I'm a new owner of an 04 330 CI. 107K miles. Local car. (Charlotte, NC) Two owners. I didn't purchase the car from a BMW dealer but I did have them perform a PPI. (Pre Purchase Inspection) They also were kind enough to print out the entire service history on the car. Found a few minor issues but not what I'm about to describe below.
Here is my issue. 1st thing in the morning the transmission slips in 1st gear. Reverse is fine. If I manually put the car in 2nd gear and pull away- everything is fine for the rest of the drive. Park the car for a a few hours and the cycle repeats.
The car has a GM transmission. A5S390R from best I can tell. Here is what I've done so far to try and resolve the issue:
I drained the fluid, dropped the pan, replaced the filter, cleaned things up, refilled with BMW fluid to the proper level, and still have the same problem.
The old fluid (lifetime fill) looked like motor oil that had a couple thousand miles on it. Not very dark. No major metal on the magnet. Normal gray mud.
From everything I've read on here (and I've read a bunch) it's just like the no-reverse issue except that it happens in 1st gear...