XSeries-forum

Hi all, I have an odd sensation that’s been happening recently.

When accelerating on medium/hard throttle, there is a loudish drone at 2.5k rpm (sounds like it’s from the front).
Yesterday I when I accelerated from 2k (in 5th) I noticed the revs slide up the 2.5k. (Same drone noise)

Something is definitely slipping - I had originally thought it was the clutch but then remembered that the pre facelift had a viscous transfer box - could it be that instead? Any way to tell or experience from on this from anyone else?

Cheer

If the clutch does start to slip then you’ll probably start to smell it before too long!

Ha yeah ok, good point! Are these the symptoms of a transfer box fail or 99% likely the clutch? Need to get it sorted before it fails but don’t want to do the clutch and find it’s not that!

There is judder if I don’t give it quite enough revs which makes me think it is the clutch

I’ve never seen anyone refer to a transfer box ‘slipping’ in the way you describe. Sounds more like clutch - and if it is then add a new flywheel too. I think BMW use a dual-mass flywheel and when our E46 was done in 2019 that was changed as well.

Cheers for the sanity check. Anyone know what the book time is to get it done? Best part of a day I’d imagine

Looking at the manual I would think a day is about right. The gearbox has to come off and that means exhaust, underbody protection and support structures. Lots of special tools shown as being needed as well (locking things and a compression device as the clutch is self-adjusting so needs to be correctly set up ‘as new’). No mention of needing a new flywheel (phew). All clutch fitting bolts and some jointing compound are listed as ‘must’ be replaced.

I'd say the flywheel is more likely than the clutch on my e46 it would lose drive at about 2k revs under load and the rev hand fly round to 4k with no drive
The droning sounds quite like the flywheel is getting more than it can handle and is starting to slip, they tend to rattle at idle when worn.