[Reporter]

My 316i (1993) has been humming/droning from the rear over the last 6 months and is slowly getting louder. It seems to do it from about 40mph and not at very slow speed. Notice it more so if cruising at around 50mph, slightly louder if going up hill. I think the nosie is fairly central.

Reading through this great site, I managed today to drain the rear diff oil. Oil looks OK and was probably about 1 litre which I believe is the correct amount (1.1 litres).

What is the best oil to fill it with? I see 75/90 mentioned quite a bit but would be useful if someone could recommend a brand....I have some Castrol Hypo E90, is that the same?

If the new oil doesn't cure the noise, are the rear wheel bearings the next most likley?

Many thanks

P.S. BMW 316i 1993, 117,000 miles, diff oil never changed to my knowledge

 

[328mark]

does the noise alter when cornering?
might be an idea to get the bearings checked out either way

 

[Reporter]

Not noticed it alter on cornering. How do you check a bearing? Car has just passed MOT so would hope the bearings are OK. Do bearings hum/drone thought they would more likely click/rumble?

 

[badj]

The rear diff takes 900ml of SAE 90W gear oil. It will make a humming/drone noise if the wrong oil or incorrect level is in the diff.

If its a bearing it will cause a similar noise. to check it, jack up the rear, chock the front wheels, handbrake off and out of gear (so make sure front wheels are secure) -

Hold the wheel at the 9 and 3, then the 12 and 6 o'clock positions, checking for any free play. then rotate the wheel and listen out for any noises, any resistance, and anything but a smooth fairly free moving wheel.

Have fun!

 

[Reporter]

Great, thanks.

Any particular brand of gear oil recommended?

When checking the bearing, my car is Auto, does this also need to have N selected?

 

[badj]

yeah stick it in N
You'll still have the resistance of the shafts, diff and prop but you'll be able to tell the difference with a naff bearing.

As far as oil goes, go to bmw for it and get a price. id rather pay £10-£15 for BMW reccomended lube than halfrauds own brand rat pi$$

 

[Reporter]

Thanks again.

One more question, do I need to replace the diff plug metal washers or can I reuse? If I need new, do I have to go to BMW...bit of a trek!

 

[badj]

You're meant to replace them but I can never be bothered to! Should be fine

 

[slydog]

Hi reporter, my 328i auto is making the same noise that you describe, I too am at a bit of a loss as to what is causing it. The trouble with my car is that it does a very low anual milage. I plan to change my diff oil to see if it makes any difference. I'm pretty sure mine gets worse when the car has done about 5 miles of so, so the diff oil thinning as it warms up could be causing the prob. mine is v quiet at the moment and more noticable from the drivers seat than the passenger. Its also divided opinion among the people who have tried to diagnose it, some say wheel bearing, some diff , some central prop shaft bearing. please let us know if you crack it.

 

[xpress]

same here slydog, i am on the case with similar issue myself, will report back here.

 

[Ronnie]

Why not jack the car up onto stands then have a friend drive it in a high gear while you have a listen from side to side and underneath.

It is what most garages will do.