Hi - I have a 1999 523i with the auto gearbox (5 speed tiptronic).
Just recently it does not like changing up when under harder
acceleration. It will operate fine if just tootling around but as soon
as I up the pace it accelerates to the redline but refuses to change
up. I can still change up using the tiptronic mode.
The auto change in sports mode is equally troublesome.
The car has done 102,000 miles with the usual full service. No warning
lights have ever come on - it was suggested that it could be related to
the ABS sensor!!