So, first with car on extended road trip. Some distance into the trip, I noticed what feels like an out of balance tire. The sensation comes and goes on a regular interval. So, I am concerned itay be something more serious. Transmission? Any ideas?

 

Did the vibration set in at any particular speed? Or on acceleration ... steady speed or coasting? Where do you feel it ... in the steering wheel or in the seat of your pants? It could be something simple like a wheel balance or a minor bend in a wheel.

Does it disappear if you slip into "neutral" at speed?? Could help determine if there is something in your driveline that is causing the vibration.

That said, it's been my experience that these vibrations are wheel and tire related. If you have a lot of miles on your tires they may have some cupping that isn't noticeable on your daily drive but sets up an annoying harmonic on long highway trips.

 

I recently purchased a 2004 525i, and mine does that also. Above 65 mph, I get vibration that lasts 6-8 seconds, then 6-8 seconds of non- vibration. I am amazed at the regularity. I feel my vibration more in the seat of my pants than in the steering wheel. In the Bentley service manual, there is a service bulletin r/t the driveshaft and universal joints. My car was delivered with 255-35-20 tires on Beyrern "5" rims. Falken up front and Nitto on the rear.

The first I will recheck is the balance and trueness of the wheels. Then the driveshaft. I am praying it is not the transmission, since the vibe (Harmonic Vibration as the another poster called it.) does not happen until I get to higher speeds; 70mph...at 65mph the car rides as smooth as silk.

If you solve this puzzle, please share your knowledge. And I will keep you posted on my progress. And believe me, I am going to solve this. It takes so much away from the road trips.

 

You exactly described my symptoms. I would think that a wheel/tire imbalance would result in a constant vibration not one that comes and goes on a regular cycle. Seems to be worse after driving awhile. I will have the wheels and tires checked as well and see what happens.

 

I did as Luigi suggested and slipped the transmission into neutral and it made no difference, the vibration continued. I also noted the empty passenger seat vibrating. Next stop, wheels and tires.

 

normally i'd think of the driveshaft as being the culprit. maybe your wheel bearings are getting some play in them. does the vibration go away if you turn the wheel slightly?

 

That is a hard to call Turbo, because I can't really turn the steering wheel at 75+mph. The Arizona interstates don't afford that. The part that fascinates me is the regularity of the vibration. This is my first BMW, and the fiftieth automobile in my lifetime. And I have never owned or driven a car that does this. I love my road trips and I fully plan the solve this!!!!!

 

i'm not talking turning a lot. does it occur when on a long curve? or when you do a lane change? i guess my point is, does it occur when the wheel bearings are loaded a bit..sideways.
if you dont have staggered wheels, how about doing a wheel rotation to see if anything changes?

 

Thanks again Turbo. I will make note of your suggestion. The interstates near my home on fairly straight. If a lane change is enough to load the bearings, that I can do. Thanks again.

 

Mine doesn't feel like wheel bearings. Going to dealer in morning for brake vacuum line recall. Will inquire while there.