X3 3.0d auto box issues

[stabbed rat]

My parents BMW X3 3.0d has recently developed a nasty "clunk" in the gear box particularly in 1st + 2nd gear. I believe it is when the car is actually changing gear but I haven't checked yet (will aim to check tomorrow) just wondering if anyone knows anything about this kind of issue, is it FUBAR'd or (potential stupid question here) could be it anything to do with having fresh tyres on the front and dead (soon to be fresh) on the rear? Assuming a tread depth of 8/9mm when new and 2mm on the rear, that's quite a large circumfrance difference between the 2 sets on wheels.

Any help would be appreciated.

[TheEnd]

Tyre sizes can confuse it, you might see the traction light blinking at 70-80mph.
I take it you aren't getting any cog warning lights on the dash?

If it does have a problem, you'll probably get one thump of a gear change, followed by the gearbox cog light, and it'll stick in 3rd or 4th gear until switched off and on again.

[stabbed rat]

Thanks, I will get them to check at 70/80 tomorrow. It doesn't have any warning lights up so I can only hope it's not gearbox issues.

[TheEnd]

What might happen (ie has been seen on others) is the autobox on changing between 1-3, and nothing more by itself, although the steptronic bit will over-ride it into the higher gears.
That's usually a pretty good signal that it is unhappy with the road speed signal.

[stabbed rat]

I'm struggling to follow what you mean there, would the above cause sharp "thumps" as though the clutch was banging itself into place?

There is no traction control light on at any point and no cog warning light on the dash either.

Thanks for you help so far

[rassi]

Does this happen when accelerating, or when slowing down for the lights? What tyres are on the X3? Same size all round, or staggered (M Sport version)?

There are quite a few reported problems with the staggered setup, if the tyres are not the * BMW approved (235/50/18 and 255/45/18) and if there is a large difference in tyre thread on the front and rear axle.

[stabbed rat]

rassi said:

Does this happen when accelerating, or when slowing down for the lights? What tyres are on the X3? Same size all round, or staggered (M Sport version)?

There are quite a few reported problems with the staggered setup, if the tyres are not the * BMW approved (235/50/18 and 255/45/18) and if there is a large difference in tyre thread on the front and rear axle.

I will have to check with my dad later but I think it is both acceleration and deceleration. Will also need to check tyres, I don't think it is the M sport though.

[SBN]

I had this on my touring 330d, drove me crazy but only happened on the down shift from 2nd into 1st and would feel as if you had been rear ended. On the M25 in stop and start traffic it made my first experience of a BMW a horrible one!

However, i took it to BMW CARRS in Bury and after a quick check on the database this is a known issue and rectified with a simple software upgrade - AMAZING.

Car now drives superb and i love it to bits!

[stabbed rat]

I have driven it myself today, it's only on the up change from 2nd to 3rd and the tyres aren't staggered sizes (apart from the tread depth difference)