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BMW e46 320i whining noise from rear - louder in 5th gear

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e46 noise whine
683 views 3 replies 3 participants last post by  andersp 
#1 ·
Hi e46fanatics,
I have a E46 sedan 320i m52tüb20 1998. I have this slight but noticeable whining noise from the back. When on the throttle you can barely hear it at all, but as you come off the gas (engine braking) the whine becomes louder. I have also noticed it is louder around 40-60km/h (25-40mph) and/or when in 5th gear. It could also just sound louder because the engine is at lower RPM in 5th(and less overall noise at that speed), but I swear it's louder.
Oil in gearbox and diff were changed and didn't do anything.

What could be the cause of this?

Regards,
Anders P.
 
#2 ·
Next to check is that the bushings are all ok- if they fail, more noise can be transmitted
into the cabin by hard rubber- to- rubber contact, or even metal on metal.
The diff moves around based on loading, so that can change with throttle.
Also, see if the exhaust is touching it, or any part of the subframe. It can act
as an emitter, and also moves quite a bit.

If you want to hear it a lot more, just pull out the rear seat!

The other likely explanation is that the pinion bearing in the differential
is worn and/or loose, and the pinon has started to move around a bit.

t
 
#3 ·
What oil did you use in diff? What's the mileage on the car? The bushings can be bad as Toby said, but also the diff can be worn out. My diff bushings are in top condition (new) and the diff whines more than the previous did, because I swapped it (on the same bushings) It's due to different backlash and wear.
 
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