Having just suffered an auto transmission failure at 42k miles - and had BMW offer a complete replacement for approx $10k, I am having it rebuilt for about $2.5k under the care of a Warranty Direct insurance policy. In my case the torque converter failed which took out the AT oil pump and the low pressure on the AT hydraulics did the rest by destroying the clutch packs. There were no warnings at all. BMW GB do not allow their dealers to repair, only replace the boxes and that adds hugely to the cost - there are expert rebuilders and the cost is about 25% of replacement.

I have had a number of conversations with the engineers who are fixing mine and it appears that the number of failures is AT's is high. BMW are not the only ones suffering premature failures with both GM and ZF boxes, nor is it limited to the luxury market alone. I have friends with Citroens, Range Rover, Ford and Merc's who have all recently suffered premature failures - in one case twice!

One mechanic thinks that the new boxes are much smarter electronically, but mechanically still weak as certain components - such as the Torque Converters & Lock Up clutches - are having to work much harder. In the 'good ol days' when AT's were three speed only things were straightforward. We now have 6,7 and even 8 speed ATs which are hugely complex (and VERY expensive) when they fail. I don't expect the overall failure rate in percentage terms is high, but I for one did not want an AT on mine but was told it would be almost unsellable in the future as the UK market for manual X5's is so low.

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