93 525i, 5 spd, on acceleration and deceleration there is a loud metallic ringing sound from underneath. Don't hear it when revving in neutral. Any ideas?
it's a ringing noise.... seems external, not muffled as I'd assume if it was internal to tran or catalytic conv. It's sounds almost like an old mechanical doorbell and is only evident when drive train is under stress.
You'll need to put it up on a lift and start wiggling transmission and exhaust mounts. Can't determine a ding based on forward and rear motion without getting under there.
I have experienced a similar sound initially when I bought My E34 that was unused for almost 6 yrs but kept in running condition. Have run pillar to post including the Exhaust repairers where finally the sound was rectified to be from Brake Disk and pad on the front right wheel. There are 2 shims on either ends of the pad to have a snug fit within the caliper, but somehow one of them was found missing which was allowing the pad to rattle and give this kind of a ringing sound on revving the vehicle to get in motion from stop. I am sure that this is your problem 99%.
This may be "pinging" under acceleration in ahigher gear with a load. Can happen if low octane or substandard fuel is used. This is also known as spark knock. Just guessing...
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