Vrroooom, CRUNCH! vrooom. Trans experts???

1990 525ia. 180,000Km

Have noticed this sporadically before, and just happened twice today. At high rpm (4000rpm), when the transmission shifts from first to second there is a noticable crunching sound during the shift. About the same loudness as the engine at 4000rpm, and lasts for the half second or so it takes the trans to shift from 1st to 2nd. Happened in Economy mode, but haven't tried it in Sport or Manual yet. I have no idea when the fluid and filter were changed, i've only had the car for 15,000k.

I'd change the fluid and filter before diagnosing it further... simple is cheap... You probably got a diptstick so it would make it easy to do your own fluid change. If so, change the filter and fluid... then drive 150km... and then just drain the fluid and refill again two more time.