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525i Vibration under Acceleration

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15K views 6 replies 3 participants last post by  witeshark  
#1 ·
Hello all...

I'm a first time BMW owner and this is my first post.

Recently I purchased a 2002 525i with the M54 engine, a 5 speed, and an M5 kit. It has 103K miles and looks and runs great. It has a new clutch, tires and brakes. During the test drive everything worked perfectly. Delivery of the car after the sale was a nightmare but that's a story for another day.

This car is a magnificent piece of machinery and I just love it. However, after driving it for a few months, I noticed one day that under acceleration I get a loud low frequency vibration from the rear of the car that you can feel in the seat and also in the shifter. It actually feels like something is banging on the rear floor pan.

The vibration and noise just gets more violent unless you let off the gas, after which it simply goes away. Needless to say I've been driving around very "gently."

My father took a look at the car for me and found the left rear wheel had about 1/4 inch of play. It turns out ( in his words) the rear wishbone between the sub frame and the top of the wheel carrier is shot at the ball joint where it connects to the wheel carrier. All of the play can be seen here when you move the wheel hub.

He is still checking the right side for other possible problems but so far we know the drive train seems very tight with no apparent play or noise in the drive shaft U-joints or the axle CV joints.

We'll begin the replacement process for the wishbone as soon as it arrives but I was wondering if this is a common problem and if this is indeed the source of the vibration.

Any insight from you experience owners would be appreciated. I will keep the thread going with our progress over the holiday.

Thanks in advance for your comments!!

Adam
 
#2 ·
[B]Problem Solved...Unbelievable!!![/B]

All of the forum insight regarding vibration due to drive shaft issues was right on the money. It was indeed the drive shaft flex link to the transmission tail shaft. In my case however, the looseness was not due to damaged components...rather the previous "mechanic" (and I use that term loosely in this case) that replaced the clutch plate did not properly install the connection bolts upon reassembly. When we got the car on a lift and took a good look, only one bolt, without a nut, connected the drive shaft flange to the flex joint (there should be 3), and again only one bolt with a loose nut connected the flex joint to flange of the tail shaft (again there should be 3.)

I was very fortunate the whole thing didn't explode apart!

I purchased new bolts (SBE 8.8) and locking nuts from NAPA for $27 but the garage had to cut them to the exact length. They are the red-coated bolts in the attached photo. The original bolt in the photo (black) was the lone remaining bolt holding the flex joint to the transmission tail shaft and it took a couple hours to get out since it was so deformed.

Total cost at the end of a 3 hour ordeal......$156.

Being able to accelerate again in my bimmer .........priceless!!
 

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#4 ·
Thanks!

I'm pretty happy too. Now I can move on to other less obnoxious sounds that I would like to eliminate (now that I can actually hear them) ...perhaps a bad wheel bearing or two.

I also learned while at my local garage, that the previous owner had mounted the wheels on the wrong side of the car...meaning the directional tires were rotating backwards. Sometimes you just have to wonder....

Still waiting for my "wishbone" to arrive.
 
#6 ·
Wishbone Replacement Follow-up

Well... we were able to replace the worn out Left Rear wishbone on my 525i and I just wanted to let everyone know that it was a very simple job. I used a Karlyn replacement piece (German made) that cost $57.44 including shipping, and the swap took about an hour.

As it turns out the Right Rear wishbone has some play in it also but not nearly as bad as the left. Nonetheless...it too is programmed for replacement.

In the process, I repositioned all of the wheels so that the tires were rotating the correct direction. That seemed to cut down on some road noise but two of the tires are cupped on the inside from the wishbone problems and I suspect I'm hearing some of that.

I've posted a pic of the new wishbone in place, and one of the old one with the 1/4 inch of play.

And now...off to the kitchen!!
 

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