E92 m3 noise from rear...

[E21_Ross]

Hi guys,

Just a heads up as according to service manager at local bmw dealer its relatively conmon, an almost grinding like noise coming from the rear of the car under low speeds (usually) and cornering is to do with old diff oil. My dad just had the oil replaced under warranty. Car had gone 40k miles. Pretty sure he said they use slightly different oil now which is better. Takes about 2 weeks to get rid of the noise though for some reason.

Whether its a load of st or not I don't know but will see if it sorts it. I thought it was a wheel bearing or something!

Ross

Edit - forgot to add the noise was intermittent.

Edited by E21_Ross on Monday 13th June 22:12

[ecain63]

Yup, totally normal on M cars. Make sure the new oil is the expensive one with the FM Booster. BMW get it in on special order and it comes in a 3 bottle kit. Normally takes 400 to 600 miles to get rid of the noise. Nothing to worry about though.

[E21_Ross]

ecain63 said:

Yup, totally normal on M cars. Make sure the new oil is the expensive one with the FM Booster. BMW get it in on special order and it comes in a 3 bottle kit. Normally takes 400 to 600 miles to get rid of the noise. Nothing to worry about though.

That's reassuring. It was done by a BMW dealer so should be the good stuff. Should! He said it takes a couple of weeks for it to "soak in" apparently.

Thanks for that mate!

[derestrictor]

Hopefully this will cure my old Fünfic warhorse - also sounding like track 4 from British Steel when reversing into the i-Store car park.

[daz4m]

I'm not sure its anything to do with old diff oil, it was a common problem on the E46 models and I had it at around 20k on my Z4mc. There is an official tsb somewhere that says to replace with a modified formula.

[ecain63]

daz4m said:

I'm not sure its anything to do with old diff oil, it was a common problem on the E46 models and I had it at around 20k on my Z4mc. There is an official tsb somewhere that says to replace with a modified formula.

So what you're saying is, the problem is not the oil but if you change the oil it'll sort it? Confusing. Lol

The plates in the diff have a habit of sticking and then grinding under load, which is where the noise comes from. The oil with the FM Booster gets between the plates and stops them sticking.

[playalistic]

All the M diffs squeal on lock at slow speeds i.e parking manoeuvres. Apparently when servicing your car BMW won't specifically use the diff oil with the necessary inhibitor unless it is explicitly requested. Or so I was told by someone at Murketts anyway.

[daz4m]

ecain63 said:

So what you're saying is, the problem is not the oil but if you change the oil it'll sort it? Confusing. Lol

The plates in the diff have a habit of sticking and then grinding under load, which is where the noise comes from. The oil with the FM Booster gets between the plates and stops them sticking.

To clarify, I meant that it is not caused by OLD differential oil, on the E46, E85/86 anyway. It's really more of a gripe than an actual problem with the equipment.

This BMW bulletin refers (SIB 33 01 02), but some even say it's better to live with the noise than add the additive but not sure whether I support that view.

[krisdelta]

It does sound like it will be a diff oil replacement - the oil (it was 2.5 litres needed for the E46 iirc) was about £30 a litre and you need two replacement plugs for the diff (an extra couple of £).

May of course be different on the E9x but it's a well documented feature on E46's and is oft heard during low speed parking as previously mentioned. In my view £100 oil change is cheaper than a £1.5k diff!

It is possible there is a different FM booster oil for the E9x - your friendly dealer should know!