase vibration problems forever with a bent wheel. Those have to be straight. Don't let the tire guys tell you to just put them on the rear. That won't work if you want it smooth.

[Mozza1219]

You need to find out if your wheels are bent. Just because two different shops balanced them, it doesn't mean that they might not be bent. (you can balance an egg, but it won't roll very well)

The way I check wheels is too jack up each wheel and spin them by hand. If they are really bent, you can see it right away. If they are only bent a little bit (1/16" is too much), you have to place something on the ground next to the rim (scissors jack?) so you can see if the wheel moves in relation to your reference point (scissors jack).

You can chase vibration problems forever with a bent wheel. Those have to be straight. Don't let the tire guys tell you to just put them on the rear. That won't work if you want it smooth.

Thanks twright.

I'll try and get my hands on a set of different wheels and see if it's any better.

But since I swapped the wheels from front to back, if a bent wheel was the culprit, wouldn't the vibration move into the steering wheel?

[twright]

Thanks twright.

I'll try and get my hands on a set of different wheels and see if it's any better.

But since I swapped the wheels from front to back, if a bent wheel was the culprit, wouldn't the vibration move into the steering wheel?

Not if you have two bent wheels.


Jack up the car and spin the wheels. It's the only way to know if they are straight, and it doesn't take very long to do.

[TobyB]

I'd suspect something went wrong with the driveshaft remanufacture.
Check the caps on the joints to see if they all protrude from the yokes the
same amount, then see if there are any shiny spots where a weight might have
flung off.

You can stick a little camera and a light down there, and see what it's doing at speed.

I've had numerous driveshaft vibes, and yes, the cabin resonates in a way that
you start to recognize after a while.

hth

t