BMW doesn't speak diagnosglish

[Xited]

Hi everyone

First time poster, long time lurker. I've really enjoyed reading the various posts on this site - not only knowledgeable but really down right helpful and nice. This is a great forum.

Bit of a story to my intro / car. Feel free to skip to the bottom if you just want to get to the question but if you're reading this and are in two minds about whether or not to get a car checked before purchase, then read it all.

I've just taken posession of a (new to me) 2004 X5 3.0d (6 speed auto box)

I actually purchased this car about 6 weeks ago - flew up from Melbourne to Queensland to pick it up. Plan was to drive it down to Melbourne (approx 2000km) so told the dealership the car had to be in good nick. Was told the car was perfect and that they would never sell a car unless it was really good (they are a big Mercedes dealership so only stock good cars that have been traded - they wholesale the rubbish stuff).

So i pull out of the dealership at around 8pm and head towards Brisbane (approx 150km away). Within 3 minutes - literally - the Trans Failsafe Prog message comes up - no thumping from the box or anything, just the message. I call the dealer and ask him what's going on - this car is meant to be good. He gives me some nonsense reason that car has been sitting for a while, sure is just a sensor fault, turn it off and turn it back on again. Sure enough, error disappears and hesitantly i continue my journey.

In the morning, i'm tossing up between driving the car or taking it to get checked out. I decide to take it to a BMW dealer to do a diagnostic. Response: needs a new gearbox. I'm like what? It drives fine... he tells me the error code is 4F51 EGS: 5 Gear monitoring & IKE: EGS signal line disturbed and says that it means the transmission is slipping and that the clutch packs are worn. He also said they analysed some of the oil and it was burned and had stringy bits in it.

So i call the dealership and tell them and after much hassle they tell me to drive it back up - another 150km. Long story short they took back the car and refunded the money - BMW quoted $11k for a new transmission and they were not prepared to pay.

I get back home and begin my search again and can't find anything. Well, out of the blue the dealer calls me back and offers me a ML63 and a '09 X5 - both way out of my price range. Then he says, you know, we still need to get rid of this car and can't sell it with a problematic transmission - if we fix it, would you be interested (they also wanted more than i paid first time around as they were fixing the 'box). I said no as i would have no warranty from 2000km away and would only consider it if they dropped the price by $5000 which is the cost of the reco on the box.

In the end they agreed and the car was freighted down - it arrived this afternoon.

My question is, does the fault code 4F51 EGS: 5 Gear monitoring guarantee that i need a new 'box and it is slipping or could it be caused by something else? I have seen many posts here and elsewhere where it's an electrical fault or something that causes the Trans Failsafe Prog to come up but have not been able to find any reference to the specific fault code above. BMW's answer to everything these days is just to replace the part even though it may be something else that is causing it. They did this to me what i took an SMG M3 to them, said it was the pump and wanted $5K and it turned out to be a $30 relay - they are not interested in repairing / diagnosing anything properly.

So given many of you have extensive experience in this, does the above mean i need a new box or could it be something else? If so, what?

The Trans Failsafe Prog only came up that one time and i have not had the box slip at all, not even once that i could feel. I do get the occasonal thump when stopping from 2nd - 1st but as i understand it that is common. I guess i don't want to shell out for a new box when there could be nothing wrong with it - the car drives very well and doesn't miss a beat with the transmission, shifts very well / smoothly- what are your thoughts?