KNOCKING NOISE FROM GEARBOX? IN LOW GEAR WHEN SLOWING DOWN

[Debbie Wilby]

Hi
I'm new to this forum - my last option for trying to find out what is wrong with my car.  It's been in garage a few times and even to a gearbox specialist but they are saying gearbox is fine and when i took into garage - mechanic took it for 30 minute drive and it did not make the noise.  However i picked it up drove it up the road and it started making it again - i'm at my wits end. 
It doesn't happen all the time and it is fine on long drives but if i am stuck in traffic in gear 1 or 2 an awful clanking noise comes from (i think) the gear box - sounds as though it is going to fall out.  This also happens when i slow down to park.
Has anyone else had this happen to their X3? OR does anyone know what it could be.  I'm sure mechanic thought i was making it up until my husband confirmed he has also driven it when it has happened.  I have recorded the noise on my phone!
many thanks

[Alan Gunn]

Are all the tyres the same.

[Debbie Wilby]

yes all tyres are the same and proper ones

[X5Sport]

Any warning lights?  Have you had either BMW or someone with an Autologic System check for error codes?  Autologic is/was used by Bosch Autocentres so a nearby one should be able to help confirm whether it is in the box itself or something else mechanical in the driveline - such as a bearing.

Is your specialist familiar with ZF transmissions?

Gearbox Oil levels OK - or at least checked?  Colour OK?  Should be clear and not dark, cloudy and burnt smelling?

Could be a diff, propshaft bearing, CVJ etc rather than the box itself.

kkx5 is our resident subject matter expert so may shoot me down as wrong suggestions and then come up with better ones - and I get educated 

[kkx5]

X5SPORT: 
Debbie: The noise could be from 4x4 transfer box. Remove fuse no26, test drive it and let us know.

[X3nut]

Just out of interest what would happen if you remove this fuse? Does it disengage the box and run on 2 wheel drive?

[Horizon]

Yes

[X3nut]

Great, might try that tomorrow as I have been told by a local Indy that the transfer case might need replacing because of a "knocking noise" at low speed. Have had this problem for around a year, the car had non  * rated tyres when we bought it so I replaced them with brand new pirelli's and seemed fine for a while.

[X3nut]

I've replaced this fuse and I have to say the knocking noise has gone and it seems a lot smoother. It doesn't even make the knocking noise when you go slowly around corners, does this mean that the transfer box needs replacing or is it a specific part within the transfer box?

[X5Sport]

Send a PM to kkx5 as he works on these systems, and repairs them.

[yes_its_neil]

If you haven't done so already, I would get the transfer case adaptions reset, especially if the noise is more obvious when turning. This can be done using DIS or INPA.

[kkx5]

Dis yes, Inpa no.