XSeries-forum

My 2004 X3 (2.5 se petrol) has a terminal rear 'diff' failure which I am told is not worth repairing due to both cost (c£800 for reconditioned unit) & also the possibility that there may be issues further down the driveline.
My question is can I disconnect the prop shaft & run the vehicle as front wheel drive?
Look forward to receiving your advices.
Regards
JHK

I would get a second opinion. What tyres have you been using?

I am not sure I read it right but why is it not worth spending £800 to keep your car on the road?

The £800 is for a reconditioned 'diff' plus labour on top. It appears the 'fear' factor is that having effected the repair further problems may occur further down the driveline and no one will take the 'risk'. The car is worth in the region of £2.5k, however, having approached several garages & a 'specialist gearbox facility' no one will take on the repair.
As for the tyres, I changed the rear tyres a short while ago (land-sail) but not the fronts which were at 3/4ml. Been told since that the garage should have put the new tyres on the front wheels, also, there should only be a 3mm variance between front & rear wheel treads which was a contributory factor in the 'diff' failing.

Correct me if I'm wrong but these cars are rwd with the fronts added to make them 4wd.
If you pulled the prop nothing would work would it?

[quote="JHK"]
As for the tyres, I changed the rear tyres a short while ago (land-sail) but not the fronts which were at 3/4ml. Been told since that the garage should have put the new tyres on the front wheels, also, there should only be a 3mm variance between front & rear wheel treads which was a contributory factor in the 'diff' failing.
[/quote]

Unfortunately wrong tyres fitted altogether that has contributed/cause the problems you are now facing.
X3 (E83) needs '*' star tyres.

Have you had the car long?

[quote="MattX"]
Correct me if I'm wrong but these cars are rwd with the fronts added to make them 4wd.
If you pulled the prop nothing would work would it?
[/quote]

I think engine power goes to the transfer box then that dishes it out where it sees fit, via the Xdrive system inside the transfer box.
KK8 is the Guru on these systems as he rebuilds them for his Job.
I'm sure there was a post on here a while back from an E53 owner from Africa or somewhere that had a broken diff that had disconeced the drive shaft and feed from the transfer box to the bad axle, and was running around in it.
You will have to pull the fuse for the transfer box so it wasn't confused by inputs from sensors I suppose.
Be interesting to hear how you go on.

It's not recommended as you will affect things like the DSC as well. 

You will need to pull the fuse as a minimum and even then you still need a new diff as the axle still needs something even if it isn't being powered due to the driveshafts connecting through it.  The diff is there for going round corners as well as power delivery.  Simplest option is still a new one unfortunately.  If you are worried by things further into the driveline then the next item is the transfer box.

As you are now finding you need to change tyres as sets on BMW AWD cars as the transmissions can get 'wound up' by the difference in rolling diameters.  Eventually something breaks due to the stress.

This sounds pretty horrid as I've not experienced these tyre type/rolling diameter issues with Land Rovers or Audis so thanks for the advice:
Being new to the F25, do the rears wear faster than the fronts and presumably from what has been said, the larger diameter set should always be put on the front?
If axles are paired, would one normally expect only the transfer box to fail - presumably a rear diff failure would indicate different rolling diameters on that axle?
At what mileages do these issues start to manifest?
Would the dealer normally advise on tyre wear with transmission failures in mind or is it down to the owner to know about this?
My F25 was delivered (this week) with new fronts - presumably they go on the edges first at the front and centre at the rear?
Discoverys have a major transmission service (oils) at, from memory, 45k miles - Is there something similar on the F25? In fact, is there a mileage/age based service schedule to be found on the internet?

BMW transmissions are just not 'off-road' rated it seems.  Strange for what it touted as the 'Ultimate Driving Machine', but then they handle much better than most off-roaders.