What sound would a bad u-joint make?

[e34it]

I still have the sound in my M5, i think i have diagnosed it coming from under the car, towards the rear, it sounds sort of like a baseball card in the spoke of a bicycle wheel when i am on the throttle, anyone think it is a u joint? Would an O2 sensor make a noise if it was bad also? Im kinda lost here, gentleman? It only does it when im on the throttle, even in neutral or in gear in motion and sitting still, it doesnt seem to be effecting dirveability, any more ideas???

[Paul in NZ]

if it makes the noise when you are sitting still in neutral i would suggest some kind of exhaust leak

[Tiger]

How about loose cat converter heat shield?

[moots]

I still have the sound in my M5, i think i have diagnosed it coming from under the car, towards the rear, it sounds sort of like a baseball card in the spoke of a bicycle wheel when i am on the throttle, anyone think it is a u joint? Would an O2 sensor make a noise if it was bad also? Im kinda lost here, gentleman? It only does it when im on the throttle, even in neutral or in gear in motion and sitting still, it doesnt seem to be effecting dirveability, any more ideas???

howdy,
maybe my problem is related to yours.it's on the e30 however.manual tranny.
it makes the sound like you described,'cept the sound it more towards a knocking kind of sound and the frequency follows the car speed.and it makes the noise only without load(off throttle).this has been going on for 1 year and i was thrown off crs by thinking it's the differential.yesterday,i was under the car to fix the sloppy shifter and took the opportunity to identify the sound since the exhaust heatshield was off.i found out(at last) that the sound was from a loose U joint.strange as i could not fault it during earlier inspections ( by twisting the prop shaft).i haven't fixed it yet due to time constraints but hell am i relieved to have pin pointed the damned noise.(my wife drives the e30.i have the e34).hope this helps............

[632 Regal]

exhaust leak.