Need Help Diagnosing a Severe Vibration at highway speeds

[Metroporter]

I just replaced the drive-shaft on my 1997 328i automatic. The new drive-shaft came fully assembled & balanced. It also included a new center bearing support & nose bushing. Aside from a new flex-disc / guibo, it was a simple bolt-on procedure. I got everything put back together and drove it for a couple days with no problems - in fact I can't remember the last time it drove that smoothly.

I then took it to a local tire shop for a rotation & balance of the tires. As I drove home, I noticed a slight vibration as the car passed through ~50mph. Otherwise, no problems. On a second drive, later that day, the vibration was a bit worse. Third errand: it was out of control. I coasted down from 65mph and eased on the brakes as I hit the exit ramp and I honestly thought I was going to lose control of the vehicle. I immediately released the brakes and the vibration only subsided with a reduction in speed

A) The first thing I thought of was the lug nuts - they were all tight. B) I've now removed the wheels and checked all of the suspension components - everything there seems to be in good repair. C) I dropped the exhaust (with heat shield) for an inspection of my drive-shaft work - all appears to be in good order from the flex-disc, all the bolts are tight, the center bearing is tight, the balancing-welds on the drive-shaft are all in place... I am at a loss! Any suggestions would be greatly appreciated!

[Manolito]

When the ball joints on these cars get loose, they can find a resonant frequency at certain speeds and make the whole car shake. If the new drive shaft is tight and the lug nuts are tight, I would be looking at ball joints.

If they are original and the car has over 100k miles, they are due.

It is possible to press out the existing ball joints and press in new ones, but you need a big hydraulic press or the special BMW tool. Almost everyone just buys the control arms with new ball joints already installed. You need to replace the control arm bushings along with the control arms.

[Metroporter]

Thank you for the response! How might I confirm that it is, in-fact, the ball joints?

[Manolito]

Checking worn ball joints is not as easy as you might expect. You can jack up the car and put it on jack stands, and then grab the top and bottom of the front wheel and jiggle it. Any play you feel will be either the wheel bearing or the ball joint, and it is pretty easy to distinguish which. The problem is that when the front wheel is dangling, the ball joint is at a much different angle than it is at normal ride height. It might be sloppy as heck at its normal angle, but tight when pulled over at a sharp angle when the wheel is dangling.

If you had a professional wheel alignment rig, you would put the wheels on those "pizza tin on marbles" plates that they have on the machine. Then you could pry on the wheel or joint at normal ride height.

You can run the car up on ramps with the weight on the wheels try prying up and down on the ball joint with a big screwdriver and a block of wood to see if you can get it to move. A few thousandths of an inch is normal, but movement of the joint that you can see or feel through your big screwdriver, up and down or side to side, is unacceptable.

[traction issuez]

You should get the wheels rebalanced by the shop that did them and go from there, improperly balanced wheels will do this.

[Metroporter]

Thank you both for the advice! I went ahead and replaced the control arms. Both ball joints were loose (easily manipulated by hand) but the outside ball joints had visible play in them just moving them by hand. 215k miles = way overdue! Now with the new control arms (& bushings), and a new alignment, it seems to have resolved the issue. Thank you again!