I've fixed many a drive line noise before, and this one has me stumped. To breifly explain, the clanking noise started after a spirited drive with a friends Z06 last Summer. In Sept 09, the car developed a clicking, tapping on the driveshaft sound when accelerating hard or decelerating hard. The intensity of the noise changes with engine load. When barely accelerating, as done by the cruise control + key, the noise is barely there. For the few miles the car has covered since the development of the noise, it has been very difficult to acclerate at all without some noise present. The interval between the tinks changes with wheel speed/driveshaft speed, and is not related to gear engaged (happens in all gears forward and reverse). The only exception to this is that driveline torque is much greater in lower gears than higher gears, i.e. when you press 1/2 way down on accelerator in 2nd gear, the noise is very loud; when you press 1/2 down while in 5th gear, the noise is not as loud; I presume because the driveline is not under the same load.
I started to think that the rear CV on the driveshaft was causing this, and the loud tink tink noise is due to the resonating through the hollow driveshaft. If you have ever removed a BMW driveshaft and knocked the wrench on it accidently while unfastening the guibo, you know the pitch I'm talking about.
So last September, I put it on the lift to inspect the situation. I found 6 loose rear CV bolts, Most of them were between 1 turn and 2 turns from full torque spec. As the nuts were replaced when the joint was replaced, I expect that I failed to meet the torque spec, which is hard to do, as a crowsfoot is required to make them tight. After I got that sorted, I figured the problem was fixed. I put the exhaust back on and went for a test drive. Noise still there.
I parked the car for 1 month; bought an 01 740IL as winter was approaching. Figured I would deal with the problem after winter.
Fast forward six months to last night. Drove the car home with no noise in the driveline whatsoever 3/22/10. No tink, nothing... Took it very easy, as if the car still had the problem. I did my best to not exacerbate the issue, and succeeded.
This morning, 3/23, went to work. No noise until the last 1/2 mile of a 5 mile long 45 MPH commute. Tink ,tink, tink, etc. Seemed to only do it when turning left or right (which makes NO sense at all).
After work, car was tinking on all acceleration and deceleration. Total mile driven since first hearing the noise in Sept 2009 is probably 15 or so.
I recorded the ride home tonight with my iphone sitting on the rear driveshaft hump in front of the rear seat. Take a listen real close, and see if you think a driveshaft replacement will fix this issue.
I need to get this fixed, as I just got it out of the garage after a 6 month hibernation. For some reason, it didn't fix itself while it was in storage
Any ideas would be AWESOME.
Car is an 03 M5, 88,000 miles.
Service History (Related to Driveline)
77,000 miles - New Flywheel/Clutch, Driveshaft Center Bearing, and Rear CV Joint on Driveshaft, and Guibo. New Diff Bushings.
Moving back and forth in my driveway
Driving through the subdivision, no faster than 25 MPH, taking it easy.