E9x M3 diff making loud grinding noise

[brother1]

Just had BMW emergency service round to listen to the noise that's coming from the back of the car when doing tight turns at low speeds. He confirmed that it is indeed the diff that's making the noise and that the car shouldn't be driven. Funny thing is (haha) I only just had the car serviced last week and the diff oil was changed. The car was absolutely fine before the service. If anyone has any ideas as I what might be issue, and help would be much appreciated. Am thinking I should get the car looked at by another dealership?

[Gruber]

Do modern LSDs still need the special additive in addition to boggo diff oil?

My guess is they've used the wrong diff oil, or forgotten the additive or not put enough in, or not tightened the fill-hole properly and it's all fallen out.... Or something like that.

Edited by Gruber on Thursday 22 December 18:55

[Nedzilla]

I seem to recall a few threads on this subject in the past.I think there is a different oil or an additive which should be added which cures the problem.I would've thought most main dealers should be aware of this by now though..Try doing a search see if anything comes up.

[ecain63]

The diff oil in question is the oil with 'FM Booster'. Its a specail part number and comes in a kit. A couple of hundred quid for the job at BMW.

[brother1]

Thanks for your responses guys, just found a thread that you also contributed to ecain63. Does this likely mean that the dealer put the wrong type of oil in the diff. If so, either the dealer made a basic error (how hard can it be!) or they're trying to cut corners by using the cheaper oil. Anyway, I've just re-arranged the car to be delivered to my other closest dealer in Blackheath, rather than the dealer where I recently got the car serviced. Hopefully they'll be able to tell me if a mistake was made or not.

This whole thing is stressing me out as Christmas is 2 days away and I have 750 miles of driving to do. Not sure if anyone has a multimac child car seat - great product - allows me to drive my average sized saloon with 3 small children, but is unfortunately not easily transferred to other vehicles and I have no other child car seats!!

[ecain63]

brother1 said:

Thanks for your responses guys, just found a thread that you also contributed to ecain63. Does this likely mean that the dealer put the wrong type of oil in the diff. If so, either the dealer made a basic error (how hard can it be!) or they're trying to cut corners by using the cheaper oil. Anyway, I've just re-arranged the car to be delivered to my other closest dealer in Blackheath, rather than the dealer where I recently got the car serviced. Hopefully they'll be able to tell me if a mistake was made or not.

This whole thing is stressing me out as Christmas is 2 days away and I have 750 miles of driving to do. Not sure if anyone has a multimac child car seat - great product - allows me to drive my average sized saloon with 3 small children, but is unfortunately not easily transferred to other vehicles and I have no other child car seats!!

Cant be sure if they made a mistake or not really. It is odd that its only occurred after the service so i'd be leaning toward that theory. Good luck mate.

Eddie

[brother1]

Thanks Eddie. Innocent until proven guilty I guess. Will let you know how I get on tomorrow.

[P101]

Dont trust a main dealer to do anything. Especially if their name begins with Sc Find a good indy.

[brother1]

Ok, as suspected the solution to the grinding noise is the use of the special FM booster oil. According to the dealer most cars are fine with the normal diff oil and hence all cars will have this oil added by default. However, some cars develop this grinding noise which I believe is related to the viscosity of the oil and those cars will therefore need the FM booster oil. I had to incur this cost myself as it is not covered by the warranty (£145 including vat and fit). My car will also need running in for up to 1500km with lots of 'left and right' turns before I can expect the noise to be eradicated, though the noise may disappear much sooner. The dealer where I got the diff initially serviced still believes the noise indicates something more serious, perhaps needing a proper inspection of the diff and potential replacement. We shall see. I still haven't got my car back however, as there was a seal missing from the diff which means it could now leak, and the dealer didn't have the part in stock, but this is unrelated to the grinding noise.
Thanks again to everyone for helping me out.

[Gruber]

brother1 said:

Ok, as suspected the solution to the grinding noise is the use of the special FM booster oil. According to the dealer most cars are fine with the normal diff oil and hence all cars will have this oil added by default. However, some cars develop this grinding noise which I believe is related to the viscosity of the oil and those cars will therefore need the FM booster oil.

I'm sorry but that sounds like BS to me. Surely all LSD cars need the FM booster, not just those that magically turn out to be noisy without.

Sounds very much like the dealer who did the original service has cocked up.

brother1 said:

I had to incur this cost myself as it is not covered by the warranty (£145 including vat and fit).

Presumably you'll be recovering this from the dealer?

[Zwolf]

Gruber said:

I'm sorry but that sounds like BS to me. Surely all LSD cars need the FM booster, not just those that magically turn out to be noisy without.

Sounds very much like the dealer who did the original service has cocked up.

Agreed. I'm very surprised to read that a dealer has used the same oil and aren't surprised you're getting a grumbly diff as a result. Why is the seal missing? That rings an alarm bell too. I'd be assuming at this point that the car was worked on by an unsupervised apprentice and certainly would not be happy footing the bill additionally for what sounds like their incompetence.

Suppose the diff had lunched itself - you'd be looking at several thousand I expect if you're out of warranty - and even if you're in, it may no tpay out if the wrong oil has been used, whether an indy fitted it or a BMW dealership.

Surely whichever service that mandates the diff oil be changed has that factored into the standard cost of that service (used to be Inspection 2, but I gather that's all gone now), so then asking you to pay extra for special oil seems wrong and like you're paying for their cock-up. Likewise if they've quoted standard model servicing cost for an M without accounting for the different requirements, then again, tough for them.

[E30M3SE]

Standard oil is Castrol SAF-XJ or Syntrax 75/140 as it is now known, the 'special oil' is SAF-XJ + FM booster, BMW part # 83 22 2 282 583.

It is possible to purchase the friction modifier from Opies for around £14 and just add it to your diff.

[MC99]

I had the diff noise occur after a day at Bedford autodrome, dealer did the diff oil under warranty. You shouldn't be made to pay "extra" IMHO

[brother1]

Some very good points guys. The fact that the seal was missing does suggest a mistake was made. As for whether the FM booster should be used for all cars is a question I need to ask BMW GB or some other dealers. It sounds odd that a 'hit or miss' approach to applying the FM booster is applied, especially when you consider that damage to the diff would indeed cost lots of money. I'm not sure BMW would be happy for dealers to be taking this approach as BMW would ultimately have to foot the bill for cars under warranty. All very fishy. I will have to make some calls on Wednesday but will let you know what I manage to find out.

[E30M3SE]

I would be more concerned if I had a LSD that was totally silent at low speed tight turns than one that casued a bit of noise, guess it goes against the more refined nature of the modern M car.

[brother1]

Picked the car up last Wednesday, £150 lighter, after having the FM booster oil added to the diff. After additional conversations with the dealer it does seem to appear that in most M cars the cheaper (standard) diff oil poses no problem for the diff and doesn't result in the grinding noise that I experienced on my car. Based on further research of other forums, it has been suggested that the grinding noise is the sound of the diff working as it should and that many people are comfortable with the noise. For the record, the noise has largely gone with the new oil and should go completely after another 800 miles of running in.

[ant man]

There should be a record of what was in the diff before, i.e. was the FM booster included or did it only have the diff oil?

Usually the grinding noise will go away after performing a number of 'figure-of-eights' at full-lock and in an empty car park and not require the FM booster.

Unfortunately you've experienced bad BMW service (not uncommon) and they should not have handed the car back it that condition without an explanation.

Glad it is being sorted.