[Bernard1973]

I've had my F36 in for some work under warranty and the health-check video has given me some bad news. I hit a large piece of cast metal that fell from a skip and it went under the car damaging the undertray - well I thought that was all but the video shows damage to the wheel (not too bothered - got a new set of 18inch alloys coming next week) but also a noise on the diff.
I'm going to have to see tomorrow what the cost will be to sort the diff, but I want to change the undertray myself. How can i find out the part number?
There is a part on ebay but it doesn't look the same? https://www.ebay.co.uk/itm/383023826036

https://video.citnow.com/vxdTznNW48z

[Abrek]

Surely diff is covered by warranty?

[Bernard1973]

Originally Posted by Abrek

Surely diff is covered by warranty?

Could the noise not have been caused by the object I hit?

[Abrek]

Originally Posted by Bernard1973

Could the noise not have been caused by the object I hit?

Couldn’t see physical damage to diff from video but I guess it’s worth pursuing.

[Bernard1973]

Originally Posted by Abrek

Couldn’t see physical damage to diff from video but I guess it’s worth pursuing.

Yeah you're right I can only try I suppose.

[TiredGeek]

I'd be doing a bit more than try.
I'd be wanting to see evidence that the damage to the diff has been caused by impact. If there's no damage to the aluminium casing then how can it be anything other than covered by warranty...…. massive gouge or dent then you're on thinner ice.
Undertray and wheel, no argument, but noise from the diff, don't let 'em try it on.

[Bernard1973]

Originally Posted by TiredGeek

I'd be doing a bit more than try.
I'd be wanting to see evidence that the damage to the diff has been caused by impact. If there's no damage to the aluminium casing then how can it be anything other than covered by warranty...…. massive gouge or dent then you're on thinner ice.
Undertray and wheel, no argument, but noise from the diff, don't let 'em try it on.

Cheers mate, do you know if there's history of problems with the diff?
It's done 19,000.

[999rigger]

I had a failed oil seal on my diff at about that mileage. Leaked oil over the drive.

[SteveChester]

Look on realoem.com should give you a part number.

[Pobsey]

Originally Posted by 999rigger

I had a failed oil seal on my diff at about that mileage. Leaked oil over the drive.

I managed to have 2 diffs replaced on one car (e87 120d) in 3 years, one at 60k and the other at 120,000miles both had bearing failures, so at 19k it should be an issue

[RobUK]

I'd be asking for the diff to be fixed under warranty. Could the dealer argue that the impact to the rear n/side wheel could have anything to do with it, like transferring shock to the diff via the output shaft, or is that just not possible?

[TiredGeek]

Originally Posted by RobUK

I'd be asking for the diff to be fixed under warranty. Could the dealer argue that the impact to the rear n/side wheel could have anything to do with it, like transferring shock to the diff via the output shaft, or is that just not possible?

Technically, yes, it could be argued that any impact to the drive line including the wheels could cause damage to any other component attached. It could, theoretically, have caused shock loading to the gears and bearings in the diff.

Shock loading is a real killer.
Think of wheels spinning on gravel then finding traction on the tarmac, the wheels are doing 1500 rpm then suddenly stop or drop 1000 rpm - you're throwing a couple of hundred horses and a load of torque towards the back axle, there's also the inertial weight of the components spinning around, suddenly stopping a wheel means all that energy has to be absorbed = shock loading.
Landrovers eat half shafts for breakfast with just this sort of thing.
BUT, having said all that, potholes, speed bumps, snow, basically anything that isn't billiard table smooth all have the potential to cause shock loads. The components are designed to withstand a certain amount of abuse without sustaining any damage..... just think of the shock launch control on a 335d gives the transmission!

To do the sort of damage that wheel has could have caused a shock load to the diff. Now Mr Stealer, show me the diff is damaged and not just a faulty component...…

[Bernard1973]

Well that was weird. I hadn't heard anything by 3pm (and this is the second day they've had the car) so I went in. I told the lad on the maintenance desk that I'd seen the video and that I'd known about the undertray and wheel damage but was worried about the comments about the diff. He looked confused and went to get the report and told me that there was no mention of anything wrong with the diff on the health report. He said they were still working on the car (sorting the parking sensors) and he would get them to check it.
I waited for an hour then he came over smiling and said everything was fine, there was no problem with the diff and that they wouldn't return the car to me if there was.
They had also changed the washer bottle as I'd said the washers weren't working, they gave me an invoice for £90 but didn't ask for payment?
I suppose that with the 15 month I've got left on the warranty it gives me time to make sure everything is ok.

The thing is, I can hear a noise on that video, is that normal?

[Dave-ncl]

I'm not expert but heard a noise too.

I'd take for a second opinion elsewhere once the underside and wheel are done.